Energy Efficient Building Envelope Design & Performance Assessment-Special Emphasis:Office Buildings by Shaona Dutta

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

ENERGY EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT SPECIAL EMPHASIS : OFFICE BUILDINGS PROJECT SEMINAR 01 A Project Seminar Report submitted in the partial fulfillment of the requirement for the degree of Master in Building Engineering and Management of the School of Planning and Architecture, (Deemed to be a University), New Delhi.

SHAONA DUTTA BEM/542

DEPARTMENT OF BUILDING ENGINEERING AND MANAGEMENT SCHOOL OF PLANNING AND ARCHITECTURE NEW DELHI-110002

MAY 2013

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

CERTIFICATE Certified that the seminar entitled, “E ENERGY EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT - SPECIAL EMPHASIS : OFFICE BUILDINGS”, which is being submitted by Shaona Dutta in partial fulfillment for the award of the degree of Master in Building Engineering and Management of the School of Architecture, New Delhi (deemed to be a University), is a record of the student’s own work carried out by her under my supervision and guidance.

The matter embodied in this seminar work, other than that acknowledged as reference, has not been submitted for the award of any other degree or diploma.

PROF. VAS DEV DEWAN Seminar Guide Visiting Faculty Dept. of Building Engineering and Management, School of Planning and Architecture, New Delhi.

PROF. Y.K. JAIN Head of the Department Dept. of Building Engineering and Management, School of Planning and Architecture, New Delhi.

ENERGYâ&#x20AC;&#x201C;EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

ACKNOWLEDGEMENTS The author wishes to acknowledge the contributions of the following persons for enabling her for the successful completion and presentation of this seminar work. Prof. Vas Dev Dewan, Visiting Faculty of Department of Building Engineering and Management, for his constant encouragement, invaluable guidance and motivation for carrying out this seminar work. Dr. P.C. Jain, Visiting Faculty of Department of Building Engineering and Management, for helping out in understanding the pertinence, scope and expediency of the topic. Ms. Sangita Das, Sustainability Consultant at Spectral Services Consultants Pvt. Ltd., for her advantageous suggestions, guidance and help regarding the Case Studies. Prof. Virender.K.Paul, Professor of Building Engineering and Management, for his precious suggestions and advice for carrying out the study. Dr.V.Thiruvengadam, Professor and Visiting Faculty of Department of Building Engineering and Management, for his encouragement and beneficial suggestions on this topic. Prof. Y.K.Jain, Head of the Department of Building Engineering and Management, for his constructive criticism and insightful comments in the reviews. Professionals at the site of Eco Commercial Building (ECB), Greater Noida and Delta Electronics Pvt Lts, Gurgaon.

MAY 2013

SHAONA DUTTA

ENERGYâ&#x20AC;&#x201C;EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

ABSTRACT The energy consumption of buildings is an aspect that is increasing in interest due to economical and ecological reasons as this represents a significant portion (almost 40%) of the total energy consumption of a country. One of the main ways to diminish this consumption is to reduce the energy losses, optimising the envelope of the building. This envelope is integrated by various different elements; as walls, roofs, and windows that can be different according to its orientation. For each element there are various possibilities of thermal characteristic that can be selected, as for example the insulation thickness of walls, or the kind of gassings. The report shows that the combinations of these elements based on different climate zones of the country give a very big number of possibilities that can be applied in the building industry in order to cut down the overall energy requirement.

The report also mentions about a new approach to consider the building and the envelope quality, that is the "Performance Concept". The performance of an envelope includes all aesthetic and physical properties to be fulfilled by that envelope, integrated into the function of the building as a whole.

It has been found that although office buildings have the second largest amount of buildings and floorspace, they consume the most energy of all building types, accounting for 38 percent of the total energy consumption in the bulding industry. They use a total of 1.0 quadrillion Btu of combined site electricity, natural gas, fuel oil, and district steam or hot water. It has been estimated that as much as 30% of the energy consumed in office buildings is wasted. This suggests a significant opportunity for energy use reduction, cost savings, and the mitigation of greenhouse gas emissions through cost-effective energy efficiency opportunities. To help identify the best opportunities, both from the perspective of the building owner and the utility, it is important to examine how, where, and when energy is used and the savings are likely to occur.

The report will first provide high-level energy consumption and cost metrics for the office building sector. Next, representative daily load shapes for typical small and medium office buildings will be presented, and finally, these building scenarios will be benchmarked with the LEED energy performance rating system using ASHRAE 90.1-2004 baseline in order to identify the areas of building envelope design specifying the methods through which energy consumption can be reduced.

Another focus of this study is to show the role of advanced energy simulation in the field of Building Envelope optimization. To estimate the energy requirement of the building it is necessary to make a simulation. Energy Simulation softwares simulate the energy required in a building at the conceptual design level based on the approximate footprint of the building using real time data and weather conditions of that particular place. This process also gives the measure of the energy that will be consumed in the building as per various national and international standards. Thus it helps to set a benchmark level of energy consumption for a particular type of building. The report gives an overview of eQUEST which is a DOE.2 based free building energy analysis simulation program widely used for LEED projects. The main advantages of eQUEST are mentioned below :

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings



It calculates hour by hour building energy consumption over an entire year (8,760 hours) using hourly weather data for the location under consideration.

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It also contains a dynamic daylighting model to assess the effect of natural lighting on thermal and lighting demands.

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It has a function where energy efficiency measures can be created and manipulated to see the resulting changes to a model.



It has a life cycle cost analysis tool for each ecm applied to the model.

In this report, the process of building envelope optimization using the energy simulation method of eQUEST has been discussed through the case studies of a small (Eco Commercial Building, Greater Noida) and a medium office building (Delta India Electronics ltd.) In the first case, the optimization yields 100% energy savings by using onsite photovoltaic electricity generation over the LEED mandated ASHRAE 90.1-2004 baseline and shall achieve ten (10) LEED points for Energy and Atmosphere credit 1.0. Similarly it is determined via simulation that the second building achieves 39.89% savings in Energy costs over the Basecase and shall receive Nine (9) LEED points for Energy and Atmosphere credit 1.0. The measures found by using optimization not only decrease operating costs, but also lead to better daylight usage and thermal comfort, which results in higher comfort for the building occupants. Thus the report aims at formulating a cost-effective and efficient approach in Building Envelope Design for energy conservation mainly in the commercial sector which consumes 39% of the total energy consumption of the building industry.

ENERGYâ&#x20AC;&#x201C;EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

CHAPTERIZATION 1. CHAPTER ONE : INTRODUCTION 1.1. 1.2. 1.3. 1.4. 1.5. 1.6. 1.7.

Overview of the topic Need Identification Research Goals Objectives Scope & Limitations Research Methodology Outcome of the study

2. CHAPTER TWO : LITERATURE REVIEW 2.1. 2.2. 2.3. 2.4. 2.5. 2.6.

Introduction Unpublished Reports, Theses and Seminars Published Books Codes & Standards Journals & Papers Summary

3. CHAPTER THREE : BUILDING ENVELOPE DESIGN & ENERGY EFFICIENCY 3.1.

3.2.

3.3.

3.4.

General 3.1.1. Definition 3.1.2. Elements of Building Envelope 3.1.2.1. Wall System 3.1.2.2. Fenestration System 3.1.2.3. Roofing System 3.1.3. Building Envelope & Energy Performance 3.1.3.1. Internal Heat Gain in Residential Buildings 3.1.3.2. Internal Heat Gain in Commercial Buildings 3.1.3.3. Heat Transfer in Buildings 3.1.3.4. Basic Measures for Energy Efficient Envelope Design Thermal Properties of Building Materials 3.2.1. Material Properties 3.2.2. Construction Properties 3.1.3. Building Envelope & Energy Performance Orientation 3.3.1. Reducing Solar Heat Gain in Summer 3.3.2. Allowing Solar Heat Gain in Winter 3.3.3. Quantifying the effect of Orientation Characteristics of Envelope Elements for Achieving Energy Efficiency 3.4.1. Ground Floor 3.4.2. Roofs 3.4.3. Walls 3.4.3.1. East and West Elevations 3.4.3.2. North Elevation 3.4.3.3. South Elevation

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

3.4.4.

3.4.3.4. Simulation in Wall Interventions Fenestration 3.4.4.1. Daylighting 3.4.4.2. Views 3.4.4.3. Simulation of Window Interventions

4. CHAPTER FOUR : PERFORMANCE & INTEGRATED DESIGN IN OFFICE BUILDINGS 4.1. 4.2. 4.3.

4.4.

4.5.

Introduction Overview of Design Influences Building & Site Design Features 4.3.1. Climate Features 4.3.2. Building Features Energy Conservation Measures (ECMs) 4.4.1. Envelope 4.4.2. Lighting 4.4.3. Quality Assurance 4.4.3.1. Daylighting 4.4.3.2. Interior Lighting 4.4.3.3. Exterior Lighting Multidisciplinary Co-ordination for Energy Efficiency 4.5.1. Multidisciplinary Recommendations 4.5.1.1. Define Business As Usual Baseline Buildings 4.5.1.2. Benchmarking 4.5.1.3. Budget Sharing 4.5.1.4. Investment Financial Analysis 4.5.1.5. Building Configuration & Floor Area Minimization 4.5.1.6. Schedule of Occupancy, Use & Utility Rates 4.5.2. Façade Zone Optimization 4.5.3. Performace Assessment to Promote Health & Comfort 4.5.3.1. Indoor Air Quality (IAQ) 4.5.3.2. Thermal Comfort 4.5.3.3. Visual Comfort 4.5.3.4. Acoustic Comfort 4.5.4. Budget Zoning

5. CHAPTER FIVE : DESIGN STRATEGIES & RECOMMENDATIONS FOR OFFICE BUILDINGS 5.1. 5.2.

5.3. 5.4.

Introduction Climate-Related Design Strategies 5.2.1. Hot & Dry (Rajasthan, Gujarat, Central Maharashtra, Madhyapradesh) 5.2.2. Warm & Humid (Kerala, Tamilnadu, Kolkata, Orissa & Andhrapradesh) 5.2.3. Temperate (Bangalore, Goa And Parts Of Deccan) 5.2.4. Cold (Sunny/Cloudy) (Jammu & Kashmir, Ladakh, Himachalpradesh) 5.2.5. Composite (Uttar Pradesh, Hariyana, Punjab, Jharkhand, Chattisgarh, Bihar) Climate Zone Recommendations Implementation of Recommendations 5.4.1. Envelope Components 5.4.2. Daylighting/Lighting Components

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

6. CHAPTER SIX : ADVANCED ENERGY MODELLING FOR LEED 6.1.

6.2. 6.3.

6.4.

Introduction 6.1.1. LEED Scheme 6.1.2. LEED EA Credit 1 Compliance Paths Energy Modeling Requirements Simulation Software 6.3.1. Overview 6.3.2. General Requirements DOE-2-Based Software : eQUEST 6.4.1. Introduction 6.4.2. Simulation Basics 6.4.3. Overview of the Process 6.4.4. Data Requirements 6.4.5. Computational Steps in eQUEST

7. CHAPTER SEVEN : CASE-STUDY 7A.

PRIMARY CASE STUDY – SMALL OFFICE BUILDING

7.1.

Overview of the Project 7.2.1. Project Brief 7.2.2. Brief Specifications Climatic Analysis 7.2.1. Weather Data Summary 7.2.2. Average & Record High & Low Temperature 7.2.3. Precipitation Implementation of Energy Simulation 7.3.1. eQUEST Energy Analysis 7.3.2. Simulation Results Identification of Design Parameters 7.4.1. Basic Design Parameters 7.4.2. Envelope Details 7.4.3. Details of Air Handling Units 7.4.4. Calculation of Fresh Air 7.4.5. Exterior Lighting Calculations 7.4.6. Details of Installed Solar Photovoltaic Simulation Output Summary 7.5.1. Unment Hours for Basecase at 0 Degree Rotation 7.5.2. Unment Hours for Design Case 7.5.3. Energy Cost Summary for Basecase 7.5.4. Energy Cost Summary for Proposed Case

7.2.

7.3.

7.4.

7.5.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

7B.

SECONDARY CASE STUDY – MEDIUM OFFICE BUILDING

7.6.

Overview of the Project 7.6.1. Project Brief 7.6.2. Brief Specifications Climatic Analysis 7.7.1. Weather Data Summary 7.7.2. Average & Record High & Low Temperature 7.7.3. Precipitation Implementation of Energy Simulation 7.8.1. eQUEST Energy Analysis 7.8.2. Simulation Results Identification of Design Parameters 7.9.1. Basic Design Parameters 7.9.2. Envelope Details 7.9.3. Details of Air Handling Units 7.9.4. Calculation of Fresh Air 7.9.5. Exterior Lighting Calculations 7.9.6. Details of Installed Solar Photovoltaic Simulation Output Summary 7.10.1. Unment Hours for Basecase at 0 Degree Rotation 7.10.2. Unment Hours for Design Case 7.10.3. Energy Cost Summary for Basecase 7.10.4. Energy Cost Summary for Proposed Case

7.7.

7.8.

7.9.

7.10.

8. CHAPTER EIGHT : CONCLUSIONS & RECOMMENDATIONS 8.1. 8.2. 8.3. 8.4. 8.5. 8.6. 8.7.

Overview Energy Efficiency in Buildings Optimization of Building Envelope Design Parameters Affecting Energy Performance in Buildings Advantages of Energy Simulation in Energy Efficient Building Envelope Design Deriving Design Thumb Rules for Optimum Energy Efficient Solutions for Offices Future Scope of Research Work

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

LIST OF FIGURES & TABLES Figure 1.1 Components of Building Envelope and Their Performance Assessment ........................ 14 Figure 1.2. Energy Consumption in Residential and Commercial Sector ......................................... 15 Figure 1.4. Primary energy use of buildings in different countries ...................................................... 16 Figure 1.3. Life Cycle Energy Use of Buildings ....................................................................................... 16 Figure 1.5. Use of Simulation Softwares for Building Energy Consumption ....................................... 16 Figure 1.6. Conceptual Network of Energy Efficient Building Envelope Design .............................. 19 Figure 3.1. Building Envelope .................................................................................................................. 32 Figure 3.3. Wall System Functions ........................................................................................................... 33 Figure 3.2. Basic Elements of the Exterior Wall ...................................................................................... 33 1. Exterior Cladding (Natural or Synthetic) ........................................................................................... 33 2. Drainage Plane(s) ................................................................................................................................ 33 3. Air Barrier System(s) .............................................................................................................................. 33 4. Vapor Retarder(s) ................................................................................................................................ 33 5. Insulating Element(s) ............................................................................................................................ 33 6. Structural Elements............................................................................................................................... 33 Table 3.1. Thermal Properties of different Materials............................................................................. 34 Figure 3.5. Barrier Wall Diagram ............................................................................................................. 36 Figure 3.4. Cavity Wall Diagram ............................................................................................................. 36 Figure 3.6. Mass Wall Diagram................................................................................................................ 37 Figure 3.7. schematic of Poor & Better Glazing System ...................................................................... 39 Figure 3.8. Window Size & Placement ................................................................................................... 40 Figure 3.9. Solar Control Interior Shading .............................................................................................. 41 Figure 3.10. Solar Control Glazing .......................................................................................................... 41 Figure 3.11. A Typical Green Roof Details ............................................................................................. 42 Figure 3.12. Typical Detail of Over Deck Insulation ............................................................................. 43 Figure 3.14. Some Common Techniques To Insulate Different Types Of Roofing Systems. ............ 44 Figure 3.13. Metal Roofing Systems With Over And Under Deck Insulation...................................... 44 Figure 3.15. Heat Transfer Through a Cool Roof ................................................................................... 45 Figure 3.16. Schematic showing three modes of heat transfer in Buildings– Conduction, Convection & Radiation ......................................................................................................................... 48 Table 3.2. Energy Conservation Measures for Wall, Roof and Window Design ............................... 48 Table 3.3. Values of Surface Film Resistance based on Direction of Heat Flow .............................. 51 Table 3.4. Thermal Resistances Unventilated Air Layers between Surfaces with High Emittance . 52 Figure 3.19. Sunpath in Summer and Winter ......................................................................................... 54 Figure 3.20. Using the Roof Overhang to shade the Sun in Summer ................................................. 54 Table 3.7. Effect of orientation on energy consumption for three types of building ...................... 54 Figure 3.21. Envelope Heat Flows........................................................................................................... 55 Figure 3.22. Sunpath in Summer and Winter ......................................................................................... 56 Table 3.8. Effect of wall insulation on energy consumption for three building types ..................... 57 Table 3.9. Effect of glazing interventions on energy consumption for three building types .......... 59 Figure 4.2. Heating and Cooling Influences on Building Envelope Design ...................................... 62 Figure 4.3. Energy Saving For Small & Medium Office Buildings ........................................................ 64 Figure 4.4. Annual Solar Radiation by Orientation for Office Buildings ............................................. 65 Figure 4.5. SHGC Multipliers for Permanent Projections ...................................................................... 65 Table 4.1. Typical Internal Heat Gains for Office Spaces ................................................................... 66

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Figure 4.6. Relative Impact of Energy Savings Strategies ................................................................... 67 Table 4.2. Standard Percentage Assumptions by Space Type.......................................................... 70 Table 4.3. Exterior Lighting Zones............................................................................................................ 70 Table 4.2. Guidance for Improving Energy Efficiency in Building Envelope Design........................ 76 Table 4.2. Guidance for Improving Energy Efficiency in Building Envelope Design (continued).. 77 Table 4.2. Guidance for Improving Energy Efficiency in Building Envelope Design (continued) .. 78 Table 4.3. Envelope Performance – Building Physics Related Aspects ............................................. 82 Figure 5.1. Location Map showing of Five Climate Zones of India .................................................... 94 Table 5.1. Thermal Requirements & Physical Manifestatin for different Climate Zones .................. 96 Table 6.2. Points awarded for Credit EA-1 of Optimize Energy Performance for LEED-NC v2.2 .. 105 Table 6.1. General Information on LEED Rating System .................................................................... 105 Figure 6.1. Flow chart of methodology used for energy performance assessments in LEED....... 105 Table 6.3. LEED Performance Rating Method (PRM) For Proposed and Baseline Building Models .................................................................................................................................................................. 106 Table 6.4. Details of Modeling Requirements for ASHRAE 90.1–2007 .............................................. 107 Table 6.5. Details of Modeling Requirements for ASHRAE 90.1–2007 .............................................. 108 Figure 6.2. Basic Action Panel of eQuest ............................................................................................ 110 Table 6.6. Data Requirement prior to developing the Simulation Model....................................... 111 Table 6.7. Data Requirement prior to developing the Simulation Model (Continued) ................ 112 Figure 6.3. Four basic areas for performing hourly calculations in eQUEST .................................... 113 Figure 6.4. Single Run Report on Annual Energy Consumption by End Use ................................... 123 Figure 6.5. Single Run Report on Monthly Energy Consumption by End Use ................................. 124 Figure 6.6. Single Run Report Showing Monthly Utility Bills................................................................. 125 Figure 6.7. Single Run Report on Annual Peak Demand by End Use .............................................. 125 Figure 6.8. Single Run Report on Monthly Peak Demand on End Use ............................................ 126 Figure 6.9. Comparison Report on Monthly Total Energy Consumption ......................................... 127 Figure 6.10. Comparison Report of Monthlu Utility Bills ...................................................................... 128 Figure 6.11. Comparison Report of Annual Energy by End Use ....................................................... 128 Figure 7.1. India’s First Net Zero Energy building ECB located in Greater Noida, Uttar Pradesh . 130 Table 7.1. Annual Energy Consumption chart of ECB, Greater Noida ........................................... 131 Table 7.2. Envelope Optimization Strategies applied in ECB ........................................................... 132 Figure 7.2. Energy Flow chart showing Comparison of Optimized Energy Demand and Renewable Energy Supply of ECB ....................................................................................................... 133 Figure 7.3. Ground Floor Plan of the Building ..................................................................................... 134 Figure 7.5. North side Viw of Eco Commercial Building .................................................................... 134 Figure 7.4. Detailed section of the Facade ........................................................................................ 134 Figure 7.6. Solar PV Panels on Terrace ................................................................................................ 134 Table 7.3. 24-hr Average Temperature of New Delhi ........................................................................ 135 Table 7.4. Climate Data for New Delhi ................................................................................................ 135 Table 7.5. Average Rainfall in New Delhi ............................................................................................ 135 Figure 7.8. 3D View showing Model Graphic Rendering .................................................................. 136 Figure 7.9. Schematic Section of the Building .................................................................................... 136 Figure 7.7. Representative plan showing Zoning ............................................................................... 136 BASECASE (MBTU) ................................................................................................................................... 137 Table 7.6. Energy Cost Summary for Basecase and Proposed case generated using e-QUEST Simulation ................................................................................................................................................ 138 Figure 7.13. Profile showing Loads of Lighting, Equipment and Occupancy ............................... 141

ENERGYâ&#x20AC;&#x201C;EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Figure 7.14. Comparison of Heating and Cooling Temperature Profiles ........................................ 141 Figure 7.14. LEED Platinum Rated Office Building in Gurgaon : Delta India Electronics ............... 150 Table 7.7. 24-hr Average Temperature of New Delhi ........................................................................ 152 Table 7.8. Climate Data for New Delhi ................................................................................................ 152 Table 7.9. Average Rainfall in New Delhi ............................................................................................ 152 Figure 7.15. 3D View Showing Graphic Rendering of Model using eQUEST ................................... 153 Figure 7.16. Energy-use comparison for all End uses ......................................................................... 154 Figure 7.17. Energy-use Characterization ........................................................................................... 154 Figure 7.18. Energy Use comparison for all End Uses Basecase vs Design case (1000 kWh)........ 154 Figure 7.19. Profile showing Loads of Interior & ExteriorLighting, Equipment, Occupancy, Elevator & Pumps .................................................................................................................................................. 156 Figure 7.20. Comparison of Heating and Cooling Temperature Profiles ........................................ 157 Figure 7.21. Graph showing Fan Schedule ......................................................................................... 157 Figure 7.22. Section of External Wall .................................................................................................... 157 Figure 7.23. Section of Roof .................................................................................................................. 158 Table 7.10. Lighting Details of Ground and First Floor of Delta Electronics Pvt ltd. ........................ 158 Table 7.11. Lighting Details of Second, Third and Basement Floors of Delta Electronics Pvt ltd. . 159

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

CHAPTER 1

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

1.1. OVERVIEW OF THE TOPIC “A building has a long life cycle, so its effect on the environment is a long and continuing issue to consider.” NGO, China

Building envelope is the interface between the interior of the building and the outdoor environment, including the walls, roof, fenestration and foundation which serves as a thermal barrier and plays an important role in determining the amount of energy necessary to maintain a comfortable indoor environment relative to the outside environment. Buildings are responsible for at least 40% of energy use in most countries. The absolute figure is rising fast, as construction booms, especially in countries such as China and India. It is essential to act now, because buildings can make a major contribution to tackling climate change and energy use.

ENERGY EFFICIENCY : There are three main approaches to energy neutrality: • Cut buildings’ energy demand by, for example, using equipment that is more energy efficient • Produce energy locally from renewable and otherwise wasted energy resources • Share energy – create buildings that can generate surplus energy and feed it into an intelligent grid infrastructure.

Efficiency involves reduced energy consumption for acceptable levels of comfort, air quality and other occupancy requirements, including the energy used in manufacturing building materials and in construction. Energy analysis is an integral component of sustainable building practices. Energy analysis coupled with optimization techniques may offer solutions for greater energy efficiency over the lifetime of the building. Because of the increased emissions of wastes and the depletion of fossil fuels, research and development in building technologies and integrated design processes have attained greater and renewed interest among stakeholders worldwide. Current research and development goes beyond the boundaries of building design and construction, and utilizes scientific knowledge from other fields to examine building performance.

Figure 1.1 Components of Building Envelope and Their Performance Assessment

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Energy Simulation study simulated the energy required in a building at the drawing board level of the Building Design using real time data and weather conditions of that particular place. This process also gives us the measure of the energy that will be consumed in the building as per various national and international standards. Thus it helps us to set a benchmark level of energy consumption for a particular building. To achieve sustainability, it is necessary to assess the performance of a building and its subcomponents before they are built. Many kinds of building assessment tools have been developed to support environmental decision-making, and such tools may be broadly classified as reductionists or non-reductionists tools. There are several types of reductionist tools such as economic and monetary tools, thermodynamic methods, and energy performance tools such as DOE-2, IES<VE> and ENERGYPLUS. QUICK FACTS  Residential and commercial buildings account for almost 39% of total energy consumption and 38% of carbon dioxide (CO2) emissions.  Space heating, cooling, and ventilation account for the largest amount of end-use energy consumption in both commercial and residential buildings.  In the commercial sector they are Figure 1.2. Energy Consumption in Residential and Commercial Sector responsible for 34% for energy used on site and 31% of primary energy use.  In the residential sector, space heating and cooling are responsible for 52% of energy used on site, and 39% of primary energy use.

1.2. NEED IDENTIFICATION NEED FOR ENERGY EFFICIENT BUILDING ENVELOPE DESIGN  Demand for energy is increasing fast day by day and is likely to increase in tune with industrialization/ urbanization  The building sector being one of the largest consumers of energy, has gained prominence over the past few decades. 45% of total global energy is used in heating, cooling and lighting of building. 5% energy is used in building construction.  Lack of proper benchmark in terms of total building performance.  Reduced use of non renewable sources of energy in Building industry.  Better environment stewardship using less energy and water resulting in environmental and ecological balance.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Figure 1.3. Life Cycle Energy Use of Buildings

Figure 1.4. Primary energy use of buildings in different countries

NEED FOR ENERGY SIMULATION IN BUILDING ENVELOPE DESIGN  Energy Simulation Study helps to take informed decision in the design and construction of the buildings from an Energy Consumption point of view.  This tool can be used to decide the right or optimum material and equipment specifications in a scientific and systematic manner.  Energy Modeling and Lighting Stimulation is a process to devise simulation model for optimizing energy efficiency of the proposed projects : - Building Envelope (Wall, Windows, Roof etc.) - HVAC systems and its components. - Day lighting Simulation for optimizing natural lighting and lighting controls.

Figure 1.5. Use of Simulation Softwares for Building Energy Consumption

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

1.3. RESEARCH GOALS



The goal of this topic is to develop a method to identify the optimal solution for a building envelope system so that it will perform to its maximum potential given the mix of energy sources used for heating and cooling. The topic will also highlight the selection of building envelope materials and designs based on the total environmental impact for small and medium office buildings using the newly developed simulation software, eQUEST in this case. Energy Modeling using this software should be done early in the schematic design phase to ensure that efficiency goals are met with minimal complications or costs. A preliminary model can be used at this stage to estimate savings.

1.4. OBJECTIVES



To identify the parameters of energy performance in a building envelope;



To study of energy performance appraisal methods & document their applications;

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To study & review the established energy standards & codes of the country;

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To assess the impact of energy performance of building envelope;

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To avoid resource depletion of energy, water, and raw materials;

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To propose measures for prevention from environmental degradation caused by facilities and their infrastructure throughout their life cycle;

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To study the role of energy simulation in building envelope optimization;



To propose built environments are accessible, secure, healthy, and productive.



To develop an assessment model for a specific building type (Commercial in this case) and implement its protocol and relevant design tools for all buildings.

ENERGY SIMULATION SOFTWARES : 

BLAST



Bsim



DOE – 2.1E



EnergyPlus



Energy-10



Energy Expres



Ecotect



eQUEST



ESP-r



IES <VE>



Ener-win



SUNREL



TRACE



TRNSYS



TAS

The goal of energy modelling of buildings is to accurately predict the energy use of a building to either test the energy performance of the building with regards to an established standard or to compare and contrast two buildings in order to find the total energy savings.

that

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

1.5. SCOPE & LIMITATIONS



Study of standard building codes for energy efficiency of buildings and Building Envelope performance for all types of buildings.



Study of various performance parameters like building integrity, indoor air quality, lighting quality, spatial quality, energy efficiency acoustics and building quality.



Assessment of all the building envelope performance parameters of commercial types of buildings and derive its feasibility.



Study the system of measurement of all the major performance parameters of commercial building types with special emphasis to office buildings.



Detailed Energy Modeling and Building Simulation, Defining Modeling Assumptions.



Developing Proposed and Base Case Building Simulation Model and application of energy simulation to reduce total energy consumption of small to medium & large office buildings.

SCOPE OF ENERGY SIMULATION IN BUILDING ENVELOPE DESIGN OF COMMERCIAL BUILDINGS



Energy Simulation provides an independent evaluation of the energy efficiency of the proposed new design.



Energy Simulation can provide with the most cost effective design to meet your environmental goals.



Energy Simulation quantifies the operating savings over the life of the building.



The design can be done right the first time instead of paying more to correct it later.

1.6. RESEARCH METHODOLOGY

 

Define aim, objectives, scope and limitations.

 

Study of various components of building envelope for all building types.



Propose measures for building envelope optimization of the specific building type by reducing energy consumption of buildings.



Analyze Building Envelope Performance of small to medium & large office Buildings using Energy Modelling and Simulation techniques.



Conclusion and future scope of work

Literature review of unpublished & published books, journals, codes & standards related to building envelope and its energy efficiency. Selecting a specific building typology (Commercial cum Office Building in this case) & detailed analysis of all the physical and functional factors (e.g. Thermal quantities, Lighting quality, Indoor Air Quality etc.) and their performance.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Figure 1.6. Conceptual Network of Energy Efficient Building Envelope Design

1.7. OUTCOME OF THE STUDY



Documentation, analysis and evaluation of available resources.



Fundamental concepts in energy efficient building envelope design for Commercial Buildings with special emphasis on Office Buildings and creating checklist for design parameters and performance indicators that need to be simulated.



Implementation of DOE.2 based Software – eQUEST as recommended by ASHRAE for energy modelling of the case study buildings and analyzing the methods of building envelope optimization thereafter.



Deriving thumb rules for achieving energy efficiency in Building Envelope Design of Commercial Buildings.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

CHAPTER 2

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.1. INTRODUCTION Energy-efficient Building Envelope Design & Performance Assessment using Energy Simulation, being a pretty recent topic, there is a definite lack of sufficient literature available on the subject. Since Energy efficient buildings can save energy & money the need to estimate a building’s annual energy usage or to predict or track energy usage increases which results in many seminars and papers presented on various performance levels and parameters of energy efficient building envelope design. Hence it is essential to know various programmes, studies and research papers carried out in the field to keep update of new tools and technologies for better knowledge of various performance principles of the building envelope.

UNPUBLISHED REPORTS, THESES AND SEMINARS 1. ENERGY PERFORMANCE OF BUILDING ENVELOPE AND ITS IMPACT PRESENTED BY : T.S. Deepak, 2006 2. APPROACH TO TOTAL BUILDING PERFORMANCE PRESENTED BY : Neha Prakash, 2008 3. APPLICATION OF ENERGY SIMULATION IN GREEN BUILDING PLANNING & DESIGN PRESENTED BY : Taniya Sanyal, 2008

PUBLISHED BOOKS 1. MANUAL OF TROPICAL HOUSING AND BUILDING Koenigsberger, Orient Longman 2. ENERGY EFFICIENCY IN BUILDINGS CIBSE Guide F 3. ENERGY MANAGEMENT IN BUILDINGS, 2ND EDITION Keith J. Moss 4. ENERGY SIMULATION IN BUILDING DESIGN, 2ND EDITION J. A. Clarke (Professor of Environmental Engineering University of Strathclyde Glasgow, Scotland)

CODES & STANDARDS 1. ASHRAE STANDARD 90.1 – 2010 Code for Commercial buildings (including multi-family high-rise buildings) 2. ENERGY CONSERVATION & BUILDING CODE – 2007 Energy conservation code for Residential and Commercial buildings based on climatic zones 3. ADVANCED ENERGY DESIGN GUIDE FOR SMALL TO MEDIUM OFFICE BUILDINGS– 2011 American Society of Heating, Refrigerating and Air-Conditioning Engineers The American Institute of Architects Illuminating Engineering Society of North America U.S. Green Building Council, U.S. Department of Energy 4. COMMERCIAL ENERGY CONSERVATION CODE – 2008 Based on ANSI/ASHRAE/IESNA Standard 90.1-2004 (Includes ANSI/ASHRAE/IESNA Addenda listed in Appendix F)

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

JOURNALS & PAPERS 1. ENERGY EFFICIENT BUILDING ENVELOPE DESIGNS FOR COMMERCIAL BUILDINGS Izael Da Silva; Edward Baleke Ssekulim, Strathmore University, Centre for Research in Renewable Energy and Sustainable Development, Nairobi-Kenya 2. BUILDING ENVELOPE OPTIMIZATION USING EMERGY ANALYSIS Ravi S. Srinivasan, William W. Braham, Daniel E. Campbell, D. Charlie Curcija Windows and Daylighting Group, Lawrence Berkeley National Laboratory, Berkeley CA 3. INTEGRAL BUILDING ENVELOPE PERFORMANCE ASSESSMENT Technical Synthesis Report IEA ECBCS Annex 32 4. INTELLIGENT BUILDING ENVELOPES ARCHITECTURAL CONCEPT & APPLICATIONS FOR DAYLIGHTING QUALITY Doctoral thesis for the degree of doktor ingeniør, Trondheim, November 2005, Norwegian University of Science and Technology 5. CONTRASTING THE CAPABILITIES OF BUILDING ENERGY PERFORMANCE SIMULATION PROGRAMS Drury B. Crawley, U.S. Department of Energy, Washington DC, USA Jon W. Hand, Energy Systems Research Unit, University of Strathclyde, Scotland UK 6. EFFECTIVE USE OF BUILDING ENERGY SIMULATION FOR ENHANCING BUILDING ENERGY CODES Sam C. M. Hui Department of Mechanical Engineering, The University of Hong Kong 7. ADVANCED ENERGY MODELING FOR LEED Technical Manual v2.0 September 2011 Edition

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.2. UNPUBLISHED REPORTS, THESES AND SEMINARS 2.2.1.

ENERGY PERFORMANCE OF BUILDING ENVELOPE AND ITS IMPACT PRESENTED BY : T.S. Deepak, 2006

DESCRIPTION :



The seminar deals with the energy performance of building envelope and how it affects the environment as a whole.



It studies the effect of building envelope design as a combination of roofs, walls, fenestration, external colour and texture.



It includes the study of the site, macro and micro climate, landform, water bodies, vegetation type and pattern, orientation and plan form.



The seminar also includes the study of thermo-physical properties for performance of building envelope.



It covers various energy codes of different countries which provides relevant data and standard values of various parameters of the building performance model.

RELEVANCE :  The seminar would provide various parameters and their standard values for assessing the performance of the building envelope.



It would also help in detail study of the various energy codes & standards and henceforth to draw inferences from them.

2.2.2.

APPROACH TO TOTAL BUILDING PERFORMANCE PRESENTED BY : Neha Prakash, 2008

DESCRIPTION :



The seminar deals with the total building performance approach which is basically a tool for deriving and accessing various performance levels of different building components that would ultimately help various building types to perform at their highest levels.



It describes the performance evaluation of physical factors namely Thermal performance of Building envelope and effects of Noise along with the functional factors such as Daylighting, Indoor Air Quality & Energy Efficiency.



The seminar also covers various checklists for assessing the performance factors of different components of a building.

RELEVANCE :



The seminar would provide a detailed analysis of the physical and functional performance factors and how they affect the design of a building envelope.



It also gives a brief knowledge about various approaches that can be followed to make the building envelope energy efficient.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.2.3.

APPLICATION OF ENERGY SIMULATION IN GREEN BUILDING PLANNING & DESIGN PRESENTED BY : Taniya Sanyal, 2008

DESCRIPTION :



The seminar introduces the use of energy simulation softwares and how they help in assessing the total energy consumption of a particular building.



It describes how building energy simulation can help the designers to compare various design options and lead them to more optimal and energy saving designs.



The document can assist the designers and project managers who do not have the know-how or technical expertise of a simulation expert to generate energy efficient building designs or monitor the process of design management.



It also helps to derive certain thumb rules for energy efficient design methods that emerge out of the case studies provided.

RELEVANCE :



The document would provide knowledge on energy modelling and how it helps to reduce the total energy consumption of a building by assigning proper materials and techniques in the design of the building envelope.



It also consists of sufficient data which may help to use the selected software tool to simulate the annual energy usage of the building selected for the case study.

2.3. PUBLISHED BOOKS 2.3.1. MANUAL OF TROPICAL HOUSING AND BUILDING Koenigsberger, Orient Longman. DESCRIPTION :



The manual deals with the climatic aspects of building design and shows how practical solutions are derived from theoretical understandings.



Various climatic zones and comfort levels for those particular zones have been described in this book.



The principles of thermal quantities, various means of thermal control and their respective design aspects are also a part of this manual.



The book also talks about daylighting prediction techniques, optimum lighting levels, noise problems in tropical climate, design aids and guidelines for passive design in various climatic zones.



The appendices give information on material properties, construction types, solar chart for different latitudes, Mahoney’s table etc.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.3.2. ENERGY EFFICIENCY IN BUILDINGS CIBSE Guide F DESCRIPTION :



Published in January 2004 this book has been a leading source of guidance on energy efficiency in buildings over the last few years.



The book covers both the energy requirements committed by the design and the energy costs in use, as design and management cannot be separated.



The book has three parts, details of which are provided here under : PART A : DESIGNING THE BUILDING - The design process - Developing a design strategy - Sketch design - Renewables, fuels, CHP and metering - Control strategies - Ventilation and air conditioning design - Refrigeration design - Lighting design - Heating and hot water design - Motors and building transportation systems - Electrical power systems and office equipment - Checking the design - Commissioning, handover and feedback

PART B : OPERATING AND UPGRADING THE BUILDING

- Managing the building - Acquisition and refurbishment - Maintenance and energy efficiency - Energy audits and surveys - Benchmarking, monitoring and targeting PART C : BENCHMARKS

- Energy benchmarks Appendix A1: CIBSE policy statements Appendix A2: Conversion factors and properties of fuels Appendix A3: Consultants and model briefs

2.3.3. ENERGY MANAGEMENT IN BUILDINGS, 2ND EDITION Keith J. Moss DESCRIPTION :



Published in 2006 the book talks about the estimation of energy consumption for different types of buildings such as offices, schools, factories, residences etc.



It also highlights different energy conservation strategies and their cost-benefit analysis.



The book also includes recent trends in building services such as sustainable development, whole life costing and other energy saving systems.



It also covers various checklists and benchmarks for assessing the performance indicators for different components of a building with relevant case studies.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.3.4. ENERGY SIMULATION IN BUILDING DESIGN, 2ND EDITION J. A. Clarke

DESCRIPTION :

 



Published in 2001 the book introduces the history and need for energy modelling of buildings and how these modelling methods help in optimising the total energy consumption of the building. The book has two complementary objectives : -

To cover the theoretical aspects that will be of relevance for detailed energy modeling of Buildings.

To cover the use in practice aspects that will be of relevance to those practitioners who wish to adopt a computational approach to design.

The entire edition is divided into the following few distinct chapters : - History & Overview of Simulation - Integrative Modelling Methods - Building Simulation - Processing the Building Energy Equations - Fluid Flow - HVAC, renewable energy conversion and control systems - Energy Related sub-systems - Use in Practice & Future Trends

2.4. CODES & STANDARDS 2.4.1. ASHRAE STANDARD 90.1 – 2010 Code for Commercial buildings (including multi-family high-rise buildings) DESCRIPTION :



ASHRAE 90.1 is a standard that talks about Energy conservation code for buildings, except low rise residential buildings such as 3 stories or less residential or any single-family residences Low-rise hotel, prison etc.



The main goal of releasing ASHRAE 90.1 – 2010 was 30% less energy consumption than 90.1-2004.



The standard covers the following aspects : - HVAC - Service Water Heating - Power & Lighting



Standard 90.1-2010 has a specific designation of semi-heated space and comparable thermal envelope provisions for assemblies associated with such spaces that are less rigorous than those for heated spaces.



It applies to new buildings, but also additions and alterations to existing buildings.



The standard is Required for LEED Certification and to develop energy efficient designs.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.4.2

ENERGY CONSERVATION & BUILDING CODE (ECBC) – 2007 Energy conservation code for Residential and Commercial buildings

DESCRIPTION :



The Energy Conservation Building Code (ECBC), was launched by Ministry of Power, Government of India in May 2007, as a first step towards promoting energy efficiency in the building sector.



The ECBC provides design norms for:



Building envelope, including thermal performance requirements for walls, roofs, and windows;

Lighting system, including daylighting, and lamps and luminaire performance requirements; HVAC system, including energy performance of chillers and air distribution systems; Electrical system; and Water heating and pumping systems, including requirements for solar hot-water systems.

The code provides three options for compliance:

Compliance with the performance requirements for each subsystem and system;

Building-level performance compliance.

Compliance with the performance requirements of each system, but with tradeoffs between subsystems; and

2.4.3. ADVANCED ENERGY DESIGN GUIDE FOR SMALL TO MEDIUM OFFICE BUILDINGS– 2011 American Society of Heating, Refrigerating and Air-Conditioning Engineers The American Institute of Architects Illuminating Engineering Society of North America U.S. Green Building Council, U.S. Department of Energy DESCRIPTION :



The AEDG-SMO strives to provide guidance and recommendations to reduce the total energy use in office buildings by 50% or more depending on climate, site, building use, local code jurisdiction requirements and other factors.



This Guide applies to small to medium office buildings up to 100,000 ft2 in gross floor area. Office buildings include a wide range of office-related activities and office types, such as administrative or professional offices, government offices, bank or other financial offices, medical offices without medical diagnostic equipment, and other types of offices.



These facilities typically include all or some of the following types of space usage: open plan and private office, conference meeting, corridor and transition, lounge and recreation, lobby, active storage, restroom, mechanical and electrical, stairway, and other spaces. This Guide does not consider specialty spaces such as data centers, which are more typically presented in large offices.



The primary focus of this Guide is new construction, but recommendations may be equally applicable to offices undergoing complete renovation and in part to many other office renovation, addition, remodeling, and modernization projects (including changes to one or more systems in existing buildings).

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.4.4.

COMMERCIAL ENERGY CONSERVATION CODE – 2008 Energy conservation code for Residential and Commercial buildings

DESCRIPTION :



The purpose of this code is to provide minimum requirements for the energy-efficient design of commercial and high rise buildings.



This code provides minimum energy-efficient requirements for the design and construction of new buildings and their systems, new portions of buildings and their systems, new systems and equipment in existing buildings and criteria for determining compliance with these requirements.



The provisions of this code apply to:

(a) The envelope of buildings provided that the enclosed spaces are: 1. Heated by a heating system whose output capacity is greater than or equal to 3.4 Btu/h·ft2 or 2. Cooled by a cooling system whose sensible output capacity is greater than or equal to 5 Btu/h·ft2 (b) The following systems and equipment used in conjunction with buildings: 1. Heating, ventilating, and air conditioning, 2. Service water heating, 3. Electric power distribution and metering provisions, 4. Electric motors and belt drives, and 5. Lighting.



The provisions of this code do not apply to:

(a) Single-family houses, multi-family structures of three stories or fewer above grade, manufactured houses (mobile homes) and manufactured houses (modular), (b) Buildings that do not use either electricity or fossil fuel, or (c) Equipment and portions of building systems that use energy primarily to provide for industrial, manufacturing, or commercial processes.

ENERGYâ&#x20AC;&#x201C;EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.5. JOURNALS & PAPERS 2.5.1. ENERGY EFFICIENT BUILDING ENVELOPE DESIGN FOR COMMERCIAL BUILDING Izael Da Silva; Edward Baleke Ssekulim, Strathmore University, Centre for Research in Renewable Energy and Sustainable Development, Nairobi-Kenya DESCRIPTION : Commercial Buildings are amongst the major consumers of energy in any country most of which is utilized within buildings, thus a thorough critique of the building envelope is necessary to reduce energy wastage within them. The aim of this paper is to present findings of the comparative study carried out on Commercial buildings at Strathmore University - Nairobi, Kenya and Makerere University-Kampala, Uganda. The study mainly considered the effect of building envelope designs and orientation to the energy consumption of the buildings. ECOTECT, a Building energy performance analysis tool was employed to quantify the effect of both the conventional and Energy Efficient Building Envelopes to the overall energy consumption of the buildings.

The research findings show that the overall energy consumption of Comercial buildings could easily be reduced by about 40% through the design of envelopes suited to the micro-climate of the particular site, proper selection of construction materials vis-avis their thermal performance, extensive use of daylighting, wise utilization of water and good building waste management systems as well as utilization of Energy Efficient Appliances within the building. The study also revealed that integration of a Building Management System would significantly reduce resource utilization within the building.

2.5.2. INTELLIGENT BUILDING ENVELOPES ARCHITECTURAL CONCEPT & APPLICATIONS FOR DAYLIGHTING QUALITY Doctoral thesis for the degree of doktor ingeniĂ¸r, Trondheim, November 2005, Norwegian University of Science and Technology DESCRIPTION : During the past few decades, buildings have been imposed to steadily extend their functionality at diminishing cost. Increasingly varying and complex demands related to user comfort, energy and cost efficiency have lead to an extensive use of mechanical systems to create a satisfactory indoor climate. The expanding application of control technology in this context has lead to the emergence of the terms intelligent building and intelligent building envelope to describe a built form that can meet such demands, be it to a varying degree of success. A multitude of definitions of intelligent building envelopes, however, opens for divergent interpretations of the design, operation and objectives of this type of envelope. Within the scope of this research, intelligent behaviour for a building envelope is, similar to human intelligent behaviour, defined as adaptiveness to the environment by means of psychical processes of perception, reasoning and action, which enables the envelope to solve conflicts and deal with new situations that occur in its interaction with the environment.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.5.3. EFFECTIVE USE OF BUILDING ENERGY SIMULATION FOR ENHANCING BUILDING ENERGY CODES Sam C. M. Hui Department of Mechanical Engineering, The University of Hong Kong DESCRIPTION : Building energy simulation is playing an increasingly important role in building energy codes. This paper investigates the important underlying issues affecting the use of building energy simulation for enhancing building energy codes. The background and development of building energy codes is described. The rationale and important issues of performancebased building energy codes are explained. The practical building design and essential simulation skills are presented. Finally, the key factors affecting the effectiveness and validity of the simulation approach are discussed.

2.5.4. ADVANCED ENERGY MODELING FOR LEED Technical Manual v2.0 September 2011 Edition DESCRIPTION : Energy performance is a critical element of integrated design for green buildings. The LEED Rating System acknowledges its importance with the minimum efficiency requirements associated with Energy and Atmosphere Prerequisite 2, Minimum Energy Performance, and the significant emphasis on points assigned to Energy and Atmosphere Credit 1, Optimize Energy Performance.

The manual consists of five chapters and four appendixes. Readers may find certain sections in the manual particularly useful based on their degree of familiarity with the referenced standards, such as ASHRAE 90.1–2007, and their energy modeling skills. Critical tools and guidance for advanced users include the following:



A comparative summary of energy modeling requirements for baseline and proposed design models for ASHRAE Standard 90.1–2007, Appendix G, and California Title 24-2005,



Critical steps recommended for verification of energy savings for EA Prerequisite 2 and EA Credit 1,

 

Input quality control checklist, with common ASHRAE 90.1–2007 errors, and Input-output consistency checklist (Chapter 3, Table 3.3).

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

CHAPTER 3

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

2.6. GENERAL 3.1.1. DEFINITION The building envelope refers to the exterior façade, and is comprised of opaque components and fenestration systems. It contains those elements of the building that form the boundary between the indoor environment of a building and the external environment, thus protect the building‘s interiors and occupants from the weather conditions and shield them from other external factors e.g: noise, pollution, etc. Envelope design strongly affects the visual and thermal comfort of the occupants, as well as energy consumption in the building. Building envelope is comprised of opaque components and fenestration systems. OPAQUE COMPONENTS Walls, roofs, slabs on grade (in touch with ground), basement walls, opaque doors FENESTRATION SYSTEMS

Figure 3.1. Building Envelope

Windows, skylights, ventilators, and doors that are more than one-half glazed A well designed building envelope not only helps in complying with the Energy Conservation Building Envelope but can also result in first cost savings by taking advantage of daylighting and correct HVAC sizing. The commonly considered elements of building envelope are: 1. Walls 2. Window 3. Roof

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

3.1.2. ELEMENTS OF BUILDING ENVELOPE As mentioned earlier the Building Envelope consists of four basic elements :

   

Wall System Fenestration System Roofing System Atria System

3.1.2.1. WALL SYSTEM Exterior wall types commonly associated with above-grade, Building Envelope design and construction can generally be classified as follows : Cavity Wall Barrier Wall Mass Wall

Figure 3.2. Basic Elements of the Exterior Wall 1. Exterior Cladding (Natural or Synthetic) 2. Drainage Plane(s) 3. Air Barrier System(s) 4. Vapor Retarder(s) 5. Insulating Element(s) 6. Structural Elements

Figure 3.3. Wall System Functions

Each of the above wall types, or combination thereof, generally consists of the following basic elements, or layers:

     

Exterior Cladding (Natural or Synthetic) Drainage Plane(s) Air Barrier System(s) Vapor Retarder(s) Insulating Element(s)

Structural Elements These various wall types are discussed in brief in the next few pages.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

THERMAL STORAGE / THERMAL CAPACITY



Thermal capacity is the measure of the amount of energy required to raise the temperature of a layer of material, it is a product of density multiplied by specific heat and volume of the construction layer.



The capacity to store heat depends upon the mass and therefore on the density of the material as well as on its specific heat capacity.



High density materials such as concrete, bricks, stone are said to have high thermal mass owing to their high capacity to store heat while lightweight materials such as wood, or plastics have low thermal mass.



The heat storing capacity of the building materials help achieve thermal comfort conditions by providing a time delay. This thermal storage effect increases with increasing compactness, density and specific heat capacity of materials.



Thermal performance of walls can be improved by following ways: 1. Increasing wall thickness 2. Providing air cavity between walls and hollow masonry blocks 3. Applying insulation on the external surface. 4. Applying light coloured distemper on the exposed side of the wall.

CONDUCTANCE -

Conductivity (K) is defined as the rate of heat flow through a unit area of unit thickness of the material, by a unit temperature difference between the two sides.

The unit is W/mK (Watt per metre - degree Kelvin).

The conductivity value varies from 0.03 W/mK for insulators to 400W/mK for metals.

Materials with lower conductivity are preferred, as they are better insulators and would reduce the external heat gains from the envelope.

WALLS-INSULATION -

Thermal insulation is of great value when a building requires mechanical heating or cooling insulation helps reduce the space-conditioning loads.

Location of insulation and its optimum thickness are important.

In hot climate, insulation is placed on the outer face of the wall so that thermal mass of the wall is likely coupled with the external source and strongly coupled with the interior.

Thermal properties of these materials are given below: Material

Conductivity (W/m K)

Specific Heat Capacity (KJ/ Kg. K)

Density (Kg/m3)

Brick

0.811

0.88

1820

Mud

0.750

0.88

1731

Stone

1.5

0.84

2200

Timber

0.072

1.68

480

Table 3.1. Thermal Properties of different Materials

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

AIR CAVITIES



Air cavities within walls reduce the solar heat gain factor, thereby reducing space-conditioning loads.



The performance improves of the void is ventilated. Heat is transmitted through the air cavity by convection and radiation.



A cavity represents a resistance, which is not proportional to its thickness. For a thickness >20mm, the resistance to heat flow remains nearly constant.



Ventilated air does not reduce radiative heat transfer from roof to ceiling. The radiative component of heat transfer may be reduced by using low emissivity or high reflective coating (E.g.: aluminum foil) on either surface facing the cavity.



With aluminium foil attached to the top of ceiling, the resistance for downward heat flow increases to about 0.4m2k/W, compared to 0.21m2k/M in the absence of the foil.

3.1.2.1.1 TYPES OF WALL SYSTEMS CAVITY WALL A cavity wall (also referred to as "screen" or "drained" wall systems) is considered by many to be the preferred method of construction in most climatic and rainfall zones in our country. This is due primarily to the pressure-equalization that can be achieved, and the redundancy offered by this type of wall assembly to resist uncontrolled, bulk rainwater penetration. A term commonly used to describe clay brick and/or concrete masonry wall systems installed over a largely open, unobstructed air space/drainage cavity, this term is now used more generically to define any wall system or assembly that relies upon a partially or fully concealed air space and drainage plane to resist bulk rainwater penetration and, depending upon the design, to improve the overall thermal performance at the building enclosure. Drained cavity walls typically include the following general characteristics:



An exterior cladding element that is intended to either shed or absorb the majority of bulk rainwater penetration before it enters the concealed spaces of the wall assembly (the initial, though not primary, line of defense against rainwater penetration in this type of wall assembly).



A drainage cavity, or air space, that is intended to collect and control rainwater that passes through the exterior cladding element and re-direct that water to the building exterior. The cavity may be ventilated for pressure equalization, either mechanically or passively, to facilitate this process by preventing negative pressure that may draw rainwater across the cavity into the "dry" sections of the wall assembly via anchors, wall ties, and similar penetrations).



An internal drainage plane that is intended to function as the primary line of defense against uncontrolled rainwater penetration. This layer serves functionally as the dividing line between the "wet" and "dry" sections, or "zones," of the exterior wall assembly. This layer can be created using a variety of both dry sheet-good or wet, trowel-applied products depending upon the climate in which the building is to be located and the desired level of vapor permeability necessary to prevent condensation and potential mold growth on the dry side of the exterior wall assembly.



An insulating layer, which can be located either inboard or outboard of the internal drainage plane depending upon the geographic region and climate in which the building or structure is to be located.

ENERGYâ&#x20AC;&#x201C;EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Although a drained cavity wall offers many advantages over the other three types of exterior wall systems discussed in this section, it should be noted that an improperly designed and executed cavity wall system can be very disruptive and costly to properly and effectively repair after construction is complete. Corrosion of mild steel wall ties, structural connections and related wall elements, together with interior mold growth, often remain concealed from view in this type of wall system, and can continue for a period of years before manifesting themselves in a location that can be readily observed and remediated. Furthermore, because the primary drainage plane and many of the most critical interface details are often concealed inside the wet zone in this type of wall system, direct intervention and repair of these elements can be highly invasive and disruptive to an occupied building, and will often negatively impact the overall appearance of the building. To mitigate these concerns, a comprehensive building envelope quality assurance program similar to the program discussed later in this section is often considered extremely desirable with this type of wall system in order to ensure that critical cavity wall elements are properly designed and effectively installed at the time of original construction. In pressure-equalized, "rainscreen" cavity wall systems, the primary drainage plane, and principal air barrier are located in the same plane between the wet and dry zones of the wall assembly. In colder climates, the insulation is also placed outboard of the innermost (primary) drainage plane in this type of wall assembly, inside the wet zone (drainage cavity) of the wall. This approach, which dates back to the 1960's in North America, can be extremely effective in resisting uncontrolled, bulk rainwater penetration. However, the principal advantage of this system, which is to prevent a negative air pressure differential from occurring across the exterior wall assembly (a condition that can "draw" rainwater through the enclosure and into the building), can also be extremely difficult to effectively achieve in the field. This is due primarily to the relatively complex detailing often required at exterior wall penetrations through the concealed air barrier and primary drainage plane, and the correspondingly high level of workmanship required to effectively seal those conditions to prevent the flow of unconditioned air inward across the exterior wall assembly.

Figure 3.4. Cavity Wall Diagram

Figure 3.5. Barrier Wall Diagram

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BARRIER WALL As the name implies, this term is commonly used to describe any exterior wall system of assembly that relies principally upon the weather-tight integrity of the outermost exterior wall surfaces and construction joints to resist bulk rainwater penetration and/or moisture ingress. This type of wall system is commonly associated with precast concrete spandrel panels, certain types of composite and solid metal plate exterior cladding systems, and early generation exterior insulation and finish systems (EIFS). Although often considered a more cost-effective and, therefore, desirable alternative to either cavity or mass walls assemblies, barrier walls are cause for some concern in that they: a) offer only a single line of defense against bulk rainwater penetration; b) often include relatively complex interface details that require a level of workmanship in the field that is beyond the capabilities of the individual trades, and; c) require a relatively high degree of routine maintenance to remain effective in the long term, resulting in increased long-term maintenance costs. In short, this system can arguably be considered a "zero tolerance" wall system, whereby any defect in design, installation, or workmanship can result in immediate and direct rainwater penetration into the dry zone of the exterior wall system or assembly and, more critically, the conditioned spaces of a building or structure. MASS WALL Unlike a cavity wall system, where the wall is constructed with a wall cavity and through-wall flashing to collect and redirect bulk rainwater to the building exterior, mass walls rely principally upon a combination of wall thickness, storage capacity, and (in masonry construction) bond intimacy between masonry units and mortar to effectively resist bulk rainwater penetration. For economic reasons, mass walls are less common in design and construction today. However, when constructing an addition, or incorporating a portion of an existing building into a new building or structure, the design and behavior of mass walls relative to storage capacity and both heat and moisture transfer must be understood by the design professional. In addition to bulk rainwater penetration and moisture ingress that is often difficult to track (and therefore effectively isolate and repair) in this type of wall construction, the potentially negative effects of drying must also be considered when designing around or otherwise restoring this type of wall system. Evaporative drying across this type of wall assembly, either to the interior or exterior, can contribute to efflorescence (soluble salts deposited at or near the wall surface, which can lead to visible discoloration and spalling), deterioration of interior portland cement plaster finishes (a relatively common finish in mass walls constructed in the early 20th century), and organic/microbial growth on either the interior or exterior exposed wall surfaces.

Figure 3.6. Mass Wall Diagram

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3.1.2.2. FENESTRATION SYSTEM Fenestration system can be divided into three major parts : Glazing, Windows & Sloped Glazing

3.1.2.2.1. GLAZING



Glass has been used for thousands of years to allow daylight into our buildings, while providing weather protection. The vast majority of new windows, curtain walls and skylights for commercial building construction have insulating glazing for energy efficiency and comfort.



Larger the windows, the more important glazing selection and shading effectiveness are to control glare and heat gain.



The most commonly glazing material used in openings is glass, although recently polycarbonate sheets are being used for skylights.



Internal shading devices such as curtains, or blinds could reflect back some of that energy outside the building.



The primary properties of glazing that impact energy are: Visible reflectance (affecting heat and light reflection) Thermal transmittance or U - value (affecting conduction heat gains) Solar heat gain (affecting direct solar gain) Spectral selectivity (affecting daylight and heat gain) Glazing colour (affects the thermal and visual properties of glazing systems and thus energy usage)

o o o o o



An ideal spectrally selective glazing admits only the part of the sun’s energy that is useful for day lighting.

The following covers brief descriptions of commonly used glass and glazing components: ARCHITECTURAL GLASS comes in three different strength categories. Annealed glass is the most commonly used architectural glass. Because it is not heat-treated and therefore not subject to distortion typically produced during glass tempering, it has good surface flatness. On the downside, annealed glass breaks into sharp, dangerous shards. Heat-strengthened and fully-tempered glass are heat-treated glass products, heated and quenched in such a way to create residual surface compression in the glass. The surface compression gives the glass generally higher resistance to breakage than annealed glass. Heat-strengthened glass has at least twice the strength and resistance to breakage from wind loads or thermal stresses as annealed glass. The necessary heat treatment generally results in some distortion compared to annealed glass. Like annealed glass, heat-strengthened glass can break into large shards. Fully-tempered glass provides at least four times the strength of annealed glass, which gives it superior resistance to glass breakage. Similar to heat-strengthened glass, the heat-treatment generally results in some distortion. If it breaks, fully-tempered glass breaks into many small fragments, which makes it suitable as safety glazing under certain conditions.

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LAMINATED GLASS consists of two or more lites of glass adhered together with a plastic interlayer. Because it can prevent the fall-out of dangerous glass shards following fracture, it is often used as safety glazing and as overhead glazing in skylights. The plastic interlayer also provides protection from ultraviolet rays and attenuates vibration, which gives laminated glass good acoustical characteristics. Because laminated glass has good energy absorption characteristics, it is also a critical component of protective glazing, such as blast and bullet-resistant glazing assemblies. See Building Envelope Design Resource Page Blast Safety for more information. COATED GLASS is covered with reflective or low-emissivity (low-E) coatings. In addition to providing aesthetic appeal, the coatings improve the thermal performance of the glass by reflecting visible light and infrared radiation. TINTED GLASS contains minerals that color the glass uniformly through its thickness and promote absorption of visible light and infrared radiation. INSULATING GLASS UNITS consists of two or more lites of glass with a continuous spacer that encloses a sealed air space. The spacer typically contains a desiccant that dehydrates the sealed air space. The air space reduces heat gain and loss, as well as sound transmission, which gives the ig unit superior thermal performance and acoustical characteristics compared to single glazing. Most commercial windows, curtain walls, and skylights contain ig units. Most perimeter seals consist of a combination of non-curing (typically butyl) primary seal and cured (frequently silicone) secondary seal. The service life of an ig unit is typically determined by the quality of the hermetic sealants installed between the glass and the spacers, and the quality of the desiccant.

Figure 3.7. schematic of Poor & Better Glazing System

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3.1.2.2.2. WINDOWS



Windows are very important component of the building envelope, in addition to providing physical and visual connection to outside.



Solar radiation coming in through windows provides natural lighting, natural air and heat gain to the space inside.



The main purpose of a building and its windows is to provide thermal and visual comfort to the occupants and if this can be achieved using less energy, so much the better.



Proper location, sizing, and detailing of windows and shading form are important part of the bioclimatic design as they help to keep the sun and wind out of building or allow them when needed.



Primary components of a window which have significant impact on energy and cost of the building for which guidelines are provided in this section are as follows: A. Window size, placement B. Frame C. Shading (external & internal)

A. WINDOW SIZE, PLACEMENT HEIGHT OF WINDOW HEAD: The higher the window head, the deeper will be the penetration of daylight. SILL HEIGHT (HEIGHT FROM FLOOR TO THE BOTTOM OF THE WINDOW): The optimum sill for good illumination as well for good ventilation should be between the illumination workspace and head level of a person. Carrying out any task, the suitable work plane levels are to be 1.0 to 0.3 m high respectively.

Figure 3.8. Window Size & Placement

B. FRAME



The type and quality of window frame affects a window‘s air infiltration and heat gain / heat loss characteristics. There are three kinds of framing material mostly used which are metal, wood and polymers.



Wood has a good structural integrity and insulating values but low resistance to external weather conditions.



Metal frames have poor thermal performance, but have excellent structural characteristics and durability.



Aluminium is the most preferred metal for frames, but it is highly conductive and its thermal performance can be improved with a thermal break (a non metal component which separates the metal frame exposed to the outside from surfaces exposed to the inside.)



Vinyl window frames which are primarily made from polyvinyl chloride (PVC) offer many advantages. Available in wide range of style and shapes PVC frames has high R– value (Resistance value) and low maintenance.

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C. SHADING



Day lighting is utilization of light from the sun and sky to complement or replace electric light.



Appropriate fenestration and lighting controls can be used to modulate daylight admittance and to reduce electric lighting, while meeting the occupants‘ visual comfort.



Buildings, in which artificial lighting is integrated with the day lighting, can reduce their energy bills significantly.



Good day lighting in a building depends upon the following factors – External shading Internal shading Solar control glass

o o o

INTERNAL SHADING DEVICES



If properly adjusted, they can allow diffuse sunlight to penetrate inside the space.



They don’t keep solar heat out, not provided over external shading



Good shading devices also reduce cooling loads. They also modify the intensity and distribution of daylight entering the space.

Figure 3.9. Solar Control Interior Shading

SOLAR CONTROL GLAZING Solar control glazing is very effective against heat flow across the window but can reduce transmission of light inside the space. LIGHT SHELVES



The function of light shelf is to protect the occupants from direct sunlight in summer and allow sufficient light in winter.



The light shelf is placed above the eye level so that reflections do not get into eyes of occupants. Uniform daylight is also



The light shelf should be sufficiently projected outside so as to protect the window.



The angle of the light shelf is also important as tilting helps in deeper light penetration but also reflects light back.

 

The finishes should be reflective as matte surface reflects back about half light backwards

Figure 3.10. Solar Control Glazing

The top of the shelf should be matte white or diffusely specular, and not visible from any point in the room.

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3.1.2.3. ROOFING SYSTEM Conventional Roof Insulation Practices In India Roof Insulation with conventional materials like Foam Concrete, Mud Faska, Brick Bat Coba has been practiced since ages. However these products are quite heavy and add dead load to the roof slab. Moreover the thermal conductivity value is very high which results into higher thickness application without much benefit. These products have the tendency to develop cracks and as a result water absorption takes place. Moreover, the products are open cell and porous type which results into water absorption. This application also calls for good workmanship. ROOFING PRODUCTS Products for low-slope roofs, found on commercial and industrial buildings fall into two categories: single-ply materials and coatings. Single-ply materials are large sheets of pre-made roofing that are mechanically fastened over the existing roof and sealed at the seams. Coatings are applied using rollers, sprays, or brushes, over an existing clean, leak-free roof surface. Products for sloped roofs are currently available in clay, or concrete tiles. These products stay cooler by the use of special pigments that reflect the sun‘s infrared heat. In India, lime coats, white tiles grouted with white cement, special paints, etc. are used as cool roofing materials. ENERGY EFFICIENT ROOF INSULATIONS The roof requires significant solar radiation and plays an important role in heat gain/losses, day lighting and ventilation. Depending on the climatic needs, proper roof treatment is essential. In a hot region, the roof should have enough insulating properties to minimize heat gains. A few roof protection methods are as follows: A cover of decidous plants or creepers can be provided. Evaporation from roof surfaces will keep the rooms cool. The entire roof surface can be covered with inverted earthen pots. It is also an insulated cover of still air over the roof shading device. This can be mounted close to the roof in the day and can be rolled to permit radiative cooling at night. The upper surfaces of the canvas should be painted white to minimize the radiation absorbed by the canvas and consequent conductive heat gain through it Effective roof insulation can be provided by using vermiculite concrete. Heat gains through roofs can be reduced by adopting the following techniques. GREEN ROOF CONCEPT A roofing system through shading, insulation, evapotranspiration and thermal mass, thus reducing a building‘s energy demands for space conditioning. The green roof moderates the heat flow through the roofing system and helps in reducing the temperature fluctuations due to changing outside environment. Green roof is a roof of a building that is partially or completely Figure 3.11. A Typical Green Roof Details covered with vegetation and soil that is planted over waterproofing membrane. If widely used green roofs can also reduce the problem of urban heat island which would further reduce the energy consumption in urban areas.

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USE OF HIGH REFLECTIVE MATERIAL ON ROOF TOP Use light coloured roofs having an SRI (solar reflectance index) of 50% or more. The dark coloured, traditional roofing finishes have SRI varying from 5 - 20%. A good example of high SRI is the use of broken china mosaic and light coloured tiles as roof finish, which reflects heat off the surface because of high solar reflectivity and infrared emittance, which prevents heat gain and thus help in reducing the cooling load from the building envelope. If the roof is exposed to Solar heat it will input continuous heat inside the building which in turn will add to the A.C. machinery load. This concept of protecting the roof is termed as Roof Insulation. There are many different types of insulation materials to choose from when applying on a commercial roof or reproofing an existing structure. The function of roof insulation is to insulate the building against heat in flow from outside during the day. USE OF HIGHER ALBEDO MATERIALS Higher albedo materials can significantly reduce the heat island effect. Higher the albedo larger will be the amount of solar radiation reflected back to the sky. Roofs provided with high reflective coatings remains cooler than those with low reflectance surfaces and are known as cool roofs. Cool roofs can reduce the building heat gain and can save the summertime air conditioning expenditures. These paints are highly efficient, energy-saving, flexible coatings, made from water based pure acrylic resin system filled with vacuumed sodium borosilicate ceramic micro spheres of less than 100 microns in size. Each micro sphere acts as a sealed cell and entire mastic acts as a thermally efficient blanket covering the entire structure. These coatings are non-toxic, friendly to the environment, and form a monolithic (seamless) membrane that bridges hairline cracks. They are completely washable and resist many harsh chemicals. Roof Coats have high reflectance and high remittance as well as a very low conductivity value. They offer UV protection and low VOC's. They display excellent dirt pick-up resistance and retain their flexibility after aging. These roof Coats reduce noise transmission and have an effective use range from -40 Deg C to 375 Deg C. THERMAL INSULATION FOR ROOF Well insulated roof with the insulation placed on the external side is an effective measure to reduce solar heat gains from the roof top. The insulated materials should be well protected by water proofing. For air conditioned spaces, Energy Conservation Building Code (ECBC) recommends the thermal performance for external roof for all the five climate zones in India. OVER DECK INSULATION In this system a thermal barrier or insulation is provided over the RCC, so that the heat of the sun is not allowed to reach the RCC slab of the roof at all. In this way we can preserve the RCC from getting heated up Once the RCC is heated up there is no other way for the heat to escape other than inside the building So ever though the thermal barrier is provided under the RCC, as in underdeck insulation, some heat passes through it and heats up the ambience of the room. This decreases the comfort level of the room and if the building is centrally AC, increases the AC load. Hence we can safely conclude that overdeck insulation has its own

Figure 3.12. Typical Detail of Over Deck Insulation

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advantages over underdeck insulation. Overdeck Insulation material should have adequate compression resistance, low water absorption, resistance to high ambient temperature and low thermal conductivity. Overdeck insulation applications are carried out by either –  Preformed insulation materials  In-situ application A) Preformed insulation material : Preformed Insulation material are further classified as under :

   

Expanded Polystyrene slabs Extruded Polystyrene slab Polyurethane / Polyisocyanurate slabs Perlite boads

B) In-situ application



Spray applied Polyurethane

Figure 3.14. Some Common Techniques To Insulate Different Types Of Roofing Systems.

Figure 3.13. Metal Roofing Systems With Over And Under Deck Insulation

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COOL ROOF Depending on the material and construction, a roof will have different properties that determine how it conducts heat to the inside of the building. Cool roofs are roofs covered with a reflective coating that has a high emissivity property that is very effective in reflecting the sun‘s energy away from the roof surface. These ―cool roofs‖ are known to stay 10°C to 16°C cooler than a normal roof under a hot summer sun; this quality greatly reduces heat gain inside the building and the cooling load that needs to be met by the HVAC system. Box below discusses how solar heat radiation is reflected, absorbed and emitted from the roof and how these concepts are used in developing cool roofs.

Figure 3.15. Heat Transfer Through a Cool Roof

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3.1.3. BUILDING ENVELOPE AND ENERGY PERFORMANCE The building envelope is in a sense a filter between the internal and external environments. It serves to protect the indoor spaces from undesirable impacts such as excessive cold, heat, radiation, and wind, while allowing desirable impacts to pass through such as cool breezes on a hot day, warmth from the sun on a cold day, daylight, etc. The building envelope directly influences the energy performance of a building in the following ways:

      

Resisting undesirable heat transfer. Allowing desirable heat transfer. Providing heat storage (delayed heat transfer). Allowing daylight penetration. Preventing undesirable light penetration (glare). Allowing desirable ventilation. Preventing undesirable ventilation.

Essentially there are two different approaches to envelope design in relation to building energy performance. APPROACH 1 One approach seeks to isolate the interior of the building as much as possible from the external environment. Insulation is used extensively in all the envelope elements to reduce heat transfer as far as possible. Such buildings rely entirely on air conditioning systems to provide heating or cooling to maintain comfort conditions. This is often referred to as an ‘active’ approach to building energy design. APPROACH 2 This approach to building energy design is referred to as “passive” design. This seeks to encourage beneficial interactions between the building and the outside environment, while reducing as far as possible the undesirable interactions. In climates, where the average daily temperature is generally close to indoor comfort conditions, this approach tends to make use of thermal mass to reduce the extremes of day and night temperature. Careful use of both insulating and conductive materials as appropriate for different elements of the building prevent or encourage heat transfer when it is useful, and controlled ventilation allows air movement through the building to provide fresh air and help to keep the temperature in the comfort zone. When successful, this approach can allow the external environment to address some or all of the internal loads, reducing the energy required by mechanical systems. Cooling of the building takes place when heavy elements such as walls absorb heat from the building during the day and release it to outside at night. Ventilation of the building when the outdoor air is cool can also help to cool the building. In winter heat from the sun can be stored in the walls and released into the building at night when heating is needed. When it fails, this approach can lead to high energy consumption if mechanical systems are required to pump heat into or out of thermal mass elements that conflict with the desired internal temperature.

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3.1.3.1. INTERNAL HEAT GAIN IN RESIDENTIAL BUILDINGS Generally buildings such as residential houses with relatively low levels of internal heat gain from occupants, lights and equipment, can be designed using passive principles to achieve comfort conditions for most of the year with little or no mechanical heating or cooling.

3.1.3.2. INTERNAL HEAT GAIN IN COMMERCIAL BUILDINGS Buildings with high levels of internal heat gain such as office blocks will generally require mechanical systems to maintain comfort conditions, but there are significant opportunities to reduce the energy consumption with careful design. In the design of energy efficient buildings dominated by internal heat gains particular attention should be given for matching the mechanical systems to the internal loads, and to ensure that control systems are designed and operated to avoid conflict between the mechanical systems and the thermal mass elements of the envelope and internal structure. For buildings with little internal heat gain from occupants and equipment, it is found that the energy needed for heating in winter is similar to or even greater than the energy needed for cooling in summer. Even in summer, there is opportunity for buildings to loose heat to the environment through the walls and roof at night, and through the floor at all times of day. The result is that the optimal interaction between building and environment is quite complex, and certainly not as simple as providing maximum insulation all round, as may be the case in climates that are generally either too cold or too hot.

3.1.3.3. HEAT TRANSFER IN BUILDINGS Heat transfer takes place through walls, window and roofs in buildings from higher temperature to lower temperature in three ways : Conduction Convection Radiation Conduction, also called diffusion, is the direct microscopic exchange of kinetic energy of particles through the boundary between two systems. When an object is at a different temperature from another body or its surroundings, heat flows so that the body and the surroundings reach the same temperature, at which point they are in thermal equilibrium. Such spontaneous heat transfer always occurs from a region of high temperature to another region of lower temperature, as described by the second law of thermodynamics. Conductive heat transfer across the building envelope also depends upon the conductivity of the building material used. Different materials offer different thermal resistance to the conduction process. Individually walls and roofs are comprised of a number of layers composed of different building materials. Thus it is important to establish over all thermal resistance and heat transfer coefficient (U factor), also known as Thermal Transmittance. The concept of thermal resistance and Ufactor are discussed later in this chapter. Convection occurs when bulk flow of a fluid (gas or liquid) carries heat along with the flow of matter in the fluid. The flow of fluid may be forced by external processes, or sometimes (in gravitational fields) by buoyancy forces caused when thermal energy expands the fluid (for example in a fire plume), thus influencing its own transfer. The latter process is often called "natural convection". All

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convective processes also move heat partly by diffusion, as well. Another form of convection is forced convection. In this case the fluid is forced to flow by use of a pump, fan or other mechanical means. The last major form of heat transfer is by radiation, which may occur through a vacuum or some transparent medium (solid or fluid). It is the transfer of energy by means of photons in electromagnetic waves in much the same way as electromagnetic light waves transfer light (albeit at different wavelengths). The same laws that govern the transfer of light (e.g. its speed) govern the radiant transfer of heat.

Figure 3.16. Schematic showing three modes of heat transfer in Buildings– Conduction, Convection & Radiation

3.1.3.4. BASIC MEASURES FOR ENERGY EFFICIENT ENVELOPE DESIGN HEAT/MOISTURE LOSSES

WALLS

ROOF

WINDOW

Minimize conduction losses

Use insulation with low U-value

Marerial with low Uvalue to be used

Minimize convection losses & Moisture penetration

Reduce air leakage & use vapor barrier

Prefabricated window and seal the joints between windows and walls to be used

Minimize Radiation Losses

Use light coloured coating with high reflectance

Glazing with low SHGC to be used

Table 3.2. Energy Conservation Measures for Wall, Roof and Window Design

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3.2. THERMAL PROPERTIES OF BUILDING MATERIALS Thermal properties of building materials include those that are related to a particular material irrespective of its dimensions and location, and properties that relate to the material or groups of materials in a particular configuration as it is used in a building. The first group are described below under ‘material properties’. The second are described under ‘construction properties’.

3.2.1. MATERIAL PROPERTIES

Figure 3.17. Mechanisms of Heat Transfer through Building Envelope.

Building materials can conveniently be considered in two categories; opaque and translucent. Opaque materials are those that do not allow transmission of light or thermal radiation. They include typical wall materials such as bricks, concrete, timber, metals and fibre insulation. The properties of opaque building materials that are most relevant to the thermal performance include the following :

   

Thermal conductivity. Thermal resistivity. Specific heat capacity. Density.

Translucent materials are those that allow the transmission of light or thermal radiation. They include materials such as glass and plastics used in windows, curtain walling and skylights. In addition to the properties of opaque materials, it is important to know the transmissivity of translucent materials. 3.2.1.1. THERMAL CONDUCTIVITY Thermal conductivity is a measure of the ability of a material to transfer heat by conduction. It is measured in units of [W/m.K]. 3.2.1.2. THERMAL RESISTIVITY Thermal resistivity is a measure of the ability of a material to resist heat transfer by conduction. It is the inverse of thermal conductivity, and is measured in units of [m.K/W]. 3.2.1.3. SPECIFIC HEAT CAPACITY Specific Heat Capacity measures the ability of a material to store heat energy. It is measured in units of [kJ/kg.K] 3.2.1.4. DENSITY Density measures the mass of a unit volume of material. It is useful to allow the calculation of heat capacity by volume. It is measured in units of [kg/m3].

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3.2.2. CONSTRUCTION PROPERTIES A material or group of materials forming a construction element of a building has properties that are determined partly by the thermal properties of the materials themselves, and partly by the surface characteristics and geometry of the construction. The properties of construction elements that are most relevant to thermal performance are as follows:

     

Overall heat transfer coefficient (U-value). Overall thermal resistance (R-value). Heat capacity. Emissivity (= absorptivity). Relectivity Transmissivity.

3.2.2.1. OVERALL HEAT TRANSFER COEFFICIENT (‘U’ VALUE) The overall heat transfer coefficient is an approximate measure that simplifies the calculation of heat transfer through walls, floors and roofs. It combines the heat transfer coefficients for convective and radiative heat transfer from both surfaces with the conductive heat transfer to provide a single overall heat transfer coefficient for the surface. It is somewhat approximate, since the surface heat transfer coefficients for both convective and radiant heat transfer are dependant on the surface temperatures. It is measured in units of [W/m2.K]. 3.2.2.2. OVERALL THERMAL RESISTANCE (‘R’ VALUE) Overall thermal resistance is the inverse of overall heat transfer coefficient, and is a measure of the resistance to heat transfer of a building element such as a wall, floor or roof. It is found by adding the individual thermal resistances of each layer of the element, including the surface resistances of the inner and outer surfaces. It is measured in units of [m2.K/W]. 3.2.2.3. HEAT CAPACITY Heat capacity is a measure of the ability of a building element to retain heat. Specific Heat Capacity measures the ability of a material to store heat energy. It is measured in units of [kJ/m3]. 3.2.2.4. COMBINED HEAT CAPACITY AND RESISTANCE It has been suggested that the combined effect of heat capacity and resistance may be an important criterion for the effectiveness of wall materials. This is defined as the product CR (heat capacity multiplied by overall thermal resistance). It is suggested by Hamilton et. al that a figure of CR=93 [x103sec] may be optimum for the climate in Botswana. It has units of seconds. 3.2.2.5. EMISSIVITY Emissivity is a measure of the ability of a surface to emit radiant heat energy, relative to that of a black surface at the same temperature. It is a dimensionless ratio between 0 and 1. It is equal to absorptivity, which is a measure of the ability of a surface to absorb radiant heat energy.

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3.2.2.6. REFLECTIVITY Reflectivity is a measure of the ability of a surface to reflect radiant energy. It is a ratio between 0 and 1. 3.2.2.7. TRANSMISSIVITY Transmissivity is a measure of the ability of a material to transmit radiant energy through it. It only applies to translucent materials such as glass. It is a ratio between 0 and 1.

Table 3.3. Values of Surface Film Resistance based on Direction of Heat Flow

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Table 3.4. Thermal Resistances Unventilated Air Layers between Surfaces with High Emittance SOLAR HEAT GAIN COEFFICIENT (SHGC) The fraction of external solar radiation that is admitted through a window or skylight, both directly transmitted, and absorbed and subsequently released inward. The solar heat gain coefficient (SHGC) has replaced the shading coefficient (SC) as the standard indicator of a window's shading ability. SHGC is expressed as a number between 0 and 0.87, SC as a number between 0 and 1; i.e., the relationship between SHGC and SC is: SHGC = SC × 0.87. The lower a window's SHCG, the less solar heat it transmits, and the greater its shading ability. SHGC may be expressed in terms of the glass alone or may refer to the entire window assembly. To reduce the SHGC, manufacturers can apply a spectrally selective low-E (low-emissivity) coating to glazing. This type of low-E coating can reduce heat loss in the winter as well as solar gain in the summer. Reflective coatings and tinted glass can also help reduce the SHGC. In passive solar design, south-facing windows with high SHGC ratings might be needed to provide a building with heat in the winter. But a properly designed roof overhang is typically used to reduce the solar heat gain from these windows in the summer. Some window coverings – shades, blinds, mesh screens, and awnings – can also be used to reduce solar heat gain in the summer or as needed.

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Figure 3.18. Direct & Indirect Solar Radiation

PROJECTION CALCULATION BASED ON SHGC

Table 3.5. SHGC ‘M’ Factor Adjustments for Overhangs and Fins

Table 3.6. Defaults for Untreated Vertical Fenestration (Over all assembly including Sash & Frame)

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3.3. ORIENTATION 3.3.1. REDUCING SOLAR HEAT GAIN IN SUMMER The main factor that determines the optimal orientation for a building is the daily path of the sun through the sky, and the pattern by which this changes through the year. The main aim is to minimize solar gain on vertical surfaces in summer. The east and west walls are exposed to the sun in the mornings and afternoons respectively, and the area of these walls should be reduced as far as possible. The optimum orientation is therefore with the longer axis of the building running east - west.

Figure 3.19. Sunpath in Summer and Winter

Figure 3.20. Using the Roof Overhang to shade the Sun in Summer

Table 3.7. Effect of orientation on energy consumption for three types of building

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3.3.2. ALLOWING SOLAR HEAT GAIN IN WINTER In buildings that require heating in winter, a further consideration is to achieve solar heat gain in the winter. The north wall may be designed to receive sunshine in winter, but not in the summer, by arranging shading devices (which may include the roof overhang), that expose the wall to the low winter sun, but shade it from the sun in the spring and autumn when heating is not needed. Buildings with high internal heat gains such as offices have very little need for heating even in winter, and in this case solar heat gain should be avoided at all times. 3.3.3. QUANTIFYING THE EFFECT OF ORIENTATION. The effect of changing orientation from E-W to N-S is simulated for three different building types – Institutional, Residential & Commercial in order to identify the building type which requires energy savings the most. The effect on energy performance in summer, winter and the full year is summarised in table 3.7. The overall effect on energy performance is significant for the classroom building (6.1% increase in annual energy consumption for heating and cooling). It was less for the residential building (2% increase in annual energy consumption for heating and cooling). It had no effect at all for the office building; a winter saving of 8.4% cancelled a summer additional cost of 5.9%. Total energy consumption is however not the only important criterion. Windows that admit direct sunshine result in internal areas that are too hot and subject to glare. An E-W orientation allows for the larger elevations of a building to face north and south. The north elevation can be more easily protected from the sun than the east and west elevations, and the south elevation is not a problem in this regard.

3.4. CHARACTERISTICS OF ENVELOPE ELEMENTS FOR ACHIEVING ENERGY EFFICIENCY The design team must find the combination of characteristics for each building element that best achieves the requirements of the design brief. This requires consideration of the particular conditions that each element is exposed to, in terms of the opportunities and threats that these offer the building. By considering the optimal characteristics of each element of the building envelope, the most appropriate combination of elements can be achieved. This requires the coordinated input of different specialists to ensure that all the disciplines involved in the building are considered. Figure 3.21. Envelope Heat Flows

3.4.1. GROUND FLOOR The average monthly temperature in India ranges between 25°C in January and 12°C in July. The ground temperature at a depth of 500mm below natural ground level is approximately equal to the average monthly temperature.

ENERGYâ&#x20AC;&#x201C;EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Buildings generally benefit from ground floors that are in good thermal contact with the ground, by losing heat to the ground. The simulation for an office building indicated an increase in annual heating and cooling energy of 22.9% when 50mm of insulation was provided between the floor and the ground, compared with no insulation.

3.4.2. ROOFS Of all the building elements, the roof is most exposed to climatic sources of heat gain and heat loss. Throughout the day the roof is exposed to direct solar radiation, which is potentially the most significant source of heat gain. The most important strategy is to manage the transfer of heat through the roof structure. For most of the year this is achieved by reducing heat transfer as much as possible. The most effective strategy is to use a reflective surface for the roof finish, such as white painted galvanised steel. This reduces the amount of heat that passes into the roof space in the first place. A similar advantage may be achieved by using a reflective underlay (such as Sisalation) under concrete tiles. Ventilation of the roof space can help to reduce the temperature further, and insulation laid over the ceiling can help to reduce the transfer of heat from the roof space into the occupied rooms below.

Figure 3.22. Sunpath in Summer and Winter

3.4.3. WALLS In designing the walls consideration should be given to the different conditions that they will be exposed at each time of day and season depending on their orientation. In some cases there are conflicting opportunities or constraints at different times of year, e.g. a west facing wall may benefit from the heat of the sun in winter, but suffer in the summer. It appears that different solutions are appropriate for different types of building. 3.4.3.1. EAST AND WEST ELEVATIONS Walls that face the east and west should generally be as well insulated as possible, to prevent summer heat gain from the low morning and evening sun. These elevations can benefit from shading from trees, shrubs or climbing plants. If these are deciduous, the building can benefit from morning and afternoon heat gain in the winter months while being protected in the summer. For buildings with large internal loads that require cooling in winter, evergreen trees or climbers would be more appropriate. 3.4.3.2. NORTH ELEVATION The north elevation receives sunshine during the winter months, with the sun at an average midday altitude of 42Â° in June. In midwinter the sun rises in the northeast and sets in the northwest. During this time, the north elevation is therefore exposed to quite large amounts of direct solar radiation that can provide some useful heat gain in this cold period for buildings such as residential houses that require heating. Buildings such as offices or classrooms that have very little need for heating should have the north walls protected from the sun if possible. The heating season typically begins in April

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and ends in August. At these times of year the midday sun reaches an altitude of about 55°. It now rises and sets about 15° north of the east – west axis so that it sees little of the north wall in the early morning and late afternoon. Shading of windows on this elevation should therefore be designed to protect the windows when the sun is above an altitude of about 60°. 3.4.3.3. SOUTH ELEVATION The south elevation receives only a glancing blow from the sun in the early morning and late afternoon in mid summer. By midday the sun is almost directly overhead. The south wall may therefore be a good opportunity to introduce thermal mass to increase the thermal capacitance of the building. This is the best elevation on which to locate windows for daylighting, since these receive little or no direct sunlight. 3.4.3.4. SIMULATION OF WALL INTERVENTIONS The simulation showed that for the residential building type substantial energy savings can be achieved by using insulated cavity walls, or insulated mass walls in place of standard 220mm walls. Increased mass walls with insulation are marginally better than insulated cavity walls, but the improvement was marginal. The benefit was almost entirely in reduced heating energy in winter. When the building requires cooling, the walls actually help by absorbing heat from the inside during the day and transferring it to the outside at night. As a result, insulated walls resulted in increased energy consumption for both the institutional and office building types, where cooling energy greatly exceeds heating energy.

Table 3.8. Effect of wall insulation on energy consumption for three building types

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3.4.4. FENESTRATION The primary objective in designing the fenestration for a building should be to maximise the benefits, namely:

      

Daylighting Views Ventilation while minimising the negative qualities Glare Radiant heat gain Conductive and convective heat gain and heat loss

3.4.4.1. DAYLIGHTING The objective of window design with respect to lighting should be to provide as much of the indoor lighting requirement with daylighting as is possible without compromising other energy efficiency considerations. In particular this will require consideration of the heat transfer properties of the glazing. This is an element that may justify some cost analysis, as there is a clear relation between cost and thermal effectiveness. Improved insulation can be achieved using various configurations of Multiple glazing, and selective coatings, the cost of which is generally more the greater the effectiveness of the product. Selective coatings may also reduce the light penetration, so that in some cases the same quantity of daylight may be achieved with smaller clear windows as with larger coated windows, with lower cost and overall heat loss.

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3.4.4.2. VIEWS Views of the outdoor environment have an important impact on the quality of the indoor environment for a variety of occupations, and can significantly improve people’s productivity. 3.4.4.3. SIMULATION OF WINDOW INTERVENTIONS Various interventions are simulated on the three types of buildings, including shading of north facing windows, double glazing, increasing the glazing ratio, and using specialised glass. Double glazing is found to have very little effect on energy consumption, with an annual savings as follows:

  

Residential 3.6% Classroom 0.3% Office 0.0%

North window shading has some benefit for classrooms and office buildings, but not for the residential building, with annual energy savings as follows:

  

Residential -0.3% (increase in energy) Classroom 4.8% Office 6.0%

Increasing the glazing area from 20% to 40% of external wall area resulted in substantial increases in energy consumption for all building types. This was somewhat mitigated by using ‘Coolvue’ glass with a selective coating, but overall energy consumption was still between 10% and 30% higher than in the base case. It is recommended that glazing areas are generally kept to no more than about 30% of external wall area. Higher glazing levels in air conditioned buildings will lead to excessive consumption of energy unless sophisticated design measures such as ventilated double facades or solar control glass with external shading are employed. In buildings that are not air-conditioned, large amounts of glazing will result in high indoor temperatures and uncomfortable buildings.

Table 3.9. Effect of glazing interventions on energy consumption for three building types

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

CHAPTER 4

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

4.1. INTRODUCTION Performance Assessment of Office Buildings is necessary to achieve an energy efficiency level of greater than 50% toward a net zero building from ASHRAE/IESNA Standard 90.1-2004 (ASHRAE 2004). No single discipline alone can apply sufficient measures to achieve this level of energy efficiency. The burden must be shared, and a holistic approach must be understood. Hence the focus of this chapter is on technical multidisciplinary strategies to achieve significant energy savings in Building Envelope Design of Office Buildings including operational performance, occupant comfort, and indoor environmental quality and the analyses clearly show that systematically applied multidisciplinary approaches are essential to achieve the 50% energy savings. This chapter includes the following guidance:

   

Overview of design influences Building and site design features Energy conservation measures (ECMs) Multidisciplinary coordination for energy efficiency

Figure 4.1 shows the relative contribution of energy savings associated with each large scale design component to build up to a 50% energy reduction over the ASHRAE/IESNA Standard 90.1-2004 baseline building. Within the heating, ventilating, and air-conditioning (HVAC) and lighting components reside key architectural decisions associated with the configuration of the façade. It should be noted that it was not possible in any of the energy modeling runs to Figure 4.1. Comparison of Baseline to Prescriptive 50% AEDG achieve the 50% energy savings by Solution Showing Breakdown of Energy Savings Components looking at mechanical and lighting equipment optimization alone. Therefore, the performance of the envelope and its impact on loads and lighting become essential to reaching the energy use intensity (EUI) budget goal.

2.7. OVERVIEW OF DESIGN INFLUENCES There are many design decisions that influence the energy use of a building (as expressed in kBtu/ft2/yr). The energy use of an office building is driven primarily by choices related to envelope, lighting and HVAC systems. The first and foremost area of design control is the building envelope, which involves the selection of building insulation and glazing to reduce heat transfer through surfaces, thereby reducing conduction and solar gains while enhancing daylighting opportunities. As noted in Figure 4.2, decisions about key elements of the building envelope are interrelated and heavily influence the heating and cooling strategies. It should be noted that while internal heat gains are all additive (i.e., cause the need for cooling), gains related to interaction with the outdoor climate, such as ventilation and building envelope, can be either heat gains or losses and are therefore heavily dependent on climate zone.

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Figure 4.2. Heating and Cooling Influences on Building Envelope Design

2.8. BUILDING & SITE DESIGN FEATURES There are many building architectural design features that impact the energy performance of a building. The major features include the building location (climate), shape, size, number of stories, and orientation. Each of these are presented in detail in this section.

4.3.1. CLIMATE FEATURES CLIMATE CHARACTERIZATIONS BY LOCATION There are several major climatic variables that impact the energy performance of buildings, including temperature, wind, solar energy, and moisture. These variables continuously change and can be characterized by annual or seasonal metrics. In combination, these variables show that distinct patterns emerge with regard to climate types, each of which has particular energy impacts on building design and operation. India has been divided into five primary climate zones (Hot & Dry, Warm & Humid, Temperate, Cold and Composite) for the specification of design criteria in the major energy codes such as Energy Conservation & Building Code. The characterization of these climate zones is based on seasonal performance metrics, not on the peak or design values. No single design strategy applies to all of these climate combinations. Each set of climate combinations needs to be analyzed separately. It is important for the design team to determine the particular unique characteristics of the climate closest to the site. Annual hourly climate data is usually used for energy modeling and is available from federal government sources. In addition to the acquisition of local data, it is necessary to assess any local topography or adjacent properties that would cause reduction in access to sunlight and passive solar heating.

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CLIMATE INFLUENCES It is not reasonable to present every design strategy for each climate, but there are some fundamental principles that apply. The sensible and latent loads due to people are universal across all climate zones since the occupant densities and hours of occupation are assumed to be climate independent. Typically, the lighting power levels are the same but the energy use changes with location due to the daylighting available. While there are benefits to the use of renewable energies (photovoltaics, solar, wind), these technologies are not design strategies that are required to achieve 50% energy savings.

4.3.2. BUILDING FEATURES BUILDING SHAPE The basic shape of the building has a fundamental impact on the daylighting potential, energy transfer characteristics, and overall energy usage of a building. Building plans that are circular, square, or rectangular result in more compact building forms. These buildings tend to have deep floor plates that limit the potential of sidelighting a significant percentage of occupiable space. Building plans that resemble letters of the alphabet, such as H, L, and U, or that have protruding sections and surfaces at angles other than ninety degrees relative to adjacent building surfaces tend to have shallow floor plates where sidelighting strategies result in a higher percentage of daylighted floor area. (Atriums and other core lighting strategies may also be introduced into more compact building forms to achieve a similar effect.) Less compact forms increase a building’s daylighting potential, but they also may magnify the influence of outdoor climate fluctuations. Greater surface-to-volume ratios increase conductive and convective heat transfer through the building envelope. Therefore, it is critical to assess the daylighting characteristics of the building form in combination with the heat transfer characteristics of the building envelope in order to optimize overall building energy performance. The shape of the building also defines the window area and orientations that are available. Windows allow solar gains to enter the building; this is beneficial during the heating season but increases the cooling energy. The building shape needs to be designed so that the solar loading is properly managed. The solar management strategy changes by local climate characteristics, as solar intensity and cloudiness differ. Additionally, the shape of the building determines how wind impinges on the outdoor surfaces to assist natural ventilation or creates outdoor microclimates. In addition, attention must be paid to the effect of wind passing through openings in the façade (e.g., windows, louvers, trickle vents, cracks), as this can drive unforeseen and/or uncontrollable infiltration. BUILDING SIZE The size of the building impacts the energy use. Analysis of a small 20,000 ft2 two-story office building and a medium 53,600 ft2 three-story office building clearly demonstrates the differences. Figure 4.3 presents the baseline site energy use intensities for these two buildings for compliance with ASHRAE/IESNA Standard 90.1-2004 (ASHRAE 2004). The size of the building also impacts the Energy use. In these cases, there are limited options for obtaining more energy-efficient Building Envelope. Building size and especially depth of floor plate can have significant impacts on the feasibility of daylighting and natural ventilation.

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Figure 4.3. Energy Saving For Small & Medium Office Buildings

NUMBER OF STORIES Typically, as the number of stories of a building increases, some aspects of design become more complicated. For instance, requirements for structural performance and durability/design life may affect choice of envelope components, the viability of exposed thermal mass, and the amount of area that may be used for fenestration. All of these may affect energy performance. Taller buildings will have elevators with significant horsepower motors but intermittent energy use. Tall buildings run the risk of trapping a large block of space as purely internal and without connection to the outdoors. If an increased amount of space with access to natural daylight or ventilation is preferred, the designer of taller buildings can introduce toplight using skylights, clerestories, monitors, sawtooths, and atriums. Horizontal glazing captures high-angle sun and may be difficult to shade. Exterior louvers, translucent glazing, vertical glazing, and other means should be considered to distribute toplight evenly into an interior space. BUILDING ORIENTATION The orientation of the office building has a direct impact on the energy performance primarily due to the orientation of the fenestration. The annual solar radiation impinging on a surface varies by the orientation and latitude, as shown in Figure 4.4. The north solar flux (south solar flux for the southern hemisphere) is the least for any location; however, north daylighting is preferred due to no glare control requirements from direct sun penetration (reflections from adjacent buildings may require blinds on north windows for glare control). The east and west are essentially the same. The west exposure needs to be critically evaluated since it contributes to the peak or design cooling load. South-facing orientations in the northern hemisphere have the second largest solar intensity and the greatest variation in sun angle. Great care must be applied when designing external shading for this orientation, as attention must be paid to heat gain, glare, and the possibility of passive solar heating in cold climates. The horizontal solar flux is the largest and is critical if flat skylights on the roof are being considered. Clerestories on the roof facing north would be a preferred option.

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Figure 4.4. Annual Solar Radiation by Orientation for Office Buildings

Permanent projections can contribute to reducing the solar gains. Solar heat gain coefficient (SHGC) multipliers for permanent projections are presented in Figure 4.5. The largest energy reductions are on the south, east, and west orientations. Building orientation and the placement of fenestration can have a significant effect on the ability of a design to provide useful daylight to perimeter zones. Using caution when doing simultaneous building configuration studies and internal space planning can maximize the amount of normally occupied space that can use daylighting for ambient light. For example, place all open office spaces on the north and south sides of the building where daylight is most easily managed.

Figure 4.5. SHGC Multipliers for Permanent Projections

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BUILDING OCCUPANCY TYPES Building function and occupancy type are key drivers for all internal heat loads. The density of the occupancy leads to heat from bodies, heat from equipment/computers, and heat from the electric lighting that runs in order to make the environment habitable. Some typical internal heat loads for office buildings are shown in Table 4.1.

Table 4.1. Typical Internal Heat Gains for Office Spaces

In addition to internal loads, other key occupancy-based criteria include the provision of sufficient ventilation to ensure indoor air quality (IAQ). It is never the intent to achieve energy efficiency at the cost of human health. Additionally, depending on the function of work in the space, there may be acoustic design Requirements. Specific recommendations for lighting levels and visual contrast at and surrounding the work surface can be found in the next chapter.

2.9. ENERGY CONSERVATION MEASURES (ECMs) The major ECMs focus on the envelope design and lighting considerations. This section of this chapter looks at each of these components to understand the relative design influence on total EUI. The place to start is understanding where the baseline and business-as-usual buildings would start in terms of energy savings. An energy model can reveal the relative proportion of energy savings contributed by each of the above mentioned design components. In general, most energy modeling programs output end-use data instead of linking the relative influence of design decisions directly to the output. Figure 4.6 shows a classic output that has all envelope and building configuration design decisions embedded in and diluted by total cooling, heating, interior lighting, exterior lighting, and HVAC system fan components. Clearly the heating and cooling energy savings vary significantly by location, so each requires particular attention specific to the climate. However, the energy savings from interior lighting, exterior lighting, interior equipment, and fans each contribute almost equally to the total energy savings, which means that these four major components all have to be addressed in every location. The second key step to reducing energy use is to apply a series of ECMs, as noted in this Guide. Figure 4.6 shows an example of how one might use iterative energy modeling in a simplified approach to map the relative contributions toward energy savings achieved by each collective design decision made by the team.

4.4.1. ENVELOPE The envelope is characterized by the opaque components and fenestration. Improvements should be considered for reduced thermal transmittance (i.e., U-factors), use of thermal mass, and control of solar heat gains. Upgrades to the opaque elements such as the roofs/ceilings (flat or sloped), walls (lightweight or mass), and foundations (slabs, crawlspaces, and basements) include increased

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

insulation to lower thermal transmittance values (i.e., U-factors) or more thermal mass for roofs and walls. Adding cool roofs with high reflectivity in climates with more intense solar radiation is often found to be a direct benefit to reducing energy associated with cooling during the summer months. The term thermal mass refers to the building’s thermal capacitance, the amount of heat that is required to raise or lower the building temperature by a fixed amount. Greater thermal mass tends to reduce building peak conditioning loads by spreading these loads over an extended time span. Building thermal mass can reduce total conditioning loads if, across the daily cycle, exterior temperature conditions are both above and below the desired interior temperatures. Building thermal mass, furthermore, can absorb solar heat gain with reduced temperature rise and store that heat for later use for space heating after sunset. Similarly, during periods of lower humidity and low overnight temperatures, overnight ventilation with outdoor air (OA) can be used to cool a thermally massive building, offsetting subsequent daytime sensible cooling loads.

Figure 4.6. Relative Impact of Energy Savings Strategies

The fenestration has a major impact on both the architectural appearance and the energy savings potential. In addition, glazing provides daylighting and views for the occupants, connecting them to the outside world and improving occupant comfort and productivity. Considerable effort needs to be focused on the fenestration designs to ensure the proper balance among heating, cooling, and daylighting is achieved. While electrical lighting energy can be saved through daylight harvesting, the other benefits of windows must be qualitatively weighed against the energy and cost-benefit analysis of increased HVAC energy usage due to larger window area or increased SHGC if implemented to improve access to daylight. Orientation-sensitive window-to-wall ratios (WWRs) are recommended to help control solar heat gains while allowing more visible light at orientations where solar heat gains are not as much of an issue. Careful attention should also be paid to the issue of glare, a visual discomfort usually caused by the difference in relative brightness between a computer screen and a nearby window in direct low-to-medium-angle sun. Use of exterior shading such as overhangs on the south façade can also help control solar heat gains.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Other envelope design features to consider include the use of vestibules in order to reduce the introduction of OA through uncontrolled door usage. Additionally, placement and integrity of continuous air and vapor retarders is key to preventing the uncontrolled formation of condensation within the wall cavities, a situation that can lead to increased energy use to keep materials dry enough to reduce the risk of microbial growth and/or sick building syndrome. It is strongly recommended that a façade consultant, or person with similar expertise, be involved in detailing vapor retarder placement in low-energy buildings specifically because there will be less HVAC capacity available in base building systems to accommodate for a poor wall cavity construction. Careful façade detailing for sealing, especially at joints and fenestration interfaces, will also help reduce the amount of air leakage and infiltration experienced in the building — another potentially uncontrollable, continuous, real-time load on the HVAC system that can be mitigated with minimal amounts attention during the design and construction process. In summary, the following approaches are often beneficial :

        

Enhanced building opaque envelope insulation for exterior walls and roofs Use of mass in opaque envelope insulation to reduce cooling Inclusion of a cool roof in selected cooling-dominant climates with high solar intensity High-performance window glazing Exterior shading on south-facing windows Limited window areas at east and west Limited use of flat-roof skylights; consider north-facing clerestories/monitors Vestibules at openings to the outdoors Use of a continuous air barrier to reduce condensation risk and infiltration

4.4.2. LIGHTING The lighting system is composed of three elements: daylighting, interior lighting, and exterior lighting. Daylighting can save electric lighting energy if there is a sufficient level of daylight available to meet interior illuminance requirements and if controls are employed to reduce the electric lighting in response to the available daylight. Interior lighting is a major energy user of the building and is constant across all climate zones; however, local site characteristics such as frequency of cloudy days or shading cast by adjacent properties will cause significant differences in overall interior energy use when daylighting is used. Equipment used and fixture energy density associated with exterior lighting are also consistent across all climate zones. It should be noted that energy use across climate zones with regard to annualized nighttime hours is constant; however, local site characteristics, such as which lighting zone (LZ) the building is located in, will cause differences in site energy use. Exterior LZs are a recognition of the types of surrounding buildings and are discussed later in this chapter in more detail.

4.4.2.1.

DAYLIGHTING

Providing daylight is fundamental for an office environment, as it makes a key contribution to an energy-efficient and eco-friendly office environment. While the most valuable asset of daylight is its free availability, the most difficult aspect is its controllability, as daylight changes during the course of the day. Daylighting is more of an art than a science, and it offers a broad range of technologies that provide glare-free balanced light, sufficient lighting levels, and good visual comfort. Daylighting strategies drive building shape and form, integrating them well into the design from structural, mechanical, electrical, and architectural standpoints.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Daylighting increases energy performance and impacts building size and costs by downsizing fans, ductwork, and cooling equipment because overall cooling loads are reduced, allowing for tradeoffs between the efforts made for daylighting and the sizing of the air-handling and cooling systems. Daylighting will only translate into savings when electrical lighting is dimmed or turned off and is replaced with natural daylight. Effective daylighting uses natural light to offset electrical lighting loads. When designed correctly, daylighting lowers energy consumption and reduces operating and investment costs by

    

reducing electricity use for lighting and peak electrical demand, reducing cooling energy and peak cooling loads, reducing fan energy and fan loads, reducing maintenance costs associated with lamp replacement, and reducing HVAC equipment and building size and cost.

However, to achieve this reduced cooling, the following criteria must be met:

  

High-performance glazing is used to meet lighting design criteria and block solar radiation. Effective shading devices, sized to minimize solar radiation during peak cooling times, are used. Electric lights are automatically dimmed or turned off through the use of photosensors.

The case for daylighting reaches far beyond energy performance alone. Indoor environmental quality benefits the office workers’ physical and mental health and has a significant impact on their performance and productivity. These impacts are difficult to quantify, but the potential for improvement and economical savings is immense and needs to be taken into consideration as serious decision-making criteria in the process of office design. These benefits may far outweigh the energy savings and become the significant drivers for daylighting buildings altogether. The daylighting strategies recommended in this Guide have successfully been implemented in buildings. Most daylighting strategies are generic and apply to office buildings just as they do to other building types.

4.4.2.2.

INTERIOR LIGHTING

The primary lighting goals for office lighting are to optimize the open office spaces for daylight integration and to provide appropriate lighting levels in the private and open office spaces while not producing a dull environment. Producing a vibrant lighting environment is extremely important when attempting to minimize energy use, especially in the building’s common areas (lobby, corridors, break rooms, and conference rooms). To achieve maximum lighting energy savings, lighting power densities (LPDs) need to be reduced and most spaces need to be provided with occupancy sensors and/or daylight-responsive dimming to reduce or shut off the lights when they are not needed. Additionally, the “night lighting,” lighting left on 24 hours to provide emergency egress, needs to be designed to limit the power to 10% of the total LPD. The interior space types typically found in office buildings are displayed in Table 4.2, along with the ASHRAE/IESNA Standard 90.1-2004 (ASHRAE 2004) percentage assumptions developed by PNNL. Each building space distribution will most likely be different, which creates different opportunities for energy savings. The building may have more than the standard 15% open office area, which creates more opportunities for daylighting, or the building may have more than the 29% private office area, which creates greater savings from occupancy sensors.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

The first opportunity for energy savings is the reduction of the LPDs from those listed in the “Standard Baseline LPD” column in Table 4.2. Simple reductions are possible by using high-performance T8 lamps and premium low-ballast-factor (0.77) ballasts. This will reduce the T8 wattage by approximately 20% over the Standard 90.1-2004 LPD calculations. Additional LPD savings are possible by using advanced luminaires such as the new twolamp T8 or T5 high-performance lensed luminaires instead of prismatic lensed, parabolic, or recessed basket fixtures.

Table 4.2. Standard Percentage Assumptions by Space Type

Ensuring that lights are on only when someone is using them is an important opportunity as well. In Standard 90.1-2004 there are minimal requirements for occupancy controls. By adding manual ON or auto ON to 50% occupancy sensors to open office task lighting, general lighting in private offices, conference rooms, storage, and lounge/recreation spaces and auto ON occupancy sensors to electrical/mechanical rooms and restrooms, the lighting system will use 15% to 20% less lighting energy.

4.4.2.3.

EXTERIOR LIGHTING

Exterior lighting energy savings are accomplished by reducing the LPD and using automatic controls. Further savings are available by turning off façade lighting and reducing parking lighting by 50% between midnight and 6:00 a.m. The new exterior LPD allowances in ASHRAE/IES Standard 90.1-2010 classify buildings in a five-zone lighting system (see Table 4.3). Very few buildings covered here are located in LZ4, which requires LPDs that are equivalent to those in Standard 90.1-2004. Most of the buildings addressed here will be located in LZ3, which requires approximately 35% less energy than LZ4. This 35% energy savings includes reducing the façade lighting allowance by 50%. Some smaller office buildings may be classified into exterior LZ2, which will reduce exterior lighting loads by approximately 50% over LZ4.

Table 4.3. Exterior Lighting Zones

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

4.4.3. QUALITY ASSURANCE Quality and performance are the result of intention, sincere effort, intelligent direction, and skilled execution. A high-quality building that functions in accordance with its design intent, and thus meets the performance goals established for it, requires that quality assurance (QA) be an integral part of the design and construction process as well as the continued operation of the facility. Deficiencies in the building envelope have a wide range of consequences, including elevated energy use or underperformance of the energy efficiency strategies. These deficiencies are commonly a result of design flaws, construction defects, malfunctioning equipment, or deferred maintenance. The QA process typically referred to as commissioning (Cx) can detect and remedy these types of deficiencies. As facilities search for higher efficiency through innovation, new applications, and complex controls, the risk of underperformance and the potential for more deficiencies increases. To reduce project risk, Cx requires a dedicated person (one with no other project responsibilities) who can execute a systematic process that verifies that the systems and assemblies perform as required. The individual responsible to provide this is called the commissioning authority (CxA). Success of the Cx process requires leadership and oversight. CxA qualifications should include an indepth knowledge of mechanical and electrical systems design and operation as well as general construction experience. The individual represents the owner’s interests in helping the team deliver a successful building project. The CxA can be completely independent from the project team companies or a capable member of the contractor, architect, or engineering firms. The level of independence is a decision that the owner needs to make. The Cx process defined by ASHRAE Guideline 0, The Commissioning Process (ASHRAE 2005), and ASHRAE Guideline 1.1 is applicable to all office buildings. Owners, occupants, and the delivery team benefit equally from the QA process. Large and complex buildings require a correspondingly greater level of effort than that required for small, simpler buildings.

2.10. MULTIDISCIPLINARY COORDINATION FOR ENERGY EFFICIENCY 4.5.1. MULTIDISCIPLINARY RECOMMENDATIONS 4.5.1.1. DEFINE BUSINESS AS USUAL BASELINE BUILDINGS One of the very first things that the design team must define is what the “business as usual” (BAU) design solution would be. This will often be a minimally prescriptive ASHRAE/IES Standard 90.1 equivalent consisting of a square or rectangular building virtually filling the site with as low a profile as possible. The energy use of this building typically represents the high-end of allowable energy use and sets the comparative standard against which absolute savings are achieved on the road toward net zero energy use. The comparison to the BAU benchmark is a real measure of success reflective of all design decisions. The second key item that the design team must define is what the baseline design solution would be once the preferred building configuration’s design is completed. The baseline is very different from the BAU benchmark because the current ASHRAE/IES Standard 90.1 requires all proposed and

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

baseline energy models to have identical shapes, footprints, and occupancies. Thus, the baseline does not reward fundamental building configuration decisions for their positive effect on energy use. It is important for the design team to agree to move away from both the BAU benchmark and the baseline in making proactive design decisions. It is also important that there is no shifting benchmark of success. 4.5.1.2. BENCHMARKING While the BAU benchmark represents the highest allowable energy-use intensity on site by calculation methods, there are a series of other energy-use benchmarks that represent the existing building stock in the United States:



U.S. Environmental Protection Agency and U.S. Department of Energy’s ENERGY STAR Portfolio Manager (EPA 2011)



U.S. Energy Information Administration’s Commercial Buildings Energy Consumption Survey (CBECS) (EIA 2011)



California Energy Commission’s California Commercial End-Use Survey (CEUS) (CEC 2008)

It is possible to benchmark the proposed design against the BAU benchmark and against its preexisting peers to demonstrate that substantial steps have been taken toward energy-use reduction. Designers often successfully compare their designs to the typical equivalent building in the preexisting stock or to the number of houses that could be powered on the energy savings to make it easier for laypeople to understand the magnitude of the energy savings. Historic data, however, is not the inspiration for good design in the future. This is where more aspirational benchmarking can benefit the team. The most frequently used benchmarks are the following:



Energy savings as designated by percentage annual cost savings as compared to Appendix G of ASHRAE/IES Standard 90.1 (ASHRAE 2010b) (typically used by codes and policies, also used by the Leadership in Energy and Environmental Design [LEED] Green Building Rating System [USGBC 2011])



Absolute EUI definitions (occasionally used by campuses, regularly used by the General Services Administration; easiest to measure and verify after construction)



Net zero energy definitions

As noted above, it is important for the design team to agree to move away from the design practices that led to older poor-performing buildings and toward a quantifiable target that is consistent with the available funding for the job. 4.5.1.3. BUDGET SHARING One oft-heard but fundamentally unnecessary question is “whose budget pays for improved energy efficiency?” The answer should always be “the owner’s budget!” When a team commits itself to delivering low-energy, holistic solutions, it is virtually impossible to discretize for the accountants how much energy efficiency each trade or discipline “purchased” on behalf of the project through its respective design decisions. A classic example is the cost of shading: there are increased structural and façade costs, but these may be offset by reduced capital cost for window glazing and air conditioning. These trade-offs are absolutely necessary to explore in consideration of the particular

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

goals and context of the building. So long as the overall building construction budget remains consistent with the Owner’s Project Requirements (OPR), it doesn’t matter where the money was spent if the whole building performs. What this tells us, however, is that discipline-based construction budget allocations might be inappropriate for the integrated design paradigm and should be reviewed early in the project. Similarly, it might be argued that traditional fee percentages may also be unintentionally preventing the disciplines most capable of proposing and proving energy-reduction techniques from applying their analytical technologies and abilities to the solutions. Lastly, the EUI “budget” itself must also be equitably shared. The building envelope does not consume energy but significantly affects the energy use of mechanical and lighting systems. Legislation and ingenuity have brought us to the point at which most electrical, mechanical, and lighting equipment has been optimized for the current state of technology. Therefore, it is important for design teams to carefully review the relative proportion of energy use by discretionary design choice and collectively attack those portions of the pie chart that represent the greediest users. A classic example is the use of all-glass façades with the expectation that highly efficient HVAC systems will somehow accommodate the egregious gesture; thankfully, energy codes are now biased to avoid this practice. Another more subtle example is the issue of plug loads in highly efficient buildings. As the intentional reduction of lighting and mechanical energy use is applied, the plug loads grow in a relative manner to upwards of 50%. This should immediately tell all parties that plug loads need to be addressed, either with automatic shutdown controls or with substantial reduction in required, desired, or assumed load on the part of the owner and design team. If the team knows that it is accountable for sharing the responsibility for the end energy-use burden, it sets the tone for sharing the energy-savings burden as well.

4.5.1.4. INVESTMENT FINANCIAL ANALYSIS Many of the examples thus far have discussed trade-offs made by the design team to reduce the total building energy use. In order to confirm that each decision contributes to affordable energy savings, energy modeling can be coupled with a series of financial analyses to show which ECMs give “the biggest bang for the buck.” The three most typical tools include the following:



Life-Cycle Cost Analysis (LCCA) is a calculation method that adds first cost to 20–25 years of annual energy and maintenance costs, inclusive of equipment replacement costs and an estimate on inflation. The option that has the lowest life-cycle cost is usually chosen if the budget allows. LCCA is the financial tool most often used by institutional owners planning to hold and operate the building through a few generations of equipment technology.



Simple Payback Period is a calculation method that divides first cost by the annual energy savings to determine how long it will take to break even on the investment. The simple payback is most often used by developers looking to recoup costs before divesting of a property or by long-term building owners with limited funding for retrofits.



Return on Investment (ROI) is a calculation that takes the ratio of the energy savings over a predefined number of years minus the first costs divided by the first costs. It essentially answers the question “what is my rate of return on the investment?” and allows a somewhat parallel comparison to the rate of return used in the financial markets. The ROI method is usually used by wealth-holding clients comparing relative opportunity costs when looking to invest in stable profit

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

growth. In downturn economies burdened with the ever-rising cost of energy throughout the world, some financial institutions have begun to provide financing for energy-efficiency upgrades based on projected ROI through vehicles based on ROI calculations. It is important in all of these financial comparisons that the team agree on which inflation and depreciation rates are appropriate for use.

4.5.1.5. BUILDING CONFIGURATION AND FLOOR AREA MINIMIZATION In the area of building design, the first item to address is the built area. For first-cost reasons, there is obviously a drive toward the minimization of built square footage, and the entire team should review the actual requested occupancies to determine if space can be shared as flexible space between uses otherwise listed separately. For instance, shared conference spaces or lounge spaces can reduce the redundancy of built space while also encouraging interdepartmental synergy. Another area often under scrutiny for cost savings (both first cost and operating costs) is the transient gross square footage associated with circulation space and lobbies. It is recommended that the team use space-planning exercises to review if there are ways for these types of spaces to be reduced in size through merging with other functions or to be limited in scope and controllability with regards to expenditure of energy under low-occupancy conditions. The second major item for the team to address is the architectural configuration of the building. Facade square footage represents a source of conductive heat loss or heat gain as the OA temperatures fluctuate; therefore, the larger the amount of façade area, the greater this impact. Additionally, most façades for office buildings contain windows for the benefit of the occupants. Glazing is a poorer insulator than most opaque constructions and should be reviewed with regard to its placement and size. Generally speaking, daylighting and natural ventilation are possible within about 25 ft of a façade, a value that may govern the depth of footprints aspiring to greater connectivity to the outdoors. Beyond the impact on the interior floor plate, the shape of the building also informs where and how the building self-shades and begins to inform where glazing can be most effectively placed. Generally speaking, in the northern hemisphere, glazing that points toward the north captures sky reflected daylight with minimal solar heat content, making it the ideal source of even light. Eastern and western glazing is impacted by low-angle sun throughout the year, which can cause glare and thermal discomfort if not mitigated properly. Lastly, in the northern hemisphere, southern façades with glazing benefit from overhangs to reduce solar load during the summer season.

4.5.1.6. SCHEDULES OF OCCUPANCY, USE, AND UTILITY RATES It is essential that the team understand the schedules related to utility rates, especially any embedded demand charges and on/off/hi/low/seasonal peak period definitions local to the site and its service utility. This is because the prevailing benchmarks for energy savings in ASHRAE/IES Standard 90.1 and most energy codes are based on annual cost, not absolute energy savings. Most importantly, the owner pays for the demand and consumption charges. This means that discretionary decisions by the team to avoid onerous demand charges through load shifting may be appropriate when looking to reduce annual operating expenditures. It is important for the team to map out the anticipated schedules of use and occupancy for each area of the building. This is information that is crucial to the energy modeling and can greatly affect

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

the outcomes with regard to estimated energy savings over a known benchmark or LCCA. It is important to note that most energy models run the same schedule week after week, so schedules not only should be configured to cover typical weeks but also should be changed to account for any known long periods of building closure. It is important also to look at how the relative schedules interact with each other. For instance, the following assumptions and techniques are often used in energy modeling in the office context:



Lighting schedules in areas with occupancy sensors are often arranged to have 100% light for any nonzero level of occupancy.



Small power loads representing office equipment are often arranged to have a percentage load to match the percentage of occupants, except for a 10%–15% nighttime parasitic load for equipment in sleep mode or that is not automatically turned off.



KITCHEN/LOUNGE/VENDING EQUIPMENT—this equipment tends to have high usage during the midday hours. It is important to examine the schedule of operation of such equipment as microwaves and heating plates as well as the operation of any exhaust fan associated with odor control in the area. Refrigerated vending machines and refrigerator/freezers tend to operate throughout the day to cycle to maintain internal conditions. It should be noted that newer vending machines have occupancy sensors that trip on the display lighting for the patron but then revert to a darkened mode.



CONFERENCE FACILITIES—engineers must make a judgment in energy modeling as to whether or not the conference facilities should be modeled as independent zones with an occupancy schedule. The reason for this is that there are different ways of thought about these areas. Some argue that the people in the conference room are the same as the people who would have been in the adjacent offices, so one should just have a large zone inclusive of the conference and office areas, with the appropriate diversity applied during load calculations but not during energy modeling. Other engineers argue that set-aside conference rooms do have an increased instantaneous occupancy that can drive up overall ventilation rates in systems serving both conference rooms and offices, so the true model should reflect the increased load. The problem with the latter approach is that the occupancy of the conference rooms will begin to form a base load every hour of every weekday for every week in the energy model.

It is necessary to review the impact of this purely modeling decision on the projected energy use of the whole building, especially if there are a large proportion of conference facilities. The last item to bear in mind regarding scheduling is whether a standardized schedule will be imposed on the energy model through regulatory requirements.

4.5.2. FACADE ZONE OPTIMIZATION One key area of focus for the multidisciplinary team is the façade zone, the nexus of many design desires. The façade must perform multiple functions simultaneously to create an adequate space for the occupants inside. The drivers for this include the following:

  

Presenting the public “face” of the building Protecting the indoors from wind and rain Sealing the building envelope to contain conditioned space

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

 

Creating a security barrier

      

Mitigating solar heat to be removed by a comfort-conditioning system

Creating a healthy and comfortable environment for occupants (thermal, acoustic, visual, and IAQ) Tempering the influence of cold and hot temperatures outdoors Controlling noise break-in from the outdoors Manipulating or enhancing daylight for useful purpose Providing views to the outdoors to improve occupant satisfaction Moving air in and out of the building (operable elements or louvers) Maximizing usable/leasable square footage indoors

The design of façades and the perimeter zone immediately behind them is particularly difficult precisely because there are competing priorities that must all be resolved in order to deliver a functioning building. Having the entire team acknowledge the full range of needs is the first step, and then they can look for integrated solutions together given a limited façade budget. In addition to the competing design needs, current technology in façade materials also creates “forced marriages” that must also be managed. For instance, very transparent glazing also usually comes with a high solar heat gain—the U-factor, SHGC, and visible transmittance (VT) come directly out of glazing selection. Table 4.2 documents some of the key points of contention that have impacts on energy efficiency of the perimeter zones and relates them to the drivers detailed in the list above.

Table 4.2. Guidance for Improving Energy Efficiency in Building Envelope Design

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Table 4.2. Guidance for Improving Energy Efficiency in Building Envelope Design (continued)

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Table 4.2. Guidance for Improving Energy Efficiency in Building Envelope Design (continued)

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

4.5.3. PERFORMANCE ASSESSMENT TO PROMOTE HEALTH AND COMFORT Near the start of a project, the design team should engage in a serious discussion of occupant health and comfort in order to define the criteria to be applied to the project. This discussion should cover the following aspects. 4.5.3.1. INDOOR AIR QUALITY (IAQ) IAQ is an essential aspect to be discussed at the start of the project in order to reduce health risks for future occupants. Good IAQ must always be a priority when considering all design decisions and must not be adversely affected when striving for energy reduction. It should be acknowledged that IAQ encompasses far more than just ventilation. The following key objectives must be taken into account in order to achieve the required Indoor Air Quality by the IPD team:

       

Manage the design and construction process to achieve good IAQ Control moisture in building assemblies Limit entry of outdoor contaminants Control moisture and contaminants related to mechanical systems Limit contaminants from indoor sources Capture and exhaust contaminants from building equipment and activities Reduce contaminant concentrations through ventilation, filtration, and air cleaning Apply more advanced ventilation approaches

Care and judgment must be applied at all stages of the process to ensure a healthy environment for indoor occupants. For more information on IAQ, refer to Indoor Air Quality Guide and its specific recommendations. 4.5.3.2. THERMAL COMFORT The design team discussion should begin by determining the normal activity level of the occupants in each main zone and the range of mandatory or voluntary dress code will be allowed in the building. The conversation should then cover the main concepts of dry-bulb temperature, relative humidity and operative/“effective comfort” temperature. What range of operative temperatures will be considered “comfortable” for the various spaces and whether this collection of comfort temperatures may vary in response to seasonal changes should be agreed upon. If possible, surveying existing tenant staff members at a similar facility to benchmark attitudes regarding thermal comfort can be beneficial. Once the criteria are set, then it is possible to produce a simplified overview of the relative effects of convective and radiative heat transfer, the reduction of evaporative and respiratory heat rejection that occurs with increased humidity, and the use of increased air movement to improve convective heat transfer in a “wind-on-skin” compensation for higher setpoints for room temperature. Clothing plays a major part in reducing energy usage. Dressing in layers allows an individual to respond to a changing interior environment. For example, in zones facing the equator (south in the northern hemisphere), the low sun angle significantly increases the penetration of direct sunlight into the building. The perceived temperature can change significantly throughout the day due to direct sunlight falling on occupants. Similarly, radiant temperature also can play a significant part in comfort, particularly in the area of asymmetry. Typical considerations for thermal comfort include :

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

     

metabolic rate, clothing insulation, air temperature, radiant temperature, air speed, and humidity.

Lastly, all parties should consider allowing a wide dead band for occupied-mode setpoints as a measure to reduce energy use (as compared to the minimum dead-band range stated in energy codes); however, these expanded temperature ranges should not be so extreme as to compromise the productivity in the work space.

4.5.3.3. VISUAL COMFORT Lighting, both daylight and electric light if designed and integrated properly, will minimize visual comfort issues in the space. Electric lighting levels should be designed to meet IES recommended light levels (IES 2011). Providing light levels that are too high or too low will cause eye strain and loss of productivity. Direct sun penetration should be minimized in work areas because the light level in the direct sun can reach 1000 or more footcandles (versus 30 to 50 footcandles from electric lighting). This high contrast ratio will cause discomfort issues. Using light shelves on the south side of the building will minimize the direct sun penetration for workers near windows while allowing daylight to penetrate deep into the building. Worker orientation to windows is also very important in minimizing discomfort issues. Computer screens should never be positioned facing windows (with workers’ backs to the windows) or facing directly away from the window (with workers facing out the windows). Both of these situations produce very high contrast ratios, which cause eye strain. Locate the computer screen and worker facing perpendicular to the window to minimize worker discomfort. 4.5.3.4. ACOUSTIC COMFORT The design team discussions should cover ambient noise criteria for each space, acoustic privacy, occupant-created background noise, and speech intelligibility. Because this Guide covers primarily design decisions related to energy efficiency, the primary topic of focus regarding acoustic comfort is noise criteria, as lower noise in the space may require the application of duct silencers, which tend to increase the friction experienced by the system and thus increase energy use. Noise criteria in the space may also require acoustic ceilings and carpets, which tend to prevent the optimal activation of thermal mass for human comfort. The second critical topic uniquely related to acoustics and energy in office buildings is the question of open-plan office spaces. Many designs incorporate private offices at the perimeter of the building, which confines the benefits of a natural ventilation scheme to only those few individuals in the offices (many of whom are managers who may not be present as often as lower-ranked personnel). Placing open-plan spaces at the perimeter for possible energy efficiency benefits should be weighed against corporate hierarchies. The predominant use of open-plan offices spaces at the interior of the building can allow for multiple low-energy cooling techniques to be applied, such as displacement or underfloor air distribution, radiant ceilings or floors, and chilled beams. The reason

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

these low-energy systems are appropriate is that the heat loads are relatively constant and are at low density as compared to areas experiencing solar heat. The design team should acknowledge that multiple studies show that most occupants dislike the lack of acoustic privacy that arises in open-plan office spaces, regardless of cubicle partition height. Some consideration of artificial, lowenergy noise-masking white noise or pink noise speakers should be considered, especially for lowenergy HVAC systems, as their characteristically low velocities do not create that same level of white noise as overhead high-airflow systems. With regard to the speech privacy and intelligible noise issue, the design team should consider whether there are other space-planning techniques to resolve it, such as small 5×5 ft “telephone booths” that allow individuals to make private calls or that can accommodate a couple of people gathering around a phone for a teleconference to avoid irritating their neighbors.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Table 4.3. Envelope Performance – Building Physics Related Aspects

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

4.5.4. BUILDING ZONING During its space-planning exercise, the design team should spend sufficient time in discussion to understand how the building will be zoned for HVAC and lighting, as this will effect the possibility for future design applications to achieve energy efficiency. Much discussion has already been made of the benefits of understanding solar heat gain in the perimeter zone. To summarize, perimeter glazed zones can have fluctuating availability of daylighting, seasonal capacity to apply natural ventilation capacity, and extreme reactions to seasonal or diurnal changes in weather. The HVAC and lighting zoning of these spaces must be responsive through the entire range of extreme conditions. Perimeter private-office spaces should be clustered on HVAC zones based on common orientation and should take into account the political aspects related to the number of people who will be arguing over the setpoint temperature control, as usually only one office can be master but all offices will get similar quantities of cooling air. Corner offices with glazing on both façades should always be their own HVAC zones. Lastly, perimeter zones should be ducted and piped to allow for perimeter heating and nighttime building pressurization/setup and setbacks to operate while turning off all centralized air conditioning associated with the interior zones. Internal zones consisting of office occupancies usually are fairly stable with regard to heat load and occupancy and should be independently zoned to take advantage of these facts while using lower-energy systems. If nighttime shutdowns of plug-load equipment and lighting are instituted as noted above, most interior zones can suffice with shutting down the air handlers and doing a purge cycle of preconditioning in the morning. High-occupancy-density zones, such as classrooms or conference rooms/lounges, should be zoned independently from areas having more stable and lower-intensity occupancy. Highdensity areas should have occupancy-based DCV in order to automatically reduce the amount of ventilation air provided to the space and thus the amount of OA cooled or heated to suit. It is recommended that the ventilation air in these zones be decoupled if possible from the overall cooling supply. High-plugload/heat-density spaces are usually computer rooms, electrical/information technology/audiovisual/security rooms, and server rooms in office buildings. These zones should be completely independent from the rest of the building, as this equipment tends to run 24 hours per day and requires cooling throughout that period. These spaces are often best served by a local recirculation unit with a cooling coil moving large amounts of cooling air. This approach tends to significantly reduce fan energy as compared to using remote or central systems. It should be carefully noted that if a situation arises after the fact in which a space formerly designed to reside on a centralized office-type system is packed with high-plug-load electronic equipment, there is a risk for significant inefficiencies, as this one overpacked zone will drive the central air handler’s supply temperature to the minimum and the rest of the zones will experience significant reheating of the supply airstream to meet comfort conditions. In these cases, placing a local recirculation fan-coil unit in the room will help to absorb heat locally while still allowing ventilation air to come from the central system. Despite the optimally energy-efficient zoning techniques espoused above, it is sometimes the case that zoning of HVAC and lighting systems needs to occur by department for back-charging purposes. The design team should discuss the relative first cost of submetering components with the expectation of annual energy savings versus the first-cost benefits of combining disparate zones. Alternatively, per-square-foot back charges can also be calculated based on anticipated proportion of annual energy use arising for each zone, based on energy modeling.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

CHAPTER 5

ENERGYâ&#x20AC;&#x201C;EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

5.1. INTRODUCTION This chapter begins with general climate-related design strategies for Office Buildings and follows with specific recommendations for each of the five climate zones. As no single design strategy applies universally to all of the climates, each set of climate combinations needs to be analyzed separately. The general design strategies need to be considered at the preliminary stages of building design. The chapter is segmented by climate conditions of temperature (hot, warm, composite and cold) and moisture (humid and dry). Each segment addresses the key issues associated with the climate and the envelope design. The climate sections address conduction, solar loads, and moisture while the envelope sections address fenestration area, orientation, shading and also Daylighting. The recommendations are presented in five tables that contain the individual construction specifications per climate zone. Each table is subdivided into specific items that are then further subdivided into components. It is critical that the preliminary design follow the general design strategies since that is when the basic structure and form are set in terms of size, shape, and orientation. Once the basic design is set, the construction of office buildings needs to follow the prescriptive recommendations in order to achieve the 50% energy savings target as recommended by ASHRAE.

5.2. CLIMATE RELATED DESIGN STRATEGIES Both weather and climate are characterised by the certain variables known as climatic factors. They are as follows: (A) Solar radiation (B) Ambient temperature (C) Air humidity (D) Precipitation (E) Wind (F) Sky condition Regions having similar characteristic features of climate are grouped under one climatic zone. Based on the climatic factors mentioned above, the country can be divided into a number of climatic zones. Zone 1 Zone 2 Zone 3 Zone 4 Zone 5

: : : : :

Hot & Dry (Rajasthan, Gujarat, Central Maharashtra, Madhyapradesh) Warm & Humid (Kerala, Tamilnadu, Kolkata, Orissa & Andhrapradesh) Temperate or Moderate (Bangalore, Goa And Parts Of Deccan) Cold (Sunny/Cloudy) (Jammu & Kashmir, Ladakh, Himachalpradesh) Composite (Uttar Pradesh, Hariyana, Punjab, Jharkhand, Chattisgarh, Bihar)

The criteria of classification are presented in Table 4.1 and Figure 4.1(a) shows the climatic zones. A place is assigned to one of the first five climatic zones only when the defined conditions prevail there for more than six months.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

5.2.1. HOT & DRY CLIMATE ZONE

     

High temperature Hot winds during the day & cool winds at night Low humidity & rain fall Intense solar radiation & generally clear sky Sandy or rocky ground with little vegetation Low underground water table & little sources of water

Summer Midday Temperature Summer Night Temperature Winter Midday Temperature Winter Night Temperature Diurnal variation Humidity Annual Rainfall

: : : : : : :

40ºC to 45ºC 20ºC to 30ºC 5ºC to 25ºC 0ºC to 10ºC 15ºC to 20ºC 25% - 40% <500 mm

ENVELOPE DESIGN STRATEGIES A.

ORIENTATION & PLANFORM



An east-west orientation is preferred in hot and dry climatic regions.



South and north facing walls are easier to shade than east and west walls. During summer, the south wall with significant exposure to solar radiation in most parts of India, leads to very high temperatures in south-west rooms. Hence, shading of the south wall is imperative.



The surface to volume (S/V) ratio should be kept as minimum as possible to reduce heat gains.



Cross-ventilation must be ensured at temperatures during this period are low.

night

ambient

ROOF



Flat roofs or vaulted roofs are ideal in this climate. Nonetheless, a vaulted roof provides a larger surface area for heat loss compared to a flat roof.



The material of the roof should be massive; a reinforced cement concrete (RCC) slab is preferred to asbestos cement (AC) sheet roof.



External insulation in the form of mud phuska with inverted earthen pots is also suitable.



A false ceiling in rooms having exposed roofs is favourable as the space between the two acts as a heat buffer. Thermal insulation over false ceiling further increases the buffer action.



Insulation of roofs makes the buildings more energy efficient than insulating the walls.

 

Evaporative cooling of the roof surface and night time radiative cooling can also be employed. In case of evaporative cooling, it is better to use a roof having high thermal transmittance.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

WALLS



In multi-storeyed buildings, walls and glazing account for most of the heat gain.



The control of heat gain through the walls by shading, thus, becomes an important design consideration.



A wall that transmits less heat is hence feasible.

FENESTRATION



In hot and dry climates, reducing the window area leads to lower indoor temperatures.



More windows should be provided in the north facade of the building as compared to the east, west and south as it receives lesser radiation throughout the year



All openings should be protected from the sun by using external shading devices such as chhajjas and fins.



Moveable shading devices such as curtains and venetian blinds can also be used.



Ventilators are preferred at higher levels as they help in throwing out the hot air.



Since daytime temperatures are high during summer, the windows should be kept closed to keep the hot air out and opened during night-time to admit cooler air.



The use of 'jaalis'(lattice work) made of wood, stone or RCC may be considered as it they allow ventilation while blocking solar radiation. Scheduling air changes (i.e. high ventilation rate at night and during cooler periods of the day, and lower ones during daytime) can significantly help in reducing the discomfort.



The heat gain through windows can be reduced by using glass with low transmissivity.

COLOUR AND TEXTURES

    

Change of colour is a cheap and effective technique for lowering indoor temperatures. Colours that absorb less heat should be used to paint the external surface. Darker shades should be avoided for surfaces exposed to direct solar radiation. The surface of the roof can be of white broken glazed tiles. The surface of the wall should preferably be textured to facilitate self shading.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

5.2.2. WARM & HUMID CLIMATE ZONE

     

Moderately high temperature during day & night High winds from prevailing wind directions Very high humidity & rainfall Diffuse solar radiation if cloud cover is high & intense in case of clear sky Abundant vegetation Provision for drainage water is required

Summer Midday Temperature Summer Night Temperature Winter Midday Temperature Winter Night Temperature Diurnal variation Humidity Annual Rainfall

: : : : : : :

30ºC to 35ºC 25ºC to 30ºC 25ºC to 30ºC 20ºC to 25ºC 5ºC to 8ºC 70% - 90% >1200 mm

ENVELOPE DESIGN STRATEGIES A. ORIENTATION & PLANFORM



As temperatures are not very high, free plans can be evolved as long as the house is under protective shade.



An unobstructed air path through the interiors is important to ensure proper ventilation.



The buildings could be long and narrow to allow crossventilation. For example, a singly loaded corridor plan (i.e. one with rooms on one side only) is preferable over a doubly loaded one.



Heat and moisture producing areas like toilets and kitchens must be ventilated and separated from the rest of the structure.



Semiopen spaces such as balconies, verandahs and porches can be used advantageously for daytime activities as well as give protection from rainfall.



In multistoreyed buildings a central courtyard can be provided with vents at higher levels to draw away the rising hot air.

B. ROOF



In addition to providing shelter from rain and heat, the form of the roof should be planned to promote air flow.



Vents at the rooftop effectively induce ventilation and draw hot air out.



Insulation does not provide any additional benefit for a normal RCC roof in a non-conditioned building.



However, very thin roofs having low thermal mass, such as AC sheet roofing, require insulation as they tend to rapidly radiate heat into the interiors during daytime.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings



A double roof with a ventilated space in between can also be used to promote air flow. The space in between can also act as a heat buffer.

C. WALLS



The walls must also be designed to promote air flow so as to counter the prevalent humidity.



Baffle walls, both inside and outside the building can help to divert the flow of wind inside.



They should be protected from the heavy rainfall prevalent in such areas.



If adequately sheltered, exposed brick walls and mud plastered walls work very well by absorbing the humidity and helping the building to breathe.

D. FENESTRATION



Cross-ventilation is of utmost importance in warm and humid climatic regions.



All doors and windows should preferably be kept open for maximum ventilation for most of the year.



These must be provided with venetian blinds or louvers to shelter the rooms from the sun and rain, as well as for the control of air movement.



Openings of a comparatively smaller size can be placed on the windward side, while the corresponding openings on the leeward side should be bigger for facilitating a plume effect for natural ventilation.

 

The openings should be shaded by external overhangs.

Outlets at higher levels serve to vent hot air. COLOUR & TEXTURE



The walls should be painted with light pastel shades or whitewashed, while the surface of the roof can be of broken glazed tile (china mosaic flooring) to reflect the sunlight back to the environment, and hence reduce heat gain of the building.



The use of appropriate colours and surface finishes is a cheap and very effective technique to lower indoor temperatures.



The surface finish should be protected from/ resistant to the effects of moisture.

REMARKS

  

Ceiling fans are effective in reducing the level of discomfort in this type of climate.



In case of airconditioned buildings, dehumidification plays a significant role in the design of the plant.

Desiccant cooling techniques can also be employed as they reduce the humidity level. Careful water proofing and drainage of water are essential considerations of building design due to heavy rainfall.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

5.2.3. TEMPERATE CLIMATE ZONE

     

Moderate temperature High winds in summer depending on the topography of the area Moderate humidity & rainfall Same solar radiation throughout the year, clear sky Abundant vegetation Hilly of high plateau region

Summer Midday Temperature Summer Night Temperature Winter Midday Temperature Winter Night Temperature Diurnal variation Humidity Annual Rainfall

: : : : : : :

30ºC to 34ºC 17ºC to 24ºC 27ºC to 33ºC 16ºC to 18ºC 8ºC to 13ºC 60% - 85% >1000 mm

ENVELOPE DESIGN STRATEGIES A. ORIENTATION & PLANFORM

   

It is preferable to have a building oriented in the north-south direction. Living areas like bedrooms may be located on the eastern side to allow for heat penetration in the mornings, and an open porch on the south south east side allows heat gain in the winters while providing for shade in the summers. The western side should ideally be well-shaded. Humidity producing areas must be isolated. Sunlight is desirable except in summer, so the depth of the interiors need not be excessive.

B. ROOF



Insulating the roof does not make much of a difference in the moderate climate.

D. WALLS



Insulation of walls does not give significant improvement in the thermal performance of a building.

E. FENESTRATION

   

The arrangement of windows is important for reducing heat gain. Windows can be larger in the north, while those on the east, west and south should be smaller. All the windows should be shaded with chajjas of appropriate lengths. Glazing of low transmissivity should be used.

F. COLOUR & TEXTURE



Pale colours are preferable; dark colours may be used only in recessed places protected from the summer sun.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

5.2.4. COLD (SUNNY/CLOUDY) CLIMATE ZONE

     

Moderate summer temperature & very low temperature in winter Cold winds in winter Low humidity in cold/sunny & high humidity in cold/cloudy Low precipitation in cold/sunny & high in cold/cloudy High solar radiation in cold/sunny & low in cold/cloudy Very little vegetation in cold/sunny & abundant in cold/cloudy

Summer Midday Temperature Summer Night Temperature Winter Midday Temperature Winter Night Temperature Diurnal variation Humidity Annual Rainfall

: : : : : : :

17ºC to 24ºC / 4ºC to 11ºC / -7ºC to 8ºC / 0ºC to 10ºC 15ºC to 25ºC / 10% - 50% / <200 mm /

20ºC to 30ºC 17ºC to 21ºC 4ºC to 8ºC 5ºC to 15ºC 70% - 80% >1000 mm

ENVELOPE DESIGN STRATEGIES A. ORIENTATION & PLANFORM

   

Buildings must be compact with small surface to volume ratios to reduce heat loss. Windows should face south to facilitate direct gain. The north side of the building should be well-insulated. Living areas can be located on the southern side while utility areas such as stores can be on the northern side.

 

Air-lock lobbies at the entrance and exit points of the building reduce heat loss. Heat generated by appliances in rooms such as kitchens may be used to heat the other parts of the building.

B. ROOF



False ceilings with internal insulation such as polyurethane foam (PUF), thermocol, wood wool, etc. are feasible for houses in cold climates.



Aluminium foil is generally used between the insulation layer and the roof to reduce heat loss to the exterior.



A sufficiently sloping roof enables quick drainage of rain water and snow.



A solar air collector can be incorporated on the south facing slope of the roof and hot air from it can be used for space heating purposes.



Skylights on the roofs admit heat as well as light in winters.

C. WALLS

 

Walls should be made of materials that lose heat slowly. The south-facing walls (exposed to solar radiation) could be of high thermal capacity (such as Trombe wall) to store day time heat for later used.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

 

The walls should also be insulated.

  

Hollow and lightweight concrete blocks are also quite suitable.

The insulation should have sufficient vapour barrier (such as two coats of bitumen, 300 to 600 gauge polyethylene sheet or aluminium foil) on the warm side to avoid condensation. Skylights can be provided with shutters to avoid over heating in summers. On the windward or north side, a cavity wall type of construction may be adopted.

D. FENESTRATION



It is advisable to have the maximum window area on the southern side of the building to facilitate direct heat gain.

  

They should be sealed and preferably double glazed to avoid heat losses during winter nights. Condensation in the air space between the panes should be prevented, Movable shades should be provided to prevent overheating in summers.

E. COLOUR & TEXTURE



The external surfaces of the walls should be dark in colour so that day absorb heat from the sun.

5.2.5.

     

COMPOSITE CLIMATE ZONE

High temperature in summer & cold in winter Hot winds in summer, cold winds in winter & strong winds in monsoon Low humidity in summer & high in monsoon High direct solar radiation in all seasons except monsoon when high diffused radiation is found Occasional hazy sky Variable landscape & seasonal vegetation

Summer Midday Temperature Summer Night Temperature Winter Midday Temperature Winter Night Temperature Diurnal variation Humidity Annual Rainfall

: : : : : : :

32ºC to 43ºC 27ºC to 32ºC 10ºC to 25ºC 4ºC to 10ºC 35ºC to 22ºC 20% - 50% (Dry periods), 50% - 95% (Wet periods) 500 mm – 1300 mm, During monsoon reaches 250mm

ENVELOPE DESIGN STRATEGIES A. ORIENTATION & PLANFORM



An east-west orientation is preferred as northern and southern walls are easier to shade.



During summer, the south wall which gets significant exposure to solar radiation in most parts of India, leads to very high temperatures in south-west rooms. Hence, shading of the south wall is imperative.



The surface to volume ratio should be kept as minimum as possible to reduce heat gains.



Cross-ventilation must be ensured at night as ambient temperatures during this period are low.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

B. ROOF

 

Flat roofs may be used in this climate.

   

External insulation in the form of mud phuska with inverted earthen pots is quite suitable.



Incase the former is used, it is better to have a roof that will cool down fast.

A massive roof structure like a reinforced cement concrete RCC slab is preferrable over an asbestos cement AC sheet roof. A false ceiling in rooms having exposed roofs can help in reducing the discomfort level. Provision of roof insulation yields greater lifecycle savings compared to walls in this climate. Evaporative cooling of the roof surface and night-time radiative cooling are measures that can also be employed to improve comfort levels.

A. WALLS



In multi-storeyed buildings, walls and glazing account for most of the heat gain. So, the control of heat gain through the walls by shading is an important consideration in building design.



A wall that takes a longer time to heat up reduces the heat gain.

A. FENESTRATION

 

Minimising the window area leads to lower indoor temperatures.



All openings should be protected from the sun by using external shading devices such as chhajjas and fins.

 

Moveable shading devices such as curtains and venetian blinds can also be used.



The use of 'jaalis'(lattice work) made of wood, stone or RCC may be considered as they allow ventilation while blocking solar radiation. Measures to control ventilation of the building as and when required makes it more comfortable indoors.



The heat gain through windows can be reduced by using glass with low transmissivity.

More windows should be provided in the north facade of the building as compared to the east, west and south as it receives lesser radiation during the year.

Since daytime temperatures are high during summer, the windows should be kept closed to keep the hot air out and opened during night time to admit cooler air.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

A. COLOUR & TEXTURE

    

Change of colour is a cheap and effective technique for lowering indoor temperatures. Colours having low absorptivity should be used to paint the external surface. Darker shades should be avoided for surfaces exposed to direct solar radiation. The surface of the roof can be of white broken glazed tiles. The surface of the wall should preferably be textured to facilitate self shading.

REMARKS



As the winters in this region are uncomfortably cold, windows should be designed such that they encourage direct gain of solar heat during this period.



Deciduous trees can be used to shade the building during summer and admit sunlight during winter.



Well-insulated and very thick walls give a good thermal performance if the glazing is kept to a minimum and windows are well shaded.



In case of non-conditioned buildings, a combination of insulated walls and high percentage of glazing will lead to very uncomfortable indoor conditions.



Indoor plants can be provided near the window, as they help in evaporative cooling and in absorbing solar radiation.

 

Evaporative cooling and earth air pipe systems can be used effectively in this climate. Desert coolers are extensively used in this climate, and if properly sized, they can help in achieving comfort levels.

Figure 5.1. Location Map showing of Five Climate Zones of India

ENERGYâ&#x20AC;&#x201C;EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

5.3. CLIMATE ZONE RECOMMENDATIONS Based on the characteristics of the five different climate zones the thermal comfort requirements in buildings and their physical manifestation in architectural form are also different for each climate zone. These comfort requiements and physical manifestations are shown in Table 5.1.

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

Table 5.1. Thermal Requirements & Physical Manifestatin for different Climate Zones

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

5.4. IMPLEMENTATION OF RECOMMENDATIONS When a recommendation is provided, the recommended value differs from the requirements in Ashrae Standard 90.1–2004. When “No recommendation” is indicated, the user must meet the more stringent of either the applicable version of Standard 90.1 or the local code requirements. Each of the recommendation tables includes a set of common items arranged by building subsystem: envelope and daylighting/lighting. Recommendations are included for each item, or subsystem, by component within that subsystem. For some subsystems, recommendations depend on the construction type. For example, insulation values are given for mass and steel-framed and wood-framed wall types. For other subsystems, recommendations are given for each subsystem attribute. For example, vertical fenestration recommendations are given for thermal transmittance, SHGC, and exterior sun control. The recommendations presented are minimum, maximum, or specific values (which are both the minimum and maximum values). Minimum values include values for the following:

               

R-value Solar Reflectance Index (SRI) Visible transmittance (VT) Vertical fenestration effective aperture (EA) Interior surface average reflectance Mean lumens per watt (LPW) Gas water heater or boiler efficiency Thermal efficiency (Et) Energy factor (EF) Energy efficiency ratio (EER) Integrated energy efficiency ratio (IEER) Integrated part-load value (IPLV) Coefficient of performance (COP) Energy recovery effectiveness Fan or motor efficiency Duct or pipe insulation thickness

Maximum values include values for the following:

      

Fenestration and door U-factors Fenestration solar heat gain coefficient (SHGC) Lighting power density (LPD) Fan input power per cubic foot per minute of supply airflow Window-to-wall ratio (WWR) External static pressure (ESP) Duct friction rate

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5.4.1. HOT & DRY CLIMATE ZONE RECOMMENDATION TABLE FOR SMALL TO MEDIUM OFFICE BUILDINGS

ENERGY–EFFICIENT BUILDING ENVELOPE DESIGN & PERFORMANCE ASSESSMENT : Special Emphasis On Office Buildings

5.4.2. WARM & HUMID CLIMATE ZONE RECOMMENDATION TABLE FOR SMALL TO MEDIUM OFFICE BUILDINGS

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5.4.3. TEMPERATE CLIMATE ZONE RECOMMENDATION TABLE FOR SMALL TO MEDIUM OFFICE BUILDINGS

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5.4.4. COLD (SUNNY/CLOUDY) CLIMATE ZONE RECOMMENDATION TABLE FOR SMALL TO MEDIUM OFFICE BUILDINGS

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5.4.5. COMPOSITE CLIMATE ZONE RECOMMENDATION TABLE FOR SMALL TO MEDIUM OFFICE BUILDINGS

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CHAPTER 6

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6.1. INTRODUCTION 6.1.1.LEED SCHEME LEED (Leadership in Energy & Environmental Design) Green Building Rating System is a voluntary, consensus-based standard for developing high performance, sustainable Buildings. Its goal is to evaluate environmental performance from the whole building perspective over complete building’s life cycle, providing a definitive standard for what constitutes a ‘Green Building’. LEED is the most widely recognised building environmental assessment scheme used in 24 different countries. The current version for new construction is LEED-NC v2.2, which is based on a set of prerequisites and credits mentioned below :

     

Sustainable Sites Water Efficiency Energy and Atmosphere Materials and Resources Indoor Environmental Quality Innovation and Design

One point will be awarded to each credit when the requirement are met except for the energy performance credit and the renewable energy credit in which a number of points will be awarded to each credit depending on by how much performance improvement is achieved. This counts towards the total scoring system. There are up to 69 points that can be achieved. Based on the awarded points, there are four levels the buildings can qualify, which are

   

LEED Certified (26-32 points) Silver (33-38 points) Gold (39-51 points) Platinum (52-69 points)

6.1.2. LEED EA CREDIT 1 COMPLIANCE PATHS There are two approaches to assess building energy performance known as Credit EA1-Optimize Energy Performance. The first is the Prescriptive Compliance Path, which allows certain projects to achieve up to 4 points when they meet the prescriptive measures of the ASHRAE Advanced Energy Design Guide for Small Buildings. The other approach is the Whole Building Energy Simulation, which allows up to 10 points when the building demonstrates improvement on energy cost against a normalised building. For both approaches, the assessed building needs to meet a minimum performance level, which is 2 points. Table 6.2 lists the credit points that are related to the percentage of improvement.

The Whole Building Energy Simulation, which counts for 14.5% of the total scheme points, requires the use of a simulation program that can perform thermal analysis to the specifications that are laid down by ASHRAE Standard 90.1-2004, known as Performance Rating Method (PRM).

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The method specifies that two types of building models are created. The first is the proposed building model and the second is the baseline building model. The baseline building needs to be set up with orientations of 0, 90,180 and 270 degrees respectively in order to normalise the self-shading effect. Table 6.2 shows the main requirements for setting up these two building models. The energy rating is calculated based on the annual energy cost of running the proposed building against the average annual cost of running the baseline building by using actual rates for purchased energy or State average energy prices, as displayed below. Percentage of improvement=100 Ă&#x2014; [1-(Cost of Proposed/Average Cost of Baseline)]

Table 6.1. General Information on LEED Rating System

Table 6.2. Points awarded for Credit EA-1 of Optimize Energy Performance for LEED-NC v2.2

Figure 6.1. Flow chart of methodology used for energy performance assessments in LEED

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Table 6.3. LEED Performance Rating Method (PRM) For Proposed and Baseline Building Models

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6.2. ENERGY MODELING REQUIREMENTS The methodology described in ASHRAE 90.1–2007 involves the generation of two energy models: 1.Representing a baseline minimum-standard building, 2. Representing the proposed building with all its designed energy enhancements. Table 6.4 summarizes the modeling requirements for typical projects as recommended by ASHRAE 90.1–2007. Since project specific information may vary, project teams should refer to the referenced standard for all applicable details and modeling requirements. LEED-CS, LEED for Schools, LEED for Commercial Interiors (CI), LEED for Retail (NC and CI), and LEED for Healthcare are identical to LEEDNC except as noted in this table. For LEED-CI projects, the simulation should use either the energy cost budget method or the performance rating method. If served by a common building HVAC system, a LEED-CI project should include both the project space and the building segment that uses the common HVAC system.

Table 6.4. Details of Modeling Requirements for ASHRAE 90.1–2007

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Table 6.5. Details of Modeling Requirements for ASHRAE 90.1–2007

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6.3. SIMULATION SOFTWARE 6.3.1. OVERVIEW ASHRAE 90.1–2007, requires that a qualified simulation program explicitly model all of the following:

       

8,760 hours per year; Hourly variations in occupancy, lighting power, miscellaneous equipment power, thermostat setpoints, and HVAC system operation; Thermal mass effects; 10 or more thermal zones; Part-load performance curves for mechanical equipment; Capacity and efficiency correction curves for mechanical heating and cooling equipment; Air-side economizers with integrated control; and Baseline building design characteristics specified in ASHRARE 90.1–2007, Appendix G, Section 3.

6.3.2. GENERAL REQUIREMENTS



The simulation program must be able either to directly determine the proposed energy use and code baseline energy use or to produce hourly reports of energy use, by energy source, suitable for determining the proposed energy use and code baseline energy use using a separate calculation engine.



The simulation program must also be capable of performing design load calculations to determine required HVAC equipment capacities and airflow and water flow rates in accordance with generally accepted engineering standards and handbooks (e.g., ASHRAE Handbook of Fundamentals) for both the proposed building design and the code baseline building design.



The simulation program must include calculation methodologies for the building components being modeled. For components that cannot be modeled by the simulation program, the exceptional calculation method requirements in the standard may be used. In addition, a thermodynamically similar component model that can approximate the expected performance of the component may be substituted.



Commonly used modeling software packages for ASHRAE 90.1–2007, Appendix G, include DOE2-based modeling programs (eQuest, EnergyPro, and VisualDOE), TRACE, HAP, IES, VisualDOE, and EnergyPlus. This section offers brief descriptions of eQUEST since it is the most commonly and widely used simulation software required for energy analysis.



Energy modeling software packages have differing approaches for building the ASHRAE 90.1– 2007 Appendix G baseline building model. In some cases, the baseline is automatically defined within the software, based on the proposed case inputs; in other cases the user follows prompts to build the baseline model using certain predefined input parameters built into the software program; in still other cases, the user must build the entire baseline model.



In all cases, the modeler is encouraged to verify the baseline inputs in the software package against the baseline requirements of ASHRAE 90.1–2007 to confirm conformance to the Appendix G requirements before submitting the results for a preliminary LEED review.

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6.4. DOE-2–BASED SOFTWARE : eQUEST 6.4.1. INTRODUCTION DOE-2 is a publicly available simulation software engine which simulates the hourly energy use and energy cost of a building based on hourly weather information and description of the building, its HVAC equipment, and the utility rate structure. Several front-end programs have been developed that give DOE-2 a user-friendly input interface and generate formatted output reports. DOE-2 based modeling software for the EA Credit 1 performance compliance path using ASHRAE Appendix G includes DOE2.1e (VisualDOE) and eQuest. The latter is a free building energy analysis simulation program widely used for LEED projects.

6.4.2. SIMULATION BASICS



eQuest is a tool from the Department of Energy (DOE). It takes the difficult interface of the more common and helpful DOE-2 and simplifies it.



eQuest can model buildings with multiple zones and interface with AUTOCAD to set up the floor and zone geometry and layout. The program can provide detailed modeling output files.



eQuest has a function where energy efficiency measures can be created and manipulated to see the resulting changes to a model.



eQquest also has a life cycle cost analysis tool for each ecm applied to the model.



eQuest also has the opportunity to input several different utility bill rates and structures to find the annual cost difference for changing ESCOs.



Utility rates can be complicated, and eQuest is equipped to handle the most complex billing structures.

Figure 6.2. Basic Action Panel of eQuest

6.4.6. OVERVIEW OF THE PROCESS



eQuest calculates hour by hour building energy consumption over an entire year (8,760 hours) using hourly weather data for the location under consideration.



Input to the program consists of a detailed description of the building being analyzed, including hourly scheduling of occupants, lighting, equipment and thermostat settings as shown in Table 6.6.



eQuest also contains a dynamic daylighting model to assess the effect of natural lighting on thermal and lighting demands.



The simulation process begins by developing a “model” of the building based on building plans and specifications. The model can also be developed by importing AutoCad Drawings into eQuest.



A base line building model that assumes a minimum level of efficiency (e.g., minimally compliant with ASHRAE 90.1) is then developed to provide the base from which energy savings are

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estimated. Alternative analyses are made by making changes to the model that correspond to efficiency measures that could be implemented in the building.

ď&#x201A;§

These alternative analyses result in annual utility consumption and cost savings for the efficiency measure that can then be used to determine simple payback, life-cycle cost, etc. for the measure and. ultimately, to determine the best combination of alternatives.

6.4.7. DATA REQUIREMENTS The following table shows the lists of data fed into the software for a building project in order to generate a simulation model which then gives performance analysis :

Table 6.6. Data Requirement prior to developing the Simulation Model

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Table 6.7. Data Requirement prior to developing the Simulation Model (Continued)

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6.4.8. COMPUTATIONAL STEPS IN eQUEST To better understand the results and limitations of eQUESt’s DOE-2- engine, it is helpful to be familiar with the generic computational steps DOE-2 has always gone through in its simulation. The sequence illustrated below depicts seven broad steps of calculations performed hourly by eQUEST. These seven steps occur within four overall areas of the program – Loads, Systems, Plants and Economics. Understanding this sequence is important to understanding the detailed reports produced by eQUESTs DOE-2 -derived engine.

Figure 6.3. Four basic areas for performing hourly calculations in eQUEST

STARTING WITH A PROJECT

GENERAL INFORMATION OF THE PROJECT & SITE

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BUILDING FOOTPRINT & ORIENTATION

CUSTOMIZED BUILDING FOOTPRINT BY IMPORTING DWG FILES

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BUILDING ENVELOPE CONSTRUCTIONS

BUILDING INTERIOR CONSTRUCTIONS

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EXTERIOR DOORS

EXTERIOR WINDOWS

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EXTERIOR WINDOW SHADES

ROOF SKYLIGHTS

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DAYLIGHT ZONING FOR EACH FLOOR

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ACTIVITY AREAS ALLOCATION

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OCCUPIED LOADS BY ACTIVITY AREA

UNOCCUPIED LOADS BY ACTIVITY AREA

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MAIN SCHEDULE INFORMATION

ENERGY EFFICIENCY MEASURES WIZARD

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PARAMETRIC RUNS – GRAPHICAL REPORTS After all of the simulation runs have completed, from the eQUEST analysis tool bar, press the Results Review mode button to view graphic simulation output reports & from the bottom of the results tree diagram select the

tab, then select one or more projects for which you wish to view

results. Also from the bottom of the results tree diagram, select the tab, then select single run or comparison reports, as preferred. Examples of all the available graphical reports are presented below :

Figure 6.4. Single Run Report on Annual Energy Consumption by End Use

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Figure 6.5. Single Run Report on Monthly Energy Consumption by End Use

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Figure 6.6. Single Run Report Showing Monthly Utility Bills

Figure 6.7. Single Run Report on Annual Peak Demand by End Use

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Figure 6.8. Single Run Report on Monthly Peak Demand on End Use

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Figure 6.9. Comparison Report on Monthly Total Energy Consumption

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Figure 6.10. Comparison Report of Monthlu Utility Bills

Figure 6.11. Comparison Report of Annual Energy by End Use

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CHAPTER 7A

PRIMARY CASE STUDY SMALL OFFICE BUILDING

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7.1. OVERVIEW OF THE PROJECT 7.1.1. PROJECT BRIEF ECB (Eco Commercial Building) is a commercial building, being developed by Bayer Material Science Pvt. Ltd. and designed by Sankalpan Architects. The building consists of G +1 floors with a usable area of 930 square meters for approximately 50 employees and an adjoining display hall that covers around 1,000 square meters and have a ceiling height of six meters. Building fenestration is designed such that there is adequate daylight coming into the office space. Following over a year of net positive operational energy performance, Bayer’s 930 square meters office building outside New Delhi achieved LEED Platinum status in May 2012 with an impressive 64 out of 69 possible points, officially making it the highest-rated LEED new construction project in the world. It is determined via simulation that the project with the help of onsite photovoltaic electricity generation saves 100 % in Energy costs over the LEED mandated ASHRAE 90.1-2004 baseline and shall achieve ten (10) LEED points for Energy and Atmosphere credit 1.0. LOCATION Greater Noida, Uttar Pradesh PROJECT OWNER Bayer Material Science Pvt. Ltd. ARCHITECT Sankalpan Architects BUILDING TYPE Small Office Building BUILT UP AREA 930 square meters CONCEPT Zero-emissions building

Figure 7.1. India’s First Net Zero Energy building ECB located in Greater Noida, Uttar Pradesh

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7.1.2. BRIEF SPECIFICATIONS Eco Commercial building claims to be the Modern Net Zero Energy Building as it reduces the building energy demand by incorporating active and passive strategies that enable efficient design, environmentally safe construction materials and an integrated project delivery approach. Following are the basic features observed in the design of the building :



NET ZERO ENERGY BUILDING First Net positive energy building in India achieving 100% on-site energy generation through the use of a 57 KW Photovoltaic System spread over a total surface area of 444 sq m.



BATTERY BACK-UP A 24 hour autonomous operation of the building independent of the electrical grid through the use of battery back up has been achieved.



ZERO CARBON EMISSION 100% regenerative, thus carbon oxide (CO2) free, supply of heating, cooling and electrical energy through photovoltaic cells.



INDEPENDENT OPERATION 8 hours of operations independently. This means if there is a power outage the building must continue to function fully for minimum 8 hours without impacting infrastructure.



ZERO RUN-OFFS Zero run-off implying that the aim is to operate the building as far as possible without generating waste water.



COST EFFECTIVENESS Actual on-site generation at ECB is 72,023 kWh which is in addition of 8113 kWh over the 63,910 kWh consumed annually, enabling its net positive building status as elaborated in Table 7.1. There by through the actual on-site energy generation the project is able to achieve the reduction in the energy cost of approximately Rs. 3,60,000 each year. ECB PARAMETERS

ACTUAL GENERATION AT SITE THROUGH PVS

ACTUAL ENERGY CONSUMPTION AT SITE THROUGH PVS

ADDITIONAL ENERGY GENERATED AT SITE

Annual Energy (kWh/yr)

72,023

63,910

8113

Carbon Reduces (kg/yr)

67,918

60,267

7651

58.41

51.83

6.58

Pollution Pollution (Equivalent forest grown)

Table 7.1. Annual Energy Consumption chart of ECB, Greater Noida



ORIENTATION Orientation of the building to harness diffused daylight from the façade facing north direction.



ENVELOPE DESIGN 150mm thick AAC blocks with 75mm thick polyurethane foam sandwiched externally are used for the envelope design. For roofs 75mm thick polyurethane foam laid over-deck integrated with water proofing and additional 50mm wool are used. Windows are designed with High Performance Glazing system.

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Typically in internal loads dominated building, properly specified fenestrations achieve energy efficiency of 10-40% in lighting and HVAC. To explore this potential the evaluation of a building envelope design was carried out to analyze its effect on cooling loads and dayljghting Through several iterations, envelope specifications as suggested in Table 7.2 where identified that yielded highest resistance and minimum payback period. SL. NO.

ENVELOPE PARAMETERS

PERFORMANCE

COMMENTS

Walls

U-value : 0.04 Btu/hr.ft2 degreeF

75mm thick polyurethane foam sandwiched externally + 150mm thick AAC block walls

Roof

U-value : 0.03 Btu/hr.ft2 degreeF

75mm thick polyurethane foam laid over-deck integrated with water proofing and additional 50mm thick mineral wool

Glazing in Reception

U-value : 0.27 Btu/hr.ft2 degreeF SC : 0.31 VLT : 50%

High Performance Glass

Glazing in other Orientation

U-value : 0.24 Btu/hr.ft2 degreeF SC : 0.31 VLT : 49%

High Performance Glass

Table 7.2. Envelope Optimization Strategies applied in ECB

A Window-Wall Ratio (WWR) of 33.8% has been incorporated to ensure maximum daylighting potential with minimum solar heat gains. An enhanced Envelope and maximized WWR optimized the energy demand as well a reduced the size and cost of HVAC system needed to maintain adequate building pressurization, good indoor air quality and a comfortable thermal environment for the building occupants.



HEAT LOAD REDUCTION The terrace is projected on all the four sides such that it protects the lower floors from direct sunlight thus reducing the heat load internally. The entire terrace area has been utilised for installation of photovoltaic cells of required capacity.



RENEWABLE ENERGY THROUGH SOLAR PV Renewable energy sources like a photovoltaic array on the roof, power the building, which is designed to function for up to eight hours off-power without any impact on the infrastructure. Crystalline silicon grid connected solar PV with the capacity of 57kWp is used for this purpose.



ACTIVE CHILLED BEAMS Use of chilled beams to provide cooling there by cutting down the operational cost due to savings in AHU fan energy and simultaneous reduction in chiller energy as beams carry chilled water at 15 degC as against the conventional practice of 7 degC.



INDOOR AIR QUALITY The building is equipped with Dedicated Outdoor Air System (DOAS) and Demand Control Ventilation (DCV). doas caters to the entire latent loads of the building. dry outdoor ventilation air is supplied through an externally mounted unit that dehumidifies the air before supplying it to

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occupied spaces. This dry outdoor air acts as primary air to the chilled beams. DOAS has a heat recovery section as well, that provides a way of recovering waste energy from building exhaust. The energy recovery wheel enabled reduction of the ventilation AC load by 80%, there by minimizing operating energy as well as the size of the air conditioning equipments.



LIGHTING DESIGN Since ECB is a day-use building thereby efforts had been undertaken to ensure maximum daylighting in all Occupied spaces. Simulation softwares like Radiance, DIALux were used to evaluate the impact of various shading devices over windows that ensured a glare-free light in the indoor spaces. The main objective of design exercise was to ensure that the use of blinds or curtains on windows to be avoided without compromising on visual comfort of occupants. The selection of energy efficient fixtures & ballast enabled in achieving 37% energy efficiency in lighting. 87% of the total regularly occupied spaces in the building have a minimum daylight factor of 2%. Benefits from daylighting are further maximized from occupancy censors in normally unoccupied areas like stores, toilets etc. to minimize misuse.



USE OF HIGHLY EFFICIENT TECHNOLOGIES High performance technologies such as BMS polyurethane insulating materials, combined with extensive daylighting, LED illumination, and photovoltaic shades bolster the structure’s ultraconservative energy consumption profile.



Other environmentally conscious elements include rain water harvesting and grey water systems as well as low-VOC protective coatings, paints and flooring materials from BMS.

Figure 7.2. Energy Flow chart showing Comparison of Optimized Energy Demand and Renewable Energy Supply of ECB

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Figure 7.3. Ground Floor Plan of the Building

Figure 7.5. North side Viw of Eco Commercial Building

Figure 7.4. Detailed section of the Facade

Figure 7.6. Solar PV Panels on Terrace

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7.2. CLIMATIC ANALYSIS 7.2.1 WEATHER DATA SUMMARY New Delhi has the humid subtropical climate with high variation between summer and winter temperatures and precipitation. But New Delhi's noticeably different from many other cities with the same climate. It features long and very hot summers, relatively dry and cool winters, and monsoon and dust storms. More specifically, summer is from early April to October while winter starts in November and peaks in January. As shown in the table 7.2, January has the lowest ‘average temperature’ which is 14.1 °C (57.4 °F). On the other hand, the highest ‘average temperature’ is in the June (33.8 °C (92.8 °F)).

Table 7.3. 24-hr Average Temperature of New Delhi

7.2.2 AVERAGE AND RECORD HIGH AND LOW TEMPERATURE As shown in the table 7.3, the highest ‘average high temperature’ is in the May, which is 39°C (102°F) while the lowest ‘average temperature’ is in the January, which is 7°C (45°F). In terms of record temperature, the highest ‘record high temperature’ is 47°C (117°F) in May and July and the lowest ‘record low temperature’ is -1°C (30°F) in January.

Table 7.4. Climate Data for New Delhi

7.2.3 PRECIPITATION Table 7.4 is the average rainfall data in New Delhi. The overall Average Rainfall during the whole year is 706.4 mm (27.8 inches). From June to October some areas facing the sea, rainfall can be very heavy indeed. In July and August, the average rainfall reaches the biggest which is 200.4 (7.9 inches) and 200.3 (7.9 inches), respectively. But, there is only 3.0 mm (0.1 inches) in November.

Table 7.5. Average Rainfall in New Delhi

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7.3. IMPLEMENTATION OF ENERGY SIMULATION 7.3.1. e-QUEST ENERGY ANALYSIS The projects have been modeled using the e-QUEST energy analysis software. E-QUEST uses the DOE 2.1 Building energy simulation engine. It has the ability to explicitly model all of the following:

 

8,760 hours per year

  

Thermal mass effects

Hourly variations in occupancy, lighting power, miscellaneous equipment power, thermostat set points, and HVAC system operation, defined separately for each day of the week and holidays Part-load performance curves for mechanical equipment Capacity and efficiency correction curves for mechanical heating and cooling equipment

Figure 7.8. 3D View showing Model Graphic Rendering

Figure 7.7. Representative plan showing Zoning

Figure 7.9. Schematic Section of the Building

7.3.2. SIMULATION RESULTS BASECASE ENERGY CONSUMPTION The Basecase model is based upon the proposed design, but the performance parameters listed are defined to reflect the minimum efficiency levels that ASHRAE 90.1-2004 defines for various building components. Detailed input parameters are listed at the end of this report. Based on the energy simulation results, it is observed that the averaged basecase building consumes a total of 433.1 MBTU/yr at an Energy Use Index (EUI) of 45.58 KBTU/sqft/yr. The primary energy end-uses are equipment (25%) followed by cooling (24%), exterior lighting (24%) and fans (20%) as illustrated by the following charts.

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Figure 7.11. ENERGY-USE COMPARISON FOR ALL END-USES BASECASE (MBTU)

Figure 7.10.. ENERGY-USE COMPARISON FOR ALL END-USES BASECASE (MBTU)

Detailed investigation into the result suggests that Envelope loads (43.1%) form the largest component of HVAC requirement followed by internal loads (34%) and Fresh air loads (22.9%). The results are as-expected for the project climate (composite) and building type (commercial).

DESIGN CASE ENERGY CONSUMPTION In accordance with the above breakdown, the proposed design incorporates a high performance envelope and an efficient HVAC system (27% better than basecase). These two strategies offer the biggest potential for energy savings. Additional savings are achieved by reducing fresh air loads by incorporating strategies like demand controlled ventilation and exhaust air energy recovery. Detailed performance parameters for the proposed design case are listed at the end of this report. Overall, the proposed case shows an EUI of 29 KBTU/sqft/yr achieving energy savings of 36.32% over basecase. ENERGY COST COMPARISON The design case shows annual utility cost savings of 36.32% over the basecase. The table below lists the costs related parameters (Based on Rs. 5/kWh). FUEL TYPE

BASE CASE

DESIGN CASE

Electricity

6,34,600

4,04,110

Total

6,34,600

4,04,110

Additionally, on-site photovoltaic array would generate 88.9 MWh of annual electricity reducing all the design case energy costs which increases the energy cost savings to 100% over the basecase. Based on these results, the project should achieve all Ten (10) points under IGBC LEED NC EAc1.

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Figure 7.12. ENERGY-USE COMPARISON FOR ALL END-USES BASECASE vs DESIGN CASE (MBTU)

Table 7.6. Energy Cost Summary for Basecase and Proposed case generated using e-QUEST Simulation

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DETAILED ENERGY MODEL INPUT PARAMETERS

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DETAILED ENERGY MODEL INPUT PARAMETERS

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7.4. IDENTIFICATION OF DESIGN PARAMETERS 7.4.1. BASIC DESIGN PARAMETERS The basic design parameters considered while analyzing the energy simulation methods are mentioned below :

  

SITE LOCATION GEOGRAPHIC LOCATION ALTITUDE Summer



Greater Noida, Uttar Pradesh 28.35 Deg. N.latitude 233 m above mean sea level 107 Degree F :(42 Degree C) DB

75 Degree F :(24 Degree C) WB

Monsoon

95 Degree F :(35 Degree C) DB

83 Degree F :(28 Degree C)WB

Winter

42 Degree F :(5.5 Degree C) DB

41 Degree F :(5 Degree C)WB

FLOOR

CONDITIONED AREA (SQ. FT)

GROSS BUILT UP AREA (SQ. FT.)

Ground Floor

3,825

5,207

First Floor

3,326

4,293

Total

7,151

9,500

BUILDING AREAS

BUILDING OPERATION SCHEDULES

Figure 7.13. Profile showing Loads of Lighting, Equipment and Occupancy



TEMPERATURE PROFILE

Figure 7.14. Comparison of Heating and Cooling Temperature Profiles

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7.4.2. ENVELOPE DETAILS



ROOF



EXTERNAL WALL (TYPE 1)

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

EXTERNAL WALL (TYPE 2)



WINDOW FRAME CONDUCTANCE FOR BASECASE

The frames are unlabeled and an area weighted frame width of 1.3 inches for each window is calculated for the Design model. The frame conductance considered for evaluation is 1.8 Btu/h-sqft F based on Aluminum Frame without thermal break, fixed double glazed windows.

7.4.3. DETAILS OF AIR HANDLING UNITS

Fan Power calculation for basecase is based on ASHRAE 90.1.2004 section G3.1.2.9.

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7.4.4. CALCULATION OF FRESH AIR

7.4.5. EXTERIOR LIGHTING CALCULATIONS

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7.4.6. DETAILS OF INSTALLED SOLAR PHOTOVOLTAIC

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7.5. SIMULATION OUTPUT SUMMARY 7.5.1. UNMET HOURS FOR BASECASE AT 0 DEGREE ROTATION :

7.5.2. UNMET HOURS FOR DESIGN CASE :

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7.5.3. ENERGY COST SUMMARY FOR BASECASE :

7.5.4. ENERGY COST SUMMARY FOR PROPOSED CASE :

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CHAPTER 7B

SECONDARY CASE STUDY MEDIUM OFFICE BUILDING

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7.6. OVERVIEW OF THE PROJECT 7.6.1. PROJECT BRIEF Delta India Electronics is a commercial building, being developed by Delta Group in Gurgaon, India. The building is designed by “Sijcon Architects”. The building consists of G+3 floors and one basement. The construction of the building finished on May 2011. The total built up area of the office building is 102,840 sq.ft with a conditioned area of approximately 73,000 sq.ft. The overall window to wall ratio is approximately 38%. It is determined via simulation that the Design case achieves 39.89% savings in Energy costs over the Basecase and shall achieve Nine (9) points for E&A Cr-1. LOCATION Gurgaon, Haryana, India PROJECT OWNER Delta Group ARCHITECT Sijcon Architects BUILDING TYPE Medium Office Building BUILT UP AREA 102,840 sq.ft PROJECT COST Rs. 5,00,000,000

Figure 7.14. LEED Platinum Rated Office Building in Gurgaon : Delta India Electronics

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7.6.2. BRIEF SPECIFICATIONS This new LEED Platinum rated green corporate office in India supports the green mission and it also demonstrates the significant growth of Delta India Electronics by providing energy efficient solutions as well as being environmentally conscious by reducing waste and carbon emissions around the world. Following are the basic features observed in the design of the building :



ENERGY EFFICIENCY The building consists of Energy efficient architecture, eco-friendly building materials and building management systems that provide a vibrant clean, healthy and safe workplace for employees.



ZERO CARBON EMISSION 100% regenerative, thus carbon oxide (CO2) free, supply of heating, cooling and electrical energy through photovoltaic cells.



INDEPENDENT OPERATION 8 hours of operations independently. This means if there is a power outage the building must continue to function fully for minimum 8 hours without impacting infrastructure.



35% ENERGY SAVINGS COMPARED TO A CONVENTIONAL BUILDING A rooftop solar energy solution with a capacity of around 55 kWh of energy, use of LED streetlights, T5 and LED lighting, natural light harvesting, screw compressor based water chillers with COP (coefficient of performance) of 6, and primary variable pumping coupled with heat recovery wheel;



40% REDUCTION IN WATER COMPARED TO A CONVENTIONAL BUILDING Installation of an anaerobic sewage treatment plant, use of recycled water for non-consumption applications such as flushing and gardening purposes, rainwater harvesting pits, grasscrete for surface water recharge, and local low water consuming plantation;



ECO-FRIENDLY MATERIALS Use of autoclaved aerated blocks, fly ash in the concrete aggregate mix, gypsum and Bagasse wood, recycled aluminum, double laminated glass with insulation using Low-E glass in the structural glazing and fenestrations, and zero VOC (volatile organic compounds) paints and adhesives;



HEALTHY ENVIRONMENT VAVs (variable air volumes) using non-ozone depleting R 410-A as the refrigerant gas, and ecofriendly housekeeping practices.



Other environmentally conscious elements include rain water harvesting and grey water systems as well as low-VOC protective coatings, paints and flooring materials from BMS.

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7.7. CLIMATIC ANALYSIS 7.7.1 WEATHER DATA SUMMARY The building is located in Gurgaon, India beside New Delhi, which has the humid subtropical climate with high variation between summer and winter temperatures and precipitation. But New Delhi's noticeably different from many other cities with the same climate. It features long and very hot summers, relatively dry and cool winters, and monsoon and dust storms. More specifically, summer is from early April to October while winter starts in November and peaks in January. As shown in the table 7.2, January has the lowest ‘average temperature’ which is 14.1 °C (57.4 °F). On the other hand, the highest ‘average temperature’ is in the June (33.8 °C (92.8 °F)).

Table 7.7. 24-hr Average Temperature of New Delhi

7.7.2 AVERAGE AND RECORD HIGH AND LOW TEMPERATURE As shown in the table 7.3, the highest ‘average high temperature’ is in the May, which is 39°C (102°F) while the lowest ‘average temperature’ is in the January, which is 7°C (45°F). In terms of record temperature, the highest ‘record high temperature’ is 47°C (117°F) in May and July and the lowest ‘record low temperature’ is -1°C (30°F) in January.

Table 7.8. Climate Data for New Delhi

7.7.3 PRECIPITATION Table 7.4 is the average rainfall data in New Delhi. The overall Average Rainfall during the whole year is 706.4 mm (27.8 inches). From June to October some areas facing the sea, rainfall can be very heavy indeed. In July and August, the average rainfall reaches the biggest which is 200.4 (7.9 inches) and 200.3 (7.9 inches), respectively. But, there is only 3.0 mm (0.1 inches) in November.

Table 7.9. Average Rainfall in New Delhi

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7.8. IMPLEMENTATION OF ENERGY SIMULATION 7.8.1. e-QUEST ENERGY ANALYSIS The projects have been modeled using the e-QUEST energy analysis software. E-QUEST uses the DOE 2.1 Building energy simulation engine. It has the ability to explicitly model all of the following:

 

8,760 hours per year

  

Thermal mass effects

Figure 7.15. 3D View Showing Graphic Rendering of Model using eQUEST

7.8.2. SIMULATIN RESULTS BASECASE ENERGY CONSUMPTION The Basecase model is based upon the proposed design, but the performance parameters listed are defined to reflect the minimum efficiency levels that ASHRAE 90.1-2004 defines for various building components. Detailed input parameters are listed at the end of this report. Based on the energy simulation results, it is observed that the averaged Basecase building consumes a total of 1268148 kWh/yr at an Energy Use Index (EUI) of 13 kWh/sqft/yr. The primary energy end-uses are cooling (41%), followed by equipment (29%), lighting (17%) and space heating (6%) as illustrated by the following charts.

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Figure 7.17. Energy-use Characterization Basecase (1000 kWh, %)

Figure 7.16. Energy-use comparison for all End uses Basecase (1000 kWh)

Detailed investigation into the result suggests that Internal loads (51%) form the largest component of HVAC requirement followed by Envelope loads (26%). The results are as-expected for the project climate (Composite) and building type (commercial).

DESIGN CASE ENERGY CONSUMPTION In accordance with the above breakdown, the design Case incorporates High efficient HVAC System and an efficient lighting system (31% better than basecase). These two strategies offer the biggest potential for energy savings. Additional savings are achieved by reducing fresh air loads by incorporating strategies like demand controlled ventilation and exhaust air energy recovery. Detailed performance parameters for the Design case are listed at the end of this report. Overall, the Design case shows an EUI of 9kWh/sqft/yr achieving energy savings of 32% over basecase, primarily owing to a 60% savings in Cooling and 40% savings in Fan energy. ENERGY COST COMPARISON The design case shows annual utility cost savings of 32% over the basecase. The table below lists the costs related parameters. Additionally, on-site photovoltaic array would generate 100,000 kWh of annual electricity reducing the design case energy costs by Rs.5,00,000 which increases the energy cost savings to 39.89% over the basecase. Based on these results, the project should achieve Nine (9) points under IGBC LEED NC EAc1.

Figure 7.18. Energy Use comparison for all End Uses Basecase vs Design case (1000 kWh)

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FUEL TYPE

BASE CASE

DESIGN CASE

Electricity

63,34,000.0

43,07,500.0

Total

63,34,000.0

43,07,500.0

DETAILED ENERGY MODEL INPUT PARAMETERS

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7.9. IDENTIFICATION OF DESIGN PARAMETERS 7.9.1. BASIC DESIGN PARAMETERS The basic design parameters considered while analyzing the energy simulation methods are mentioned below :

  



SITE LOCATION GEOGRAPHIC LOCATION ALTITUDE

Gurgaon, Haryana 28.58 deg N; 77.20 deg E 216 m above mean sea level

Summer

107 Degree F :(41.8 Degree C) DB

74.48 Degree F :(23.6 Degree C) WB

Monsoon

91.94 Degree F :(33.3 Degree C) DB

83.12 Degree F :(28.4 Degree C)WB

Winter

42.80 Degree F :(6.0 Degree C) DB

41.36 Degree F :(5.2 Degree C)WB

BUILDING AREAS FLOOR



CONDITIONED AREA (SQ. FT)

GROSS BUILT UP AREA (SQ. FT.)

Basement

0.00

25,184

Ground Floor

19,096

21,652

First Floor

19,184

22,194

Second Floor

19,218

22,194

Third Floor

15,501

18,229

Total

72,999

109,453

BUILDING OPERATION SCHEDULES

Figure 7.19. Profile showing Loads of Interior & ExteriorLighting, Equipment, Occupancy, Elevator & Pumps

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

TEMPERATURE PROFILE

Figure 7.20. Comparison of Heating and Cooling Temperature Profiles



FAN SCHEDULE

Figure 7.21. Graph showing Fan Schedule

7.9.2. ENVELOPE DETAILS



WALL ASSEMBLY 200mm thk AAC Block with 12mm Plaster on both the faces. (Assembly U-value – 0.109 Btu/hrft² Degree F)

Figure 7.22. Section of External Wall

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

ROOF ASSEMBLY 200mm thk RCC slab + 75mm extruded polystyrene + 100mm screed + 10mm thk china mosaic tile. (Assembly U-Value – 0.057 Btu/hrft2 Degree F)



WINDOW FRAME CONDUCTANCE FOR BASECASE The frames are unlabeled and an area weighted frame width of 1.3 inches for each window is calculated for the Design model. The frame conductance considered for evaluation is 1.8 Btu/h-sqft-DegreeF based on Aluminum Frame without thermal break, fixed double glazed windows.

Figure 7.23. Section of Roof

7.9.3. LIGHTING DETAILS

Table 7.10. Lighting Details of Ground and First Floor of Delta Electronics Pvt ltd.

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Table 7.11. Lighting Details of Second, Third and Basement Floors of Delta Electronics Pvt ltd.

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7.10. SIMULATION OUTPUT SUMMARY 7.10.1. UNMET HOURS FOR PROPOSED CASE :

7.10.2. UNMET HOURS FOR BASECASE :

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7.10.3. ENERGY COST SUMMARY FOR PROPOSED CASE :

7.10.4. ENERGY COST SUMMARY FOR BASECASE :

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CHAPTER 8

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8.1. OVERVIEW Buildings consume energy and various resources in all stages of their life cycle : various materials used in construction, the construction procedure and during operation for providing comfort conditions for the occupants. Buildings are responsible for at least 40% of energy use in most countries and this produces the need for reduced energy consumption upto acceptable levels of comfort, air quality and other occupancy requirements in Building Design. One of the major areas to cut down this energy consumption is the Building Envelope which consumes around 26% of the total energy requirement of a building, where 17% of energy savings in this area can be easily achieved by maintaining some recommendations for Building Envelope Optimization (26% savings in HVAC, 14% in Plug Loads, 4% in Water Heating). Hence a good envelope design should be the result of a systematic approach, checking all relevant elements. A new approach to consider the building and the envelope quality is the "Performance Concept". The performance of an envelope includes all aesthetic and physical properties to be fulfilled by that envelope, integrated into the function of the building as a whole.

8.2. ENERGY EFFICIENCY IN BUILDINGS Energy analysis is an integral component of sustainable building practices. There are three main approaches for Energy Efficient Building Design :

  

Cut buildings’ energy demand by, for example, using equipment that is more energy efficient Produce energy locally from renewable and otherwise wasted energy resources Share energy – create buildings that can generate surplus energy and feed it into an intelligent grid infrastructure.

Because of the increased emissions of wastes and the depletion of fossil fuels, research and development in building technologies and integrated design processes have attained greater and renewed interest among stakeholders worldwide. Hence proper benchmark and design thumb rules should be achieved for making buildings Energy Efficient or in other words sustainable, especially in commercial sector as commercial buildings account for almost 39% of total energy consumption and 38% of carbon dioxide (CO2) emissions.

8.3. OPTIMIZATION OF BUILDING ENVELOPE DESIGN The building envelope refers to the exterior façade, and is comprised of opaque components (Walls, roofs, slabs on grade (in touch with ground), basement walls, opaque doors) and fenestration systems (Windows, skylights, ventilators, and doors that are more than one-half glazed). The building envelope directly influences the energy performance of a building in the following ways:

      

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Energy Efficiency in Building Envelope design can be achieved in two ways : By isolating the interior of the building from the external environment using insulations or by adopting Passive Design approaches which reduces the energy requirement of the mechanical systems.

8.4. PARAMETERS AFFECTING ENERGY PERFORMACE IN BUILDINGS Performance Assessment of Office Buildings is necessary to achieve an energy efficiency level of greater than 50% toward a net zero building from ASHRAE/IESNA Standard 90.1-2004 (ASHRAE 2004). No single discipline alone can apply sufficient measures to achieve this level of energy efficiency. Hence the following design parameters must be introduced in order to achieve the above mentioned energy savings :

BUILDING ENVELOPE COMPONENTS

PARAMETER 1

PARAMETER 2

Exterior Opaque Surfaces

Heat Capacity

U-factor

Fenestration

U-factor

Solar Heat Gain Coefficient (SHGC)

Figure 8.1. Parameters influencing Building Envelope Design

Building Envelope Design should also cater to the occupant health and comfort covering the following aspects : INDOOR AIR QUALITY (IAQ) Must not be compromised in order to reduce the energy consumption of a building. The following key objectives must be followed in order to provide adequate IAQ inside a building :

  

Manage the design and construction process to achieve good IAQ Control moisture in building assemblies Limit entry of outdoor contaminants

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    

Control moisture and contaminants related to mechanical systems Limit contaminants from indoor sources Capture and exhaust contaminants from building equipment and activities Reduce contaminant concentrations through ventilation, filtration, and air cleaning Apply more advanced ventilation approaches

THERMAL COMFORT Should be maintained by determining the normal activity level of the occupants in each main zone covering the main concepts of dry-bulb temperature, relative humidity and operative/“effective comfort” temperature which may vary due to seasonal changes and climate zones. For example, in zones facing the equator (south in the northern hemisphere), the low sun angle significantly increases the penetration of direct sunlight into the building. The perceived temperature can change significantly throughout the day due to direct sunlight falling on occupants. Typical considerations for thermal comfort include :

     

Metabolic rate, Clothing insulation, Air temperature, Radiant temperature, Air speed, Humidity

VISUAL COMFORT Lighting, both daylight and electric light if designed and integrated properly, will minimize visual comfort issues in the space. Orientation to windows is also very important in minimizing discomfort issues. Computer screens should never be positioned facing windows or facing directly away from the window. Both of these situations produce very high contrast ratios, which cause eye strain. ACOUSTIC COMFORT The building design should also cover ambient noise criteria for each space, acoustic privacy, occupant-created background noise, and speech intelligibility.

8.5. ADVANTAGES OF ENERGY SIMULATION IN BUILDING ENVELOPE DESIGN Energy Simulation softwares simulate the energy required in a building at the conceptual design level based on the approximate footprint of the building using real time data and weather conditions of that particular place. This process also gives the measure of the energy that will be consumed in the building as per various national and international standards. Thus it helps to set a benchmark level of energy consumption for a particular type of building. The report gives an overview of eQUEST which is a DOE.2 based free building energy analysis simulation program widely used for LEED projects. The main advantages of eQUEST are listed below :



eQuest calculates hour by hour building energy consumption over an entire year (8,760 hours) using hourly weather data for the location under consideration.



eQuest also contains a dynamic daylighting model to assess the effect of natural lighting on thermal and lighting demands.

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

The simulation process begins by developing a “model” of the building based on building plans and specifications which can also be developed by importing AutoCad Drawings into eQuest.



A base line building model that assumes a minimum level of efficiency (e.g., minimally compliant with ASHRAE 90.1) is then developed to provide the base from which energy savings are estimated.



These results are shown in the form of Graphical Reports such as : 1. Single Run Report on Monthly Energy Consumption by End Use 2. Single Run Report on Annual Energy Consumption by End Use 3. Single Run Report on Monthly Peak Demand on End Use 4. Single Run Report on Annual Peak Demand by End Use 5. Single Run Report Showing Monthly Utility Bills 6. Comparison Report on Monthly Total Energy Consumption 7. Comparison Report of Annual Energy by End Use

8.6. DERIVING DESIGN THUMB RULES FOR OPTIMUM ENERGY EFFICIENT SOLUTIONS The following thumb rules for Building Envelope Optimization are derived from the case studies on a Net Zero Energy Small office Building : Eco Commercial Building, Greater Noida and a LEED Platinum rated Medium office Building : Delta Electronics India pvt. Ltd., Gurgaon. The Envelope design criterias to achieve an Energy Saving of upto 17% for office buildings located in any climate zone can be listed as under : RECOMMENDATIONS FOR ROOF DESIGN (Saves Around 5% of the Total Energy Consumption) Sl. No.

RECOMMENDATIONS FOR ROOF DESIGN

K VALUE Btu/hr.ft2-Degree F

R VALUE hr.ft2-Degree F/Btu

210

0.00

0.035

8.10

0.9 mm Thick roof

50 mm Mineral wool Insulation

GI Wire mesh

0.001

65 x 65 mm MS Box section - PURLIN

0.033

25 mm Thick screed

0.41

0.346

75 mm Thick Fly ash coba

0.03

3.12

75 mm Thick PIR Insulation-LLOYD (On slab)

0.021

20.25

2 mm PUR BAYTECH water proof coating

0.2

2.13

150 mm RCC slab

0.43

Total -R value

34.13

Total -U value

0.032

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RECOMMENDATIONS FOR WALL DESIGN (Saves Around 8% of the Total Energy Consumption) Sl. No.

RECOMMENDATIONS FOR WALL DESIGN

K VALUE Btu/hr.ft2-Degree F

R VALUE hr.ft2-Degree F/Btu

0.036

3.94

25 mm Thick skirting-Kota stone

18 mm Thick internal plaster

0.9

0.113

150 mm Thick Flyash masonry

0.03

6.24

25 mm Thick external plaster

0.9

0.158

2 mm PUR BAYTECH water proof coating

0.17

0.067

150 mm Thick PIR insulation-LLOYD

0.021

38.00

2 mm PUR BAYTECH water proof coating

0.17

0.067

57 mm Air cavity

0.24

13.47

16 mm Thick FAVETON Tiles

0.22

0.41

Total -R value

62.46

Total -U value

0.016

RECOMMENDATIONS FOR FENESTRATION DESIGN (Saves Around 8% of the Total Energy Consumption) Glazing Type : Uvalue of Glazing : Solar heat Gain Coefficient : Window Wall Ratio(WWR) : Visible Light Transmittance : Frame Width : U-value of Frame :

Double Glazed Window 0.31 Btu/hr-sqft-Degree F 0.35 30% 50% 1.3 Inches 1.8 Btu/hr-sqft-Degree F

8.7. FUTURE SCOPE OF RESEARCH WORK The performance assessment procedure has been applied specifically to the design of building envelopes and has been shown to provide valuable insights in relation to both traditional envelope design and advanced envelopes based on specific climate zones and conditions. Having demonstrated the value of an integrated approach, the aim should be to apply the methodology more widely in order to reduce the energy consumption in Building Industry and hence the main focus of every building design should be energy efficiency and sustainability in order to proceed towards the concept of Zero-emission Building.

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REFERENCES UNPUBLISHED THESES 1. ENERGY PERFORMANCE OF BUILDING ENVELOPE AND ITS IMPACT PRESENTED BY : T.S. Deepak, 2006 2. APPROACH TO TOTAL BUILDING PERFORMANCE PRESENTED BY : Neha Prakash, 2008 3. APPLICATION OF ENERGY SIMULATION IN GREEN BUILDING PLANNING & DESIGN PRESENTED BY : Taniya Sanyal, 2008

PUBLISHED BOOKS 4. MANUAL OF TROPICAL HOUSING AND BUILDING Koenigsberger, Orient Longman 5. ENERGY EFFICIENCY IN BUILDINGS CIBSE Guide F 6. ENERGY MANAGEMENT IN BUILDINGS, 2ND EDITION Keith J. Moss 7. ENERGY SIMULATION IN BUILDING DESIGN, 2ND EDITION J. A. Clarke (Professor of Environmental Engineering University of Strathclyde Glasgow, Scotland)

CODES & STANDARDS 8. ASHRAE STANDARD 90.1 – 2010 Code for Commercial buildings (including multi-family high-rise buildings) 9. ENERGY CONSERVATION & BUILDING CODE – 2007 Energy conservation code for Residential and Commercial buildings based on climatic zones 10. ADVANCED ENERGY DESIGN GUIDE FOR SMALL TO MEDIUM OFFICE BUILDINGS– 2011 American Society of Heating, Refrigerating and Air-Conditioning Engineers The American Institute of Architects Illuminating Engineering Society of North America U.S. Green Building Council, U.S. Department of Energy 11. COMMERCIAL ENERGY CONSERVATION CODE – 2008 Based on ANSI/ASHRAE/IESNA Standard 90.1-2004 (Includes ANSI/ASHRAE/IESNA Addenda listed in Appendix F)

JOURNALS & PAPERS 12. ENERGY EFFICIENT BUILDING ENVELOPE DESIGNS FOR COMMERCIAL BUILDINGS Izael Da Silva; Edward Baleke Ssekulim, Strathmore University, Centre for Research in Renewable Energy and Sustainable Development, Nairobi-Kenya 13. BUILDING ENVELOPE OPTIMIZATION USING EMERGY ANALYSIS Ravi S. Srinivasan, William W. Braham, Daniel E. Campbell, D. Charlie Curcija

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Windows and Daylighting Group, Lawrence Berkeley National Laboratory, Berkeley CA 14. INTEGRAL BUILDING ENVELOPE PERFORMANCE ASSESSMENT Technical Synthesis Report IEA ECBCS Annex 32 15. INTELLIGENT BUILDING ENVELOPES ARCHITECTURAL CONCEPT & APPLICATIONS FOR DAYLIGHTING QUALITY Doctoral thesis for the degree of doktor ingeniør, Trondheim, November 2005, Norwegian University of Science and Technology 16. CONTRASTING THE CAPABILITIES OF BUILDING ENERGY PERFORMANCE SIMULATION PROGRAMS Drury B. Crawley, U.S. Department of Energy, Washington DC, USA Jon W. Hand, Energy Systems Research Unit, University of Strathclyde, Scotland UK 17. EFFECTIVE USE OF BUILDING ENERGY SIMULATION FOR ENHANCING BUILDING ENERGY CODES Sam C. M. Hui Department of Mechanical Engineering, The University of Hong Kong 18. ADVANCED ENERGY MODELING FOR LEED Technical Manual v2.0 September 2011 Edition

WEBSITES 19. http://www.wbdg.org/design/envelope.php 20. http://www.energydesignresources.com/technology/building-envelope-design.aspx 21. http://www.sustainablehouseplans.biz/climate-specific-envelope-design.html 22. http://www.hpo.bc.ca/building-envelope-guide-houses 23. http://ecocommercial-building-network.com/portfolio-view/zero-emissions-office-india/ 24. http://www.deltaelectronicsindia.com/green_building.aspx