ACHIEVING ENERGY EFFICIENCY IN EXISTING RESIDENTIAL BUILDINGS BY RETROFITTING BUILDING ENVELOPE

RESEARCH TOPIC:

ACHIEVING ENERGY EFFICIENCY IN EXISTING

RESIDENTIAL BUILDINGS BY RETROFITTING

BUILDING ENVELOPE IN COMPOSITE CLIMATE

DISSERTATION 2020

Final Report

Word Count: 10500

Name of Guide: Prof.Dr.Shweta Manchanda

Name of Coordinator: Prof. Dr. Jaya Kumar

Name of student: Milind karsoliya

Roll No.: A/2941/2016

Year and Section: 5TH Year & Section B

School of Planning and Architecture, Delhi

An “Institution of National Importance” Under an Act of Parliament (Ministry of Education, Govt. of India)

The research work embodied in this dissertation titled “ACHIEVING ENERGY EFFICIENCY IN EXISTING RESIDENTIAL BUILDINGS BY RETROFITTING BUILDING ENVELOPE IN COMPOSITE CLIMATE” has been carried out by the undersigned as part of the undergraduate Dissertation programme in the Department of Architecture, School of Planning and Architecture, New Delhi, under the supervision of Prof. Shweta Manchanda

The undersigned hereby declares that this is his original work and has not been plagiarised in part or full form from any source.

Signature of candidate

Name: Milind karsoliya

Roll No.: A/2941/16

Year and Section: 5th Year Sec B

Date: 02-12-2020

Acknowledgements

I take this opportunity to express my gratitude to several individuals, without their guidance and support this dissertation could not be possible…

Firstly, I would like to thanks my guide Prof. Shweta Manchanda for her patience and valuable inputs which gave me direction and motivation to execute this research.

I would also like to thanks my dissertation coordinator, Prof. Jaya Kumar for her encouragement and useful critique of the work.

A special thanks to the professionals in the field without whom my dissertation would not have been complete,

Sanjay Prakash, Principal consultant at SHIFT

Salil Mohan, Assistant Director at Delhi Development Authority(DDA)

Sameer Maithel, Greentech Knowledge Solutions Pvt. Ltd.

Gaurav shorey, Director at PSI Energy pvt. Ltd.

Deepa parekh, Sr. Project Manager, at Environmental design solutions

Prof. Shweta suhane, Assistant Professor at Nirma University

Lastly, I would like to express my gratitude to my Parents, my brother Vipin singh karasolia and my classmates for providing me constant support, motivation, and constructive time when I needed it the most.

Abstract

As we know, that buildings in India accounted for 31% of total energy consumption, in which residential buildings account for 23% of energy and the rest 8% is for commercial buildings. As recent research done by TERI also projected that Electricity consumed by buildings today is more than the electricity will be consumed by the buildings that will be constructed over the next 20 years. So research is required to control the energy consumption from the existing stock of residential buildings and this dissertation revolves around identifying retrofitting building envelope strategies for existing residential buildings to achieve energy efficiency with focussing on composite climate.

The methodology followed in this research. (1) Secondary analysis of existing literature (BEEP design guidelines, Eco Niwas Samhita, and green building initiatives for accordable housing by TERI) to extract strategies that can be used for retrofitting the building envelope of existing residential buildings. (2) A qualitative Questionnaire survey to the Architects, building energy consultants, and Academician is done to know the current practice of energy efficiency strategies in Residential buildings. Then Retrofitting Building envelope strategies are identified from a secondary and primary study, which mainly are adding insulation on Roof and wall, Adding overhangs on windows, changing fenestrations from single glazing to double glazing, adding solar reflective tiles and paints on walls and roof, etc.

Buildings simulation was done on a Middle-income housing project in Indore (composite climate) using the Eco-niwas Samhita analytical tool. Building simulation is done on the selected bedroom (southeast façade) and living room (southwest façade) of different clusters. Energy performance index (EPI) and residential envelope transmittance value(RETV) is calculated. Since RETV is calculated then the efficiency of the building envelope can be predicted irrespective of simulation of other orientations because the lower the RETV value means the envelope is more energy efficient.

Results of the simulation indicated that the energy efficiency of a maximum of 53% for bedrooms on the intermediate floor and 51% for the living room on the intermediate floor is possible. Similarly, building simulation done on the top floor case for both the bedroom and living room indicated that the energy efficiency of a maximum of 55 % for the bedroom and 51 % for the living room is possible.

Keywords; Energy efficiency, Retrofitting, Residential buildings, Building Envelope, RETV

List of Figures

Fig 1: Sector-wise energy consumption in India

Fig 2: Building stock energy consumption in India

Fig 3: Existing building stock vs. new building stock energy projection

Fig 4: Residential building energy consumption breakup

Fig 5: Road map for retrofitting existing buildings.

Fig 6: Methodology of energy efficiency design guidelines

Fig 7: Schematic of a base case

Fig 8: Schematic of packages measure I

Fig 9: Schematic of packages measure II

Fig 10: Schematic of packages measure III

Fig 11: Comparison of all packages of measures with base case

Fig 12: Steps for checking compliances for composite climate

Fig 13: Site Plan DB PRIDES

Fig 14: Cluster plan of type C3

Fig 15: Steps for checking compliances for composite climate

Fig 16: Dwelling plan of type C3 (OPTION 1)

Fig 17: Dwelling plan of type C3 (OPTION 2)

Fig 18: Methodology for simulation

Fig 19: Schematic of Bedroom base case for simulation

Fig 20: Base case Simulation Result of Bedroom at intermediate floor

Fig 21: Strategy 1 Simulation Result of Bedroom at intermediate floor

Fig 22: Strategy 2 Simulation Result of Bedroom at intermediate floor

Fig 23: Comparison of RETV of all the strategies with base case

Fig 24: Comparison of EPI of all the strategies with base case

Fig 25: Base case Simulation Result of Bedroom at top floor

Fig 26: Strategy 1 Simulation Result of Bedroom at top floor

Fig 27: Strategy 2 Simulation Result of Bedroom at top floor

Fig 28: Strategy 3 Simulation Result of Bedroom at Top floor

Fig 29: Comparison of RETV of all the strategies with base case

Fig 30: Comparison of EPI of all the strategies with base case

Fig 31: Schematic of Living room base case for simulation

Fig 32: Base case Simulation Result of intermediate floor living room

Fig 33: Building Simulation Result after applying strategy 1 of intermediate floor living room

Fig 34: Building Simulation Result after applying strategy 2 of intermediate floor living room

Fig 35: Comparison of RETV of all the strategies with base case

Fig 36: Comparison of EPI % of all the strategies with base case

Fig 37: Comparison of RETV of all the strategies with base case for living room

Fig 38: Comparison of EPI % of all the strategies with base case for living room

List of Tables

Table 1: Vernacular green building strategies

Table 2: materials used in composite climate as green building materials

Table 3: Layer of external Wall

Table 4: Layer of Roof

Table 5: Layer of wall

Table 6: Summary of green building features

Table 7: minimum Window to floor area ratio

Table 8: minimum Window to wall area ratio

Table 9: coefficient of RETV calculation

Table 10: Thermal properties of building and insulating materials

Table 11: Proposed Building Envelope strategies

Table 12: Base case Building Envelope Inputs

Table 13: Building Envelope Strategies for bedroom at intermediate floor

Table 14: Building Envelope Strategies for bedroom at top floor

Table 15: Building Envelope Strategies for living room at intermediate floor

Table 16: Building Envelope Strategies for living room at top floor

Chapter 1: Introduction

1.1 Need for the study

Globally, buildings use about 40% of energy, and in the process, emit approximately 1/3rd of GHG emissions (UNEP, SBCI 2009). In India, buildings accounted for 31% of the total electricity consumption in the year 2014-15, second only after industries(Jaboyedoff et al., 2014). Of this residential buildings and commercial buildings account for ~23% and ~8%, respectively (AAYOG, 2017). Electricity consumption in residential buildings is about 2.3times more than that of commercial buildings. Where the residential sector has seen a near consistent growth of 9.57% in electricity demand from 1947-50 to 2015-17, the concurrent values for the commercial sector is 7.69% (TERI, 2019)

According to an estimate, electricity consumed annually by existing buildings today is more than the total electricity consumed by all buildings that will be constructed over the next 20 years (fig.3). (TERI, 2019).

Figure 1 SECTOR WISE ENERGY CONSUMPTION IN INDIA SOURCE- (Aayog 2017)

Figure 2 BUILDING STOCK ENERGY CONSUMPTION IN INDIA SOURCE- (Aayog 2017)

Figure 3 EXISTING BUILDING STOCK VS NEW BUILDING STOCK ENERGY PROJECTION SOURCE- (TERI 2019)

Although the government of India has initiated energy conservation codes(eco- Niwas Samhita) and BEEP design guidelines to improve the energy consumption from the new construction of residential buildings. Research is required to control energy consumption and enhance the energy-saving potential from the existing residential buildings. The executions of energy retrofit measures for expanding the energy proficiency of the existing buildings have been appeared to significantly affect lessening the energy consumption(Alam, Patrick X.W. Zou, et al., 2016) in developing countries like CHINA, US, AND UK. Retrofitting existing buildings can lead up to 15-20 % savings over the benchmark energy consumption. (TERI, 2019).

Energy efficiency in an existing building can be achieved by retrofitting the building envelope, HVAC, lighting system, electrical system, internal equipment. But building envelope remains an important parameter because Heat gains from the envelope play the most significant role in influencing thermal comfort and consequently energy efficiency in residential buildings(Jaboyedoff et al., 2014). Residential buildings have a large exposed façade area to built-up area ratio, resulting in the space cooling loads dominated by heat gains from the envelope(Jaboyedoff et al., 2014). According to a recent research “Heat balance of a building in India reveals that at least 20 to 30 % of the heat input into a building is through walls and roof “(SHANDILYA, Apeksha et al., 2017).

Building envelope

The building envelope is the skin of a building which consists of a wall, roof, and fenestration. The design of the building envelope influences heat gain/loss, natural ventilation, and daylighting, which in turn determines indoor temperature, thermal comfort, and sensible cooling/ heating demand(BEE, 2018). The retrofitting process of the building

Figure 4 RESIDENTIAL BUILDING ENERGY CONSUMPTION BREAKUP. SOURCE – BEE (2014)

envelope includes important measures such as external walls‟ insulation, windows‟ glazing type, airtightness (infiltration), and solar shading(El-Darwish and Gomaa, 2017).

1.2 Research Question

How Retrofitting building envelope can help in achieving energy efficiency in existing residential buildings?

1.3 Aim

To understand how retrofitting building envelopes of existing residential buildings can make it energy efficient.

1.4 Objectives

1. To identify the need for energy efficiency in existing residential buildings.

2. To evaluate the current energy efficiency codes and guidelines i.e. Eco-Niwas, BEEP design guidelines for multi-storey buildings, and green buildings initiatives for affordable housing for HUDCO.

3. To identify retrofitting building envelope strategies that can help reducing energy consumption in existing residential buildings.

4. Building simulation of the identified base case and after adding some possible building envelope retrofit features that can reduce energy consumption.

5. To compare and showcase certain possible retrofit building envelope options.

1.5 Scope

1. This Dissertation's immediate scope is concerned with establishing the role of the building envelope in turning existing residential buildings into energy-efficient residential buildings.

2. Evaluation of the current energy efficiency code falls under the scope of the dissertation.

3. This dissertation scope is limited to multifamily Middle-income Group housing in the composite climate zone.

1.6 Limitations

1. Because the study is performed in the COVID-19 period hence only virtual interaction and questionnaire through online mode was possible.

2. The study is performed using building simulation software to measure the energy consumption of buildings.

Chapter 2: Literature review

2.1 Introduction to global energy consumption scenario

In developed countries, the share of energy consumption of residential and commercial buildings is between 20% and 40% of total energy consumption (Pe´rezLombard et al., 2007). In the case of India, 31% of the total energy consumption of the nation is contributed by the existing building sector (Aayog 2017). The share of electricity consumption from the residential and commercial sectors are 23% and 8% respectively (CEA 2010).

A major part of the building stocks existing today was built before the introduction of sustainability benchmarks and is energy inefficient(Alam, Patrick X W Zou, et al., 2016). Governments around the world have taken strong measures towards the retrofit of existing buildings in terms of improving energy performance and mitigating GHG emissions (Alam et al. 2016) According to a recent research “Heat balance of a building in India reveals that at least 20 to 30 % of the heat input into a building is through walls and roof “(Shandilya, Apeksha et al., 2017).

Energy consumption due to space conditioning varies depending on climate zones and age of home because besides the HVAC system, envelope systems are also responsible for the level of energy consumed for space conditioning (kamel & Memari 2016). about 25% to 35% of energy for space conditioning is wasted due to inefficient window systems (Oldfield et al. 2015).

In any building, the building envelope plays an important role as It does not consume energy but affects the energy usage from a mechanical appliance by cooling and heating loads. The building envelope is the physical boundary that separates the habitable areas from the external environment(Far and Far, 2019). The building envelope consists of walls, fenestration, roof, foundation, thermal insulation, thermal mass, external shading devices(Wang et al., 2009).

2.2 Building envelope strategies for new construction

In (BEE 2014) they have given three packages of building envelope interventions to minimize the energy consumption in multi-storeyed residential buildings.

Package I

The package I comprise of arrangements that are economically accessible and are now being implemented in a portion of the multi-story buildings

Use of light colors on external walls (absorptivity ≤0.4): Surfaces having higher absorptivity absorbs a larger fraction of the solar radiation incident on them. By using light color finishes/paints on the exterior surfaces of the external wall, a lower absorptivity of around 0.4 can be obtained. (BEE 2014)

 Window shades with extended overhangs: The overhang on top of the window lintel is extended sideways on both sides by 0.5 m and This extension helps in cutting the solar radiation falling on the window. (BEE 2014)

 Insulated walls (U-value: 0.7 W/m2.K): A typical 9-inch (230 mm) brick wall has a U-value of around 2.0 W/m2.K. If the U-value for the external walls is reduced, then the heat transmission due to conduction through external walls can be reduced. A Uvalue of around 0.7 W/m2.K can be achieved by using a 200-mm thick autoclaved aerated concrete (AAC) block or 200-mm thick hollow concrete or fired clay blocks filled with insulation materials, or a combination of 230-mm brick wall along with suitable insulation thickness. (BEE 2014)

 Optimised natural ventilation: This strategy considers the opening of 50% of the effective window area to facilitate natural ventilation whenever the outside temperature is ≥2 °C cooler than the indoor temperature. (BEE 2014)

Package II

Package II consists of measures suggested in Package I, along with the addition of external movable window shutters. (BEE 2014)

Package III

Package III is an improvement over Package II. In addition to the measures described in Packages I and II, the configuration are the following:

 Insulated walls (U-value: 0.5 W/m2.K): Use of better insulated walls4 to achieve Uvalue 0.5 W/m2.K. This can be achieved by a cavity wall with about 50 mm of modern insulation materials. (BEE 2014)

 Double-glazed windows: Use of double clear glazing on windows with the following properties (U-value: 2.8 W/m2.K, SHGC: 0.75). (BEE 2014)

 Better building tightness: Infiltration losses from the building envelope can be reduced to ~0.35 ACH by improving building air-tightness. This is achieved by effectively sealing the joints in the building envelope components by using caulks, gaskets, and weather strips. (BEE 2014)

3 Retrofitting building envelope strategies

Retrofitting building envelope strategies recommended by (Jha & Bhattacharjee 2018) are

 Adding insulation material to the roof and wall. insulation material of the thermal resistance (R-values) between 0.90 and 2.3 m2 _C/W for wall and roof sections respectively are recommended. (Jha & Bhattacharjee 2018)

 Airtightness and infiltration, normal movement of air from inside to outside or viceversa is air leakage. According to a study reducing air, leakage can save 5–40% of heating and cooling energy (OECD/IEA). Air leakage can be reduced by using sealants, gaskets, and additional window panels. (Jha & Bhattacharjee 2018)

 Window glazing, Windows have functions such as providing daylight, offers security, and heat flow. That‟s why appropriate size, orientation, and glazing is needed. Heat flow depends on the climatic condition. For example, a low U-factor (less heat loss) is most important in a cold climate; a low SHGC (less solar heat gain) is a priority where overheating is a concern and Visible transmittance is important when daylight is incorporated into the project design. (Jha & Bhattacharjee 2018)

 Solar shading, the use of solar shading devices can be helpful in making a building energy efficient. Solar shading devices restrict the direct light falling on fenestration to lower the energy demand for cooling the building. Some of the solar shading devices are, external overhangs (fins), horizontal reflecting surfaces (light shelves), low shading coefficient (SC) glass, interior glare control devices such as Venetian blinds or adjustable louvers, etc (Jha & Bhattacharjee 2018)

2.4 Challenges in retrofitting building envelope

Retrofitting existing buildings for energy efficiency is a big challenge because it involves Substantial funding and decision-making from a wide range of stakeholders such as landlords, tenants, property managers, developers, and the local council and Potential barriers against the uptake of energy-efficient retrofitting may arise from any stakeholder or group of stakeholders. (Alam et al. 2016)

2.5 Roadmap of retrofitting of existing buildings

Energy retrofit can be simply categorized into conventional and deep energy retrofit(Kamel and Memari, 2016). In conventional energy retrofit, usually simple and fast methods are used and different systems are considered separately and For deep energy retrofit, a wholebuilding retrofit approach is usually considered. (Zhai et al. 2011).

In India, The Energy and Resources Institute (TERI 2019) has identified six steps for energy efficiency retrofits in existing buildings:

Building energy simulation using (energy plus, equest, or firstrate5) after applying retrofitting strategies can be performed to get an estimate of how much saving potential and energy efficiency can be achieved. In recent research with the help of simulation, it was found that retrofit strategies such as solar shading can reduce energy up to 23% on average, followed by glazing strategy that reduced energy by 8% on average, and Airtightness had little effect in energy reduction on the study samples as it reduced energy only 2% on average. (Darwish & Gomaa 2017)

In a study by (Aste, N 2012) A reduction in primary energy consumption by 40% was achieved through improving the building envelope only, without intervention on HVAC plant, lights, or other technical systems. (Aste, N 2012)

Figure 5 ROAD MAP FOR RETROFITTING EXISTING BUILDINGS. SOURCE- (TERI 2019)

Chapter 3: Research Methodology

3.1 Research Methodology

1. Literature reviews and background study for the Identification of the research question.

2. Secondary analysis of the current energy guidelines (BEEP), ECBC-R codes, and Green building initiative for affordable housing by TERI for HUDCO is done to understand strategies that can be applied to existing buildings.

3. Primary study through open-ended questionnaire surveys to understand the current practice of retrofitting an existing building to make it energy efficient.

4. Formation of possible retrofitting building envelope strategies from secondary and primary study.

5. Building simulations will be carried out of the base case and after adding identified building envelope strategies.

6. A comparison of both the simulation cases and feasible retrofitting strategies will be presented.

3.2 Selection criteria of Case studies

The dissertation focuses on the identification of the retrofitting building envelope strategies hence Energy efficiency design guidelines (BEEP), ECO NIWAS Samhita (energy efficiency codes ), Green building initiatives for affordable housing will be studied as a secondary case study And the research question can only be obtained from what is currently happening in the field. So this will be done through a survey questionnaire with stakeholders in the field, which will be the primary study.

3.3 Research process through the diagram

Chapter 4: Case study

4.1 Secondary analysis study

Case study 1

Design guidelines For energy-efficient Multi-storey residential buildings in composite Climate

Design guidelines For energy-efficient Multi-storey residential buildings in composite Climate are a comprehensive set of guidelines for designing energy-efficient multi-story residential buildings that are done by the Indo-Swiss Building Energy Efficiency Project (BEEP). (BEEP) is a Bilateral cooperation project between India‟s Ministry of Power (MoP) and Switzerland‟s Federal Department of Foreign Affairs (FDFA) (BEE 2014)

The methodology followed by BEEP while forming these guidelines are shown in fig(6)

The Guidelines of energy-efficiency strategies are presented in six sections dealing With:

 Building massing,

 Spatial configuration,

 Building envelope

 Building space cooling,

 Common services,

 Integration of renewable energy

Figure 6 METHODOLOGY OF ENERGY EFFICIENCY DESIGN GUIDELINES SOURCE- (BEE 2014)

Since this dissertation focuses on retrofitting of building envelope hence only the building envelope part of this guidelines are studied in detail.

Building envelope

Building envelope features that have an impact on energy demand in a residential unit are

 Size and location of window openings

 Shading system for windows

 Window properties

 Insulation properties of the wall

 Insulation properties of the roof

 Colour and finish of exterior surfaces (walls and roofs)

 Natural ventilation

 Building air-tightness

Recommendations for Building Envelope

Guidelines have formulated three packages of measures for building envelope to control the cooling thermal energy demand and improve thermal comfort. This process was carried out with the help of building simulation where they took one base-case model(fig7) of the bedroom and developed it in building simulation software.

Figure 7 SCHEMATIC OF BASECASE

SOURCE- (BEE 2014)

Package of Measures I that can achieve 15%–20% decrease in cooling warm energy interest: Use of light tones on the wall (absorptivity ≤0.4) + window shades with extended overhangs to intercept direct solar radiation on the window + insulated walls (U-value: 0.7 W/m2.K) + optimised natural ventilation.

Package of Measures II can achieve a 40%–45% decreasing in cooling thermal energy interest: Package of Measures I + external movable shutters on windows.

Figure 8 SCHEMATIC OF PACKAGES MEASURE I SOURCE- (BEE 2014)

Package of Measures III that can achieve nearly 50%–60% decrease in cooling thermal energy: Package of Measures II + wall insulation of (U-value: 0.5 W/m2.K) + use of double glazing in windows + better envelope air-tightness.

Figure 9 SCHEMATIC OF PACKAGES MEASURE II

SOURCE- (BEE 2014)

Figure 10 SCHEMATIC OF PACKAGES MEASURE III

SOURCE- (BEE 2014)

Comparison of all the packages with a base case

Energy-efficient roof – The roof can reduce the cooling thermal energy demand and improve thermal comfort by providing over deck insulation and high reflectance on the roof to minimize heat ingress through the roof. See (fig 11)

Figure 11 COMPARISONS OF ALL PACKAGES OF MEASURES WITH BASECASE SOURCE- (BEE 2014)

Figure 11 Typical section of the roof showing overdeck insulation and reflective surface source- - (BEE 2014)

Case study 2

Green buildings initiatives for affordable housing for HUDCO

It is a study to document green buildings strategies on existing affordable housing projects. It is done to assess the benefits of affordable housing projects and useful in the replication of strategies for affordable housing. This study is funded by HSMI. it is a research and analysis wing of HUDCO. Information gathered in this research will serve as a recommendation for HUDCO in their affordable housing projects(TERI, 2014).

The research was conducted in two phases-

In phase 1

A literature review of existing research on green buildings was done and its linkages with case studies of Indian and abroad context was formulated.

In phase 2

It is consists of field studies, Documentation of green building initiatives in the residential sector was done in all climate zones. And then physical checks and verification including interactions with various stakeholders of affordable projects were conducted. This is research conducted in all five climate zones but this dissertation has a scope limited to a composite climate so only the composite climate covered in this document will be analyzed.

Case studies of composite climate green building strategies

Vernacular Green building strategies practices

Sl No Features Details

1. Aangan (courtyard) It is located at the lowest level for the rain to drain and not to enter other parts of the house.

It is a source of ventilation and light. It allows cool air to settle down which then spreads towards adjoining spaces.

2. Jaali It controls the airflow and allows diffused sunlight to penetrate inside the house.

It cut downs excess radiation and filters air while it enters the interior spaces

3. Openings

a) Large openings are seen on the façade having low sill levels generally on the southwest wall to capture heat

during winter, allows only fresh air to enter.

b) Vents are located close to the ceiling to remove the hot air.

c) Louvered doors and windows are adopted, which let cool air inside by maintaining enough privacy.

d) Skylights are used to remove hot air.

4 Chajja a) Chajja is a shading device. Which is usually located above windows and doors and it also protects from rain.

b) It obstructs direct radiation from hitting the wall by absorbing part of the heat and slows down the transmission of heat.

c) Provides shade and creates a cool atmosphere below, for the people.

5 Thick wall a) Wall thickness generally adopted in this climate zone is generally between 400mm to 600mm as thick walls have a good thermal impact on the indoor air condition.

b) Dressed stone masonry, brick, and mud are also used as a thick wall in this climate.

6. Vegetation

a) Trees are planted to ensure a cool atmosphere and it also acts as a buffer to restrict heat entering inside the house.

b) It also Improves the quality of air by evapo-transpiration by adding water vapor to the air and thus, reducing the temperature.

7. Waterbody a) It improves the quality of air and keeps surrounding cool and provides comfort in outdoor spaces.

8. Verandah a) Semi-open spaces present in most of the houses are known as verandah. Which acts as a buffer and prevents an excess of radiation from entering inside.

9. High ceilings a) High ceilings are incorporated in most buildings to allow maximum comfort level because of the high ceiling there is enough space for air to circulate.

10. Other climateresponsive features.

a) Generally, houses are located on a raised platform to prevent rainwater from entering inside.

b) Also, most of the streets of the place are narrow, with buildings on both sides, because it shades and also cool surroundings for pedestrians.

Table 1 Vernacular green building strategies Source: (BEE 2018)

Materials used in composite climate

Sl No MATERIALS DETAILS

1. Teak wood Teak or sagwaan wood is mostly used in Composite climate because it is hardwood, durable, and strong. It can withstand most climatic conditions.

2. Lime plaster Lime is mostly used because it allows buildings to breathe by absorbing and releasing moisture. And because it is light-colored, it reflects the heat and keeps the house cool inside.

3. Adobe blocks Adobe bricks are sun-dried bricks that are comprised of earth, clay, and straw.

It is resistant to fire, water, and enables a good impact on the thermal conditions of the building.

Field study in composite climate

Mahindra Life Spaces – Aura

It is located in Gurgaon, Haryana. It is an IGBC gold certificate building. It is built in 17.6 acres of land. The architect of this project is Rk associates. It is built on a site area of 17.6 acres and has a total no. of dwell units 895. It is a high rise apartment.

Green features at the building level

Passive Designing – Natural Lighting, Sun responsive – Self-shadowing layout, Shading of lower floor clusters by high rise structures, Solar Water Heating Efficient Water

Fixtures(TERI, 2014)

Materials used for building fabric

All the external walls of the project are provided with AAC block as prime material. The total cost of the wall is Rs 5295/Cu.mt and the U value 0.56. AAC block is the prime material for thermal performance in the project. The material is certified by ISI, GRIHA, and IGBC for its effectiveness as a green material. Also, the material has recycled content and has a lower embodied energy of 197MJ/Sq.m against 235 MJ/sq.m for a concrete block that is conventionally used.

Table 2 materials used in composite climate as green building materials

Source: (BEE 2018)

Field study – TERI university hostel

It is located in New Delhi and was constructed in the year 2008. It has a site area of 8153.6 sqm. It is G+4 stories high. The architect of the building is Sanjay mohe and the climate consultant is airtron consultant .

Green features incorporated in this project are



available materials





Details of Building Envelope features

The building plan is rectangular in form with north and south orientated. The Green building materials used in this project are given below.

Table 3 Layer of external Wall Source: (BEE 2018)

Envelope

Roof - The roof is constructed with RCC with brickbat Coba and outside layer with white tiles. The white tiles are known to have a high reflective index which reduces the amount of heat absorbed by the roof.

Wall – Detail of wall construction is given below

Table 4 Layer of Roof Source: (BEE 2018)

Table 5 Layer of wall Source: (BEE 2018)

Summary of green Building features for the composite climate zone

1. Building materials & Structural systems

Roof treatment shaded/insulate/reflective, shaded windows, jalis, Use of locally available materials like stabilized earth blocks, AAC blocks, stone.

Case study 3

Eco Niwas Samhita (Energy Conservation Building Code – Residential (ECBC-R) (Part I: Building Envelope)

Energy Conservation Building Code – Residential (ECBC-R) (Part I: Building Envelope) is a code that has prepared by the Bureau of Energy Efficiency to set the minimum building envelope performance to limit gain/loss and also to ensure adequate natural ventilation and daylighting potential and The code applies to all residential buildings and residential parts of „mixed land-use projects‟, both built on a plot area of ≥500 m2 and code also provides design flexibility in terms to innovate building envelope features to meet compliance(BEE, 2018).

These codes are prepared in a simple to apply format, where it only requires simple calculations taking inputs from architectural design drawings(BEE, 2018). Hence no simulation of the building is required while following these codes. These codes provide the following provisions.

 Building envelope (except the roof)-

1. The maximum value of Residential envelope transmittance value (RETV) for building envelope.

2. The maximum value of thermal transmittance of the building envelope (except the roof) for the cold climate zone.

 Roof- Maximum value of thermal transmittance of the roof.

Table 6 Summary of green building features Source: (BEE 2018)

 Minimum operable Window to floor area ratio (WFROP) to adequate natural ventilation.

 It provides Minimum Visible light transmittance (VLT) for non-opaque building envelope components to provide adequate daylight potential.

Minimum requirements of envelope features for composite climate are given in the table below

Minimum requirements of visible light transmittance for composite climate are given in the table below

The thermal transmittance of the roof shall comply with the maximum Uroof value of 1.2 W/m2.K(BEE, 2018)

Calculation of the Thermal Transmittance of Roof (Uroof) can be done by using equation 1.

1

Thermal Transmittance of Roof (Uroof)

Table 7 minimum Window to floor area ratio Source: (BEE 2018)

Table 8 minimum Window to wall area ratio Source: (BEE 2018)

Equation

Thermal transmittance of Roof (Uroof) Source: (BEE 2018)

Where,

Uroof : thermal transmittance of roof (W/m2.k)

Aroof : total area of the roof (m2)

Ui : thermal transmittance values of different roof construction (W/m2.k)

Ai : areas of different roof construction

Residential envelope transmittance value (RETV) for the building envelope (except the roof)

The RETV for the building envelope (except the roof) shall comply with the maximum RETV of 15 W/m2(BEE, 2018)

The RETV for the building envelope (except the roof) can be calculated using equation 2.

Equation 2 Residential envelope Transmittance value (RETV) Source: (BEE 2018)

Where,

Value of (a,b, and c) in equation 2 is given in table 6

Summary of Eco- niwas to check compliance with the buildings is as follows

To calculate the thermal transmittance (U-value) of roof and wall

Step-1 –calculation of thermal resistance® of each material layer, which is used in the building component ( roof or wall ),

R= ti / ki

Where,

Ri= thermal resistance of material layer i, m 2.k/w

ti = thickness of material layer i, m

ki = thermal conductivity of material layer i, W/(m.k)

Step-2 – calculate total thermal resistance, Rt, as follows

Table 9 coefficient of RETV calculation Source: (BEE 2018)

Figure 12 steps for checking compliances for composite climate SOURCE- (BEE 2018)

Where,

Step-3 – to calculate the thermal transmittance of a wall or roof assembly

U = 1/ Rt

Where, U is the overall heat transfer coefficient, W/(m2.k)

Typical thermal properties of commonly used building and insulating materials are given in Table 6

Table 10 Thermal properties of building and insulating materials Source: (BEE 2018)

4.1.3 Comparative analysis of secondary studies

SI. NO Building envelope feature

Design guidelines For energy-efficient

Multi-storey residential buildings in composite Climate

External wall – 20cm AAC with u value of 0.7 w/m2.k

Package 2

External wall – 20cm AAC with a u value of 0.7 w/m2.k

Package 3

External wall – cavity brick wall with 50 XPS insulation ( u value 0.5 w/m2.k)

Green buildings housing for

Option 1

External wall mortar, gypsum cement mortar, outside. (see

Option 2

External wall of PUF board mortar 8 mm emulsion paint sandstone dry

Rcc 150 mm thick with brickbat Coba (100mm), with over deck insulation, Reflective surface finish/paints on the outer surface, and the layer of cement plaster 15mm thk on the inner surface.

window shades with extended overhangs to intercept direct solar radiation on the window

Rcc 150 mm mortar (20mm), 2.27) on the 6mm thick

No shading were designed be shaded by

.

1. Wall Package 1

2. Roof

3. Shading device

4. Glazing

Double glazing in windows in Package 3

buildings initiatives for affordable for HUDCO

Eco Niwas Samhita (Energy Conservation Building

Code – Residential (ECBC-R) (Part I: Building Envelope)

wall

Fly ash block with a layer of cement gypsum plaster, plastic paint inside and mortar, water repellent paint, external air film (see table 2)

Details of the wall are not given in the code. But Residential envelope heat transmittance (RETV) which includes wall, doors, windows, ventilators are considered and it Shall be a maximum of 15 w/m2. See( equation 2)

wall

230 mm thick Brick wall with a layer board (50 mm), Brickwork 115 mm thick, mm thick, plasters inside with white paint on inner surface and layer of dry cladding. ( see table 3 )

mm thick with brickbat Coba (125mm), (20mm), white tiles 18mm thick (u value the outer surface, and the layer of plaster on the inner surface. (see table 4)

device on individual buildings. Cluster designed in a way that lower floor clusters can by high rise structures

Thermal transmittance (Uroof) should comply with 1.2 W/m2.k)

.

the visible light transmittance of non-opaque building envelope should be between 0.27 to 0.11 with WWR varying from 0 to 0.70 respectively. (See table 8 for detail).

Other details are not given separately it is included in RETV (which also includes transparent and translucent objects of the building envelope). And RETV Shall be a maximum of 15 w/m2

4.2 Primary study – survey questionnaire

In Primary survey – open-ended questions were asked to stakeholders in the field to know the Current practice of energy efficiency in residential buildings:

i. Architects –

a) SANJAY PRAKASH, Principal Consultant at Shift: Studio for Habitat Futures.

b) SALIL MOHAN, Assistant Director (Architecture) at Delhi Development Authority (DDA) and Part of the development team for Energy Conservation Building Code for Residential buildings, Eco-Niwas Samhita 2018.

ii. Building Energy Consultants –

a) SAMEER MAITHEL, Greentech Knowledge Solutions Pvt. Ltd.

b) GAURAV SHOREY, Director at PSI Energy Pvt. Ltd. And Visiting faculty at School of planning and architecture, new Delhi

c) DEEPA PAREKH, Sr. Project Manager, at Environmental design solutions LEED AP, ECBC Master Trainer and visiting faculty at CEPT university

iii. Academician –

a) PROF. SHWETA SUHANE, Assistant Professor at Nirma University

The questions were based on the main aspects related to the study. The Summary report of the survey is as follows:

1. Can retrofitting an existing residential building to achieve energy efficiency be a good solution?

Yes Retrofitting existing residential buildings to achieve energy efficiency can be a good solution but it depends on several factors

i. Current energy consumption

ii. Period it was designed and built-in.

iii. If it can be effectively retrofitted with minimum modifications.

2. Main challenges associated with retrofitting a building envelope in existing residential buildings (especially for Multi-storey) Some challenges may be

i. For multi-storey residences, users are different so it is difficult to convince all. And also one may do not know the old energy system installed, dates,

wire lines, etc. It becomes difficult to retrofit all without knowledge. Difficult to find old records and bring them all on the same page.

ii. For the sake of maintaining the uniformity of the façade, replacement of windows and adding shading on windows may have challenges. Adding external insulation on outside walls may not be possible; however, internal insulation can be added.

iii. Technology challenges; competence and skills; some strategies can be complex

iv. Orientation, cost and technical capacity for external insulation, etc.

v. Practically in terms of walls having conduiting and plumbing retrofitting may not be feasible to retrofit.

3. Construction strategies and methods that you apply to retrofit the building envelope of an existing residential building to make it energy efficient.

i. For existing buildings try to recycle materials for retrofitting shading systems for doors and windows, radiant cooling may be another solution for conventional air conditioning.

ii. Insulation on the roof and/or reflective paint or tiles; adding fixed/external shading on windows; replacing existing windows with double glazed windows; adding insulation on the walls (internal), etc.

4. Materials that can be used for retrofitting a building envelope to make it energy efficient

i. For existing buildings, solar reflective paints may be used for facades and especially roofs. Terrace garden and roof insulation are key to minimize heat gains through the terrace.

ii. Insulation can be of many types, PUF, XPS, EPS, mineral wool, etc.; similarly, there are various materials for window frames (uPVC, aluminum, wood); there are a large number of glazing options; many companies are making high SRI paints and tiles.

iii. External Insulation on roofs: XPS or EPS with weld mesh and wire mesh reinforced cladding plaster and sloped with broken white tiles finish.

External Insulation on walls: XPS or EPS with weld mesh and wire mesh reinforced cladding plaster and grit/stone.

External Shading by retrofitting lightweight metal or concrete pergola and external devices per windows.

Colour: the whiter the better.

Orientation: no windows on the west or east, lots of windows on the south (even breaking windows is fine if allowed)

5. Are these materials and material providers easily available? And Does retrofit the building envelope of an existing residential building requires skilled labor/ fabricators? If yes then how easily they are available?

 Yes, Materials and material providers are easily available

 Retrofitting the building envelope of an existing residential building is a complex process and requires skilled labour.

 Skilled labour is easily available in large cities but a bit more difficult in small towns

6. Impact of building life cycle and structural stability on the retrofitting process of existing residential buildings to make it energy efficient?

i. It depends on whether the structure is framed construction or load-bearing. However, the major focus may be on the fenestration design and retrofitting shading systems. The shading device is better if it's lighter in weight and thus would have little impact on existing structural strength.

ii. Most retrofitting solutions may not have an impact on structural stability. It is not uncommon to have a major retrofit in flats like a change of floors, pipes, windows, bathroom tiles, once the flats are 10-20 years old. If the energy-efficient retrofitting can be clubbed with the general retrofitting, it may be more attractive to a homeowner.

iii. Very old buildings or with the weak structure are not worth retrofitting.

7. Is cost one of the major barrier in retrofitting an existing building to achieve energy efficiency

 Yes, especially as the buyer is already living in the place and wouldn't like to invest more, suddenly.

 If one looks purely from a point of view of the economic payback period, most of the retrofitting options will look to be expensive (long pay-back periods). However, a more comprehensive view that takes into account the benefits related to improved thermal comfort, improved living conditions, better utilization of the space, etc. is needed to justify the investment.

8. Client's receptivity for retrofitting their residence to make it energy efficient?

Clients do not have knowledge about Energy efficiency measures. So if they are not communicated about energy efficiency they will not do it.

9. Scope of retrofitting an existing building to make it energy efficient in India.

Moderate scope. But there is significant scope particularly for roof treatment, window shading, and window replacement. It may be the next big thing. However, each case would be unique and would present its own set of opportunities and challenges. As architects, we may choose to retrofit buildings professionally to achieve energy efficiency. The same can begin with one's own office or residence.

Chapter 5: Identification of building envelope strategies

Building envelope strategies identified from the analysis of secondary and primary study are presented in the table and then will be used on an identified base case using building simulation software.

S.NO

Building envelope feature

1 External wall

Proposed Strategies

1. Adding Insulation on the internal surface of the walls

2. Solar Reflective Paints with Tiles

3. Colour the whiter the best

Proposed Materials

50mm XPS or EPS insulation on the internal surface of the wall with 15mm plaster

2 Roof

3 Window

1. Solar Reflective Paints

2. Insulation on roof XPS insulation on the roof with high SRI tiles of solar reflectance 0.95 and thermal immittance of 0.91

1. Double glass glazing

2. Low E value glass Double glazing

1. VLT – 0.75

2. SHGC- 0.57

3. U value – 1.8 W/m2k

4 Shading device Overhangs and fins on External surface of windows Overhang with lightweight metal or operable external shutter on windows

Table 11 Proposed Building Envelope strategies

Chapter 6: Building simulation

Chapter outline - In this chapter building simulation will be done using the ENS tool by applying identified building envelope strategies on an identified base case and then a comparison of both the cases will be done.

6.1 Identification of base case

Project Details

Project name DB PRIDE INDORE

Housing typology Middle-Income-Group

Total Units 1743 units

Total towers 13 towers

Height Stilt (S) + 10 to S+14

Dwelling types 2BHK (TYPE B)

3BHK (TYPE A,G,F)

2.5BHK (TYPE C)

SOURCE-

SOURCE- (BEE

Figure 13 Site Plan DB PRIDE Source- (Jaboyedoff et al., 2014)

Fig14. Cluster plan of type C3

(BEE 2018)

Fig15 Cluster plan type B

2018)

SOURCE- (Jaboyedoff et al., 2014)

SOURCE- (Jaboyedoff et al., 2014)

6.2 Methodology adopted for building simulation is referred from (Jaboyedoff et al., 2014)

1. Selection of Sample bedroom and living Room

For this situation

Bedroom and Living rooms are chosen as they are the most utilized spaces, with the greatest inhabitance in nights and evenings. They are likewise spaces where air conditioners are destined to be introduced. Bedrooms and living rooms were chosen dependent on their orientation. In this case, the living room (southwest façade ) and bedrooms(southeast façade) are selected.

2. Base Case Simulation – Energy simulation of the sample bedrooms were developed in the ENS web tool. Inputs of the existing envelope features were entered, the simulation is carried out to predict the Energy performance index (EPI) and RETV of bedrooms and living rooms in an annual year.

3. Simulation After applying proposed Building envelope strategies- Building Envelope strategies are applied on sample bedroom (southwest façade) and living room (southeast façade) of the base case. Simulation done predicts the Energy performance index (EPI) and RETV of bedrooms and living rooms in an annual year.

Fig16. Dwelling plan of type C3 (OPTION 1)

Fig17. Dwelling plan of type B (OPTION 2)