Building Energy Performance Report

Mellon Arena Project Multi-family Housing || Block C4 ENERGY PLUS REPORT 48-722 Building Performance & Modeling Carnegie Mellon University

RUSSELL harmon /russellh@andrew.cmu.edu/

Duy Vo /dvo@andrew.cmu.edu/

48-722 Building Performance & Modeling || Energy Plus Final Report

Table of Figures A. PROJECT OVERVIEW INTRODUCTION Objectives & methodology Building case study description

B. BASELINE MODEL Thermal zones LOCATION & WEATHER DATA OPERATING SCHEDULES building envelope GLAZING TYPE HVAC SYSTEM BASELINE ENERGY PERFORMANCE

C. PROPOSED DESIGN ALTERNATIVES DESIGN ALTERNATIVE 1 SPECTRAL GLAZING ENERGY PERFORMANCE DESIGN ALTERNATIVE 2 ALTERNATIVE HVAC + SPECTRAL GLAZNG ENERGY PERFORMANCE DESIGN ALTERNATIVE 3 PROPOSED ENVELOPE ENERGY PERFORMANCE

D. COMPARISONS & DISCUSSIONS Comparison a: BASELINE vs. alt 1 COMPARISON B: ALT 1 VS. ALT 2 COMPARISON C: BASELINE VS. ALT 3

E. EPILOGUE Conclusions PROJECT LIMITATIONS

F. REFERENCES

Table of Content 2 3 3 4 5

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5 6 7 13 14 15 16

16 16 16 17 18 18 19 21 20 22

23 23 24 26

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Table of FIGURES Figure 1. Block C4’s location in relation to Mellon Arena Redevelopment Figure 2. Comparison Procedure Diagram Figure 3. Block C4’s Surrounding Site and Its Axonometric Rendering Figure 4. ASHRAE Climate Zone Map Figure 5. Climate-Consultant-generated Chart on Monthly Diurnal Averages || Allegheny County, Pittsburgh Figure 6. Block C4: Unit Interior Layout Figure 7. Operating Schedule Template Break-down Figure 8. Baseline Lighting Properties Figure 9. Kitchen Operating Schedules (Weekdays) Figure 10. Bathroom Operating Schedules (Weekdays) Figure 11. Staircase Operating Schedules (Weekdays) Figure 12. Living Room Operating Schedules (Weekdays) Figure 13. Garage Operating Schedules (Weekdays) Figure 14. Bedroom Operating Schedules (Weekdays) Figure 15. Wall Assembly Figure 16. Unoccupied Pitched Roof Assembly Figure 17. On-grade Floor Slab Assembly Figure 18. Double Pane Glass Window (2) Figure 19. Baseline HVAC System Nodal Diagram Figure 20. Baseline Model Simulated Performance Data Figure 21. Design Alternative #1 Energy Performance Figure 22. Proposed HVAC system nodal diagram Figure 23. Design Alternative #2 Energy Performance Data Figure 24. Wall Assembly Figure 25. Unoccupied Pitched Roof Assembly Figure 26. On-grade Floor Slab Assembly Figure 27. Quadruple Pane Glass Window (3) Figure 28. Design Alternative #3 Energy Performance Data Figure 29. Energy Use: Baseline vs. Spectral Glazing Figure 30. Baseline vs. Alternative 1: Percentage Difference in Energy Consumption Figure 31. Alternative 1 vs. Alternative 2: Percentage Difference in Energy Consumption Figure 32. Energy Use: Alternative HVAC vs. Spectral Glazing Figure 33. Baseline vs. Alternative 3: Percentage Difference in Energy Consumption Figure 34. Energy Use: Baseline vs. Alternative Envelope Figure 35. Peak Loads: Baseline vs. Alternative Envelope Figure 36. Percentage Difference in EUI across all models Figure 37. EUI Comparison of All Models Figure 38. Annual Energy Consumption By Month

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A. PROJECT OVERVIEW INTRODUCTION The goal of this project is to investigate various parameters of building energy performance and to identify the most energy efficient design alternative for “Block C4” within the scope of the assigned course work. “Block C4” is a multi-family townhouse Building in Pittsburgh, Pennsylvania. Four energy models were created to explore the energy performance of the building using Design Builder 3 and the department of Energy’s Energy Plus 7 software. The first of the four models is a baseline model that was designed to comply with ASHRAE standards with standard building materials. The next three models are all modifications of this baseline model:

(Alt 1) This alternative changed the calculation algorithm method to spectral glazing from the simple glazing algorithm for windows. This single modification increased solar heat gain significantly in the summer, and thus increased the cooling load by 49.2%.

(Alt 2) This alternative kept the spectral glazing method and changed the baseline HVAC system to a Constant Volume Direct-Expansion (DX)” system using unitary multizone HVAC system. The result was that the time comfort set point not met was increased dramatically to a total of 32.6% of the year.

(Alt 3) The final alternative of this project explored the effect of the addition of a highly insulated building envelope with R83 walls, R9 windows, and an R32 roof/ground floor to the baseline model. This alternative had the most positive results, and decreased the energy use intensity of the baseline by 11.2%.

NORTH Master plan of mellon arena

CURRENT SITE OF mellon arena

Figure 1. Block C4’s location in relation to Mellon Arena Redevelopment

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OBJECTIVES & METHODOLOGY

This project explored the four energy models of “Block C4� using Design Builder and Energy Plus.

First, the geometry of the building and surrounding context was modeled base on the redevelopment plan of Mellon Arena in downtown Pittsburgh. We assigned the defined internal spaces in the townhouses practical functions for multifamily housing and used default design builder templates for multi-family occupant density.

The occupant activity schedules were also based on design builder templates for the specific uses we assigned to the rooms. For instance, the kitchen template was assigned to one of the rooms on the first floor which we defined to be the kitchen. The equipment and lighting schedules align with the occupancy schedules.

Compliance with ASHRAE standards guided the design of the building envelope from the ground floor, walls, windows, and the roof assemblies. These assemblies were constructed from standard low-rise multi-family building materials i.e. light wood framing with a brick exterior cladding. Also for each assembly, the simple calculation algorithm methods were used, which means most systems were defined by their U value. The following design alternatives as described in the introduction were predefined by the project parameters.

However, these alternatives explore several significant building energy consumption related topics: the effects of windows, HVAC systems, and building envelopes. Lastly, an analysis of all four models included the parameters of energy consumption, energy use intensity, seasonal energy consumption, peak design loads, and the time the comfort set point was not met. In sum, a baseline model was created and systems were modified systematically to explore the effects on the total building performance.

BASELINE

(SIMPLE glazing) + (baseline hvac) + (baseline envelope)

Peak Design Loads Seasonal Energy (Winter vs. Summer) Time Set Point Not Met Analysis Greatest ENERGY consumer

DESIGN ALT #1 (Spectral glazing) + (baseline hvac) + (baseline envelope)

ENERGY USE INTENSITY

DESIGN ALT #2 (Spectral glazing) + (Alternative hvac) + (baseline envelope)

Annual site-source energy analysis HEATING COOLING FANS & PUMPS LIGHTS SHW SYSTEM

DESIGN ALT #3 (SIMPLE GLAZING) + (baseline hvac) + (proposed envelope)

Figure 2. Comparison Procedure Diagram

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BUILDING CASE STUDY DESCRIPTION

Block C4 is a multifamily townhouse structure with five, 4 story units. Each unit has three floors positioned over a garage. The east and west facades of the units are shared walls, except for the end units. The south and north facades line up with adjacent units, creating an overall rectangular shape with its long axis oriented from east to west. The total floor area is 1,251m2, and the total conditioned area is 1021 m2. The south-west façade has a window to wall ratio of 26% (68m2 total), and the north-east façade has 22% (57m2 total) ratio of window compared to wall area. Each unit has a total of 7 rooms which each have 1 associated thermal zone each.

Figure 3. Block C4’s Surrounding Site and Its Axonometric Rendering

B. BASELINE MODEL THERMAL ZONEs

Figure 6. Block C4: Unit Interior Layout

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The garage and the space below the gable roof are the only semi-exterior unconditioned zone in the whole entire unit. The garage, due to its negligible occupancy density at all points during the day, was considered to be unconditioned, meaning there is no need for heating or cooling. Similarly, the space under the gable roof , though contributing to the overall thermal performance of the building, is unoccupied; thus it is unconditioned.

The remainder zones are set to be standard, which means that they are occupied and require heating and cooling seasonally. In terms of adjacency, “Auto” mode was selected for all 55 thermal zones, meaning that Design Builder automatically assigns the adjacency of each surface of a thermal zone based on its position inside the model.

LOCATION & WEATHER DATA

Pittsburgh lies within a temperate zone at about 40 ° N latitude, and 80° W longitude. Temperatures reach below freezing in the winter and up about 30 °C in the summer. The relative humidity is almost always high, most commonly being within 80-90% especially during the summer months. There are uncommonly completely clear skies, mostly the cloud cover is a varying amount of partial cover, and 43% of the total time the sky is completely overcast. The ground level wind speeds are generally mild, probably due to the hilly terrain. According to ASHRAE standard 90.1, Pittsburgh falls within the climate zone 5 (Marine). It has an average annual rainfall of 37.85 inches. In other words it is a temperate, fully humid, and warm summer climate with a cold winter. This means that we should expect both heating loads in the winter and cooling load in the summer, with natural ventilation limited by humidity.

Climate Data Heating Design Temperature

-15.4oC

Standard Heating Degree Days

1293 32.2oC

Cooling Design Temperature Standard Cooling Degree Days Maximum Dry Bulb Temperature Minimum Dry Bulb Temperature

486 32.7oC -16.7oC

ASHRAE Climate Zone Figure 4. ASHRAE Climate Zone Map (1)

5A

Heating dominant climate

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Figure 5. Climate-Consultant-generated Chart on Monthly Diurnal Averages || Allegheny County, Pittsburgh Figure 5, previously retrieved from Climate Consultant software, indicates that Allegheny County, Pittsburgh experiences more “cold” days (comfort zone highlighted in grey) than “hot” days. Moreover, the standard Heating Design Day (HDD) for this particular climate zone is almost 3 times more than the standard Cooling Design Day (CDD). Thus, it is safe to say that Pittsburgh, especially Allegheny County, is a heating dominant temperate climate.

OPERATING SCHEDULES Activity Template Occupancy Density (people/m2) Metabolic Rate Cooling Set point temperature Cooling Setback Heating Set point temperature Heating Setback

Kitchen

Bedroom

Bathroom Living Room

Staircase

Garage

DB Domestic Kitchen

DB Domestic Bedroom

DB Domestic Bathroom

DB Domestic Living Room

DB Domestic Circulation

DB Common Circulation Area

0.0237

0.0188

0.0155

0.0187

0.0196

0.0229

0.9

0.9

0.9

0.9

0.9

0.9

25oC

25oC

25oC

25oC

25oC

25oC

28oC

28oC

28oC

28oC

28oC

28oC

21oC

21oC

18oC

18oC

18oC

18oC

12oC

12oC

12oC

12oC

12oC

12oC

Figure 7. Operating Schedule Template Break-down All four types of schedules align and are based on the assumed function of each zone and are used in each of the four building models. The four types of schedules in order of hierarchy are: Occupant activity, fans (HVAC), lighting, and equipment. This means that the occupancy schedule determines the operation times of

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the other three schedules. For example, if a room were unoccupied for a time, the lights, equipment, and HVAC system would be ready but not active. All schedules, except for Garage Occupancy schedule, were selected from provided templates available inside Design Builder under the category of “Residential Spaces”.The garage schedule was made by us based on our personal assumptions for the closest-to-realistic garage’s occupancy pattern.

Zones, though with different names, sizes, and location, that have similar function are set to have the same operating schedules. For instance, the “fun room” and the” living room”, though have different names, different sizes and different locations, are similar in function,; thus share the same operating schedules.

LIGHTING ASPECT

Lighting properties

Lighting energy Target Zone Illuminance

6.45 W/m2 100 lux

ASHRAE 90.1.2010 Compliance Lighting Control Type of Control Luminaire Type Radiant Fraction (7) Visible Fraction (7) Convected Fraction (7) Maximum Glare Index

(4)

On Stepped (Number of steps = 3) Surface Mounted 0.72 0.18 0.1 22

Figure 8. Baseline Lighting Properties

KITCHEN (EPD + LPD + O.d)

Figure 9. Kitchen Operating Schedules (Weekdays)

WEEKDAYS

EQUIPMENT

OCCUPANCY

LIGHTING

00:00 - 24:00

0.066

0

0

HOLIDAYS

Equipment

Occupancy

Lighting

00:00 - 24:00

0.066

0

0

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BATHROOM (EPD + LPD + O.d)

Figure 10. Bathroom Operating Schedules (Weekdays)

WEEKDAYS

EQUIPMENT

OCCUPANCY

LIGHTING

00:00 - 24:00

0.059

0

0

HOLIDAYS

Equipment

Occupancy

Lighting

00:00 - 24:00

0.059

0

0

STAIRCASE (EPD + LPD + O.D)

Figure 11. Staircase Operating Schedules (Weekdays)

Weekends

Equipment

Occupancy

Lighting

00:00 - 7:00 7:00 - 23:00 23:00 - 24:00

0.064 1 0.344

0 1 0.3

0 1 1

Holidays

Equipment

Occupancy

Lighting

00:00 - 7:00 7:00 - 23:00 23:00 - 24:00

0.064 1 0.344

0 1 0.3

0 1 1

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LIVING ROOM (EPD + LPD + O.d)

Figure 12. Living Room Operating Schedules (Weekdays)

Weekends

Equipment

Occupancy

Lighting

00:00 - 7:00 7:00 - 16:00 16:00 - 18:00 18:00 - 22:00 22:00 - 23:00 23:00 - 24:00

0.064 1 1 1 1 0.344

0 0 0.5 1 0.667 0

0 0 1 1 1 0

Holidays

Equipment

Occupancy

Lighting

00:00 - 7:00 7:00 - 16:00 16:00 - 18:00 18:00 - 22:00 22:00 - 23:00 23:00 - 24:00

0.064 1 1 1 1 0.344

0 0 0.5 1 0.667 0

0 0 1 1 1 0

GARAGE (EPD + LPD + O.d)

Figure 13. Garage Operating Schedules (Weekdays)

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Weekends

Equipment

Occupancy

Lighting

00:00 - 9:00 9:00 - 11:00 11:00 - 13:00 13:00 - 21:00 21:00 - 24:00

0 0 0 0 0

0 0 1 0 0

0 1 1 1 0

HOLIDAYS

Equipment

Occupancy

Lighting

00:00 - 9:00 9:00 - 21:00 21:00 - 24:00

0.064 1 0.344

0 1 0.3

0 1 0

BEDROOM (EPD + LPD + O.D)

Figure 14. Bedroom Operating Schedules (Weekdays)

Weekends

Equipment

Occupancy

Lighting

00:00 - 7:00 7:00 - 8:00 8:00 - 9:00 9:00 10:00 10:00 - 17:00

0 0.535 1 0.535 0.069

1 0.5 0.25 0 0

0 1 1 1 0

17:00 - 18:00 18:00 - 19:00 19:00 - 22:00 22:00 - 23:00 23:00 - 24:00

0.302 0.535 0 0 0

0 0 0 0.25 0.75

0 0 0 0.2 0

Holidays

Equipment

Occupancy

Lighting

00:00 - 7:00 7:00 - 8:00 8:00 - 9:00 9:00 - 22:00 22:00 - 23:00

0 0 0 0 0

1 0.5 0.25 0 0.25

0 0 0 0 0

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Inaccuracies in the Design Builder have been detected through the process of applying them to the building thermal zones. For instance, on weekends and holidays the Design Builder templates assume 0 occupancy, which causes the schedules for the lighting, equipment, and HVAC system to be turned off completely. In addition, lighting schedules seem to have been created with the occupant’s worst usage pattern in mind, as they only reflect whether the lights are fully off or fully on. There is no in-between setting, which we believe makes the schedules somewhat unrealistic.

Moreover, lighting does not correlate very well with occupancy. For instance, figure 9 indicates that during the period between 19:00 and 23:00, occupancy schedule in the bedroom does not reach its full FTE ratio (1), while the lighting schedule, on the contrary, reaches its maximum FTE ratio. Realistically speaking, when an occupant is in a bedroom during that period, he or she may only need to use a table lamp, which makes up a small FTE ratio, instead of all lighting systems present in the room

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Building Envelope The envelope plays an important role in the overall energy performance of the building., as it is exposed and directly affected by the climate in which the building is located. For the baseline of this project, we decided to compose an ASHRAE 90.1.2010 compliant building enclosure system, which is comprised of wall, slab on-grade floor, unoccupied pitched roof and window. The assemblies selected below are provided by Design Builder v3 as its default options. The window, in this case, was created using the “Simple” method, meaning pre-determined specifications (ASHRAE compliant) such as Solar Heat Gain Coefficient (SHGC), Light Transmission (LT) and Heat Transfer Value (U-value) were manually input into Design Builder v3.

WALL ASSEMBLY ASSEMBLY SPECIFICATIONS 0.1 m

Brickwork Outer leaf XPS Extruded Polystyrene

0.082 m

Pine (20% Moist)

0.1 m

Gypsum Plastering

0.013

U Value (W/m2-K)

0.291

U Value (Btu/hr sq.ft K)

0.051 20

R Value Figure 15. Baseline Wall Assembly

ASHRAE 90.1.2010 COMPLIANCE

(4)

UNOCCUPIED PITCHED ROOF ASSEMBLY ASSEMBLY SPECIFICATIONS Clay tile (roofing) Air Gap

0.025 m 0.02 m

Roofing Felt

0.005 m

MW Glass Wool (rolls)

0.133 m

U Value (W/m2-K)

0.273

U Value (Btu/hr sq.ft K)

0.048

R Value Figure 16. Unoccupied Pitched Roof Assembly

ASHRAE 90.1 2010 COMPLIANCE

21 (4)

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ON-GRADE FLOOR SLAB ASSEMBLY SPECIFICATIONS Timber Flooring Floor/Roof Screed

0.025 m 0.07 m

Cast Concrete Urea Formaldehyde Foam

0.1 m 0.185 m

U Value (W/m2-K)

0.188

U Value (Btu/hr sq.ft K)

0.033 30

R Value Figure 16. On-grade Floor Slab Assembly

ASHRAE 90.1.2010 COMPLIANCE

(4)

WINDOW SELECTION ASSEMBLY SPECIFICATIONS Definition Method

Simple 23%

Window to wall % SHGC Light Transmission

0.4 0.781

U-Value (W/M2-K)

1.99

U Value (Btu/hr sq.ft K)

0.35 3

R Value Figure 17. Double Pane Glass Window (2)

ASHRAE 90.1.2010 COMPLIANCE

(4)

GLAZING TYPE For the baseline model, “Simple Glazing” definition was selected to assist with the choosing of windows with certain expected specifications. This definition requires users to input U-value, SHGC and Visible Transmittance (VT) data in order to define the glazing properties for the overall glazing system. For the baseline, these 3 pieces of data were provided based ont the minimum window R-value requirements from ASHRAE standard. In addition, it is important to note that “Simple Glazing” definition does not take into account the heat transfer coefficient of the window frame, therefore a slight inaccuracy in the overall U-value of the window system is expected.

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HVAC Systems For the baseline model, the “Split and Separate Mechanical Ventilation” HVAC system was selected, as it is a commonly used system for most residential buildings. However, for this particular system, Design Builder assumes that every zone has its own”complete” heating and cooling system. We speculated that this assumption may be based on the use of traditional standalone HVAC window unit. Regardless, this assumption deems to be unrealistic, as it is not possible for each individual zone within the building to have their own boiler unit.

nodal chart of baseline Hvac system (Split and seperate mechanical ventilation) Repeated for all 50 zones 5-1STFLOOR: 1ST KITCHEN AHU HEATING COIL

5-1STFLOOR: 1ST KITCHEN AHU COOLING COIL

5-1STFLOOR: 1ST KITCHEN AHU SUPPLY FAN Air loop outlet node

Mixed air outlet node

cooling coil air inlet node

zone equipment inlet node

HEATing coil air inlet node

cooling coil water inlet node

5-1STFLOOR:1 ST KITCHEN AHU ZONE SPLITTER

HEATing coil water inlet node cooling coil water outlet node

Relief air outlet node Primary

HEATing coil water OUTlet node 5-1STFLOOR:1 ST KITCHEN DAMPER INLET NODE

Primary

5-1STFLOOR:1 ST KITCHEN DAMPER

5-1STFLOOr : 1ST KITCHEN AHU OA MIXING BOX

ZOne

5-1STFLOOR:1 ST KITCHEN DAMPER OUTLET NODE

5-1STFLOOR: 1ST KITCHEN

5-1STFLOOR: 1ST KITCHEN Outlet node Outdoor Air Inlet Node Air loop inlet node 5-1STFLOOR: 1ST KITCHEN AHU ZONE MIXER

Return air mixer outlet node

Figure 19. Baseline HVAC System Nodal Diagram

BASELINE ENERGY PERFORMANCE Though the energy use intensity for the baseline model is a respectable 37.2% less than the national average for multi-family housing there is room for improvement. Despite meeting all requirements from ASHRAE Standards, the energy performance of the building could be improved in many ways, including:

1. Lighting system: Modification of the baseline lighting was not included as one of the parameters of this particular project. However, due to the considerable energy consumption of this system, further studies should explore daylighting as well as energy efficient lighting systems in order to reduce the energy consumption of this system.

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2. Heating: Heating consumes 506% more energy than cooling in the baseline model. There are two strategies that we have identified to reduce the energy consumption from heating:

a. Improve thermal performance of the envelope. This option is further studied in alternative 3.

b. Increase solar heat gain with thermal mass in winter and shade windows from direct solar

gains during the summer. An exploration of these strategies is not included in this project.

Since air-flow is required for heating and cooling, an improvement on performance for heating will in turn reduce the amount of energy used for fans and pumps in the HVAC system. Additionally, reduction in heating loads will likely reduce peak heating loads, which ultimately helps reducing the size of the HVAC system.

EUI (kWh/m2/year) Peak Calculated Loads (kW) Energy Use (kWh) (Normalized kWh/m2)

83.50 Heating Cooling Fans and Pumps Lights Service Hot Water Heating Cooling Total

Time Comforto Set Point Not Met (hours)

84.87 30.68 14,726 (14.42) 17,814 (17.44) 5,523 (5.41) 31,596 (30.95) 6,236 (6.11) 85,247 (83.50) 0 (5,710.17 ASHRAE 55-2004)

(Tolerance ± 0.2 C)

Seasonal Energy Use (kWh)

Winter

36,324 (35.58)

(normalized kWh/m2)

Summer

16,508 (16.17)

Greatest Energy Consuming System (kWh) Comparison to National Average (133 kWh/m2/year) (6)

Heating @ 31,596 37.2% less

Figure 20. Baseline Model Simulated Performance Data (*) Winter months: December, January, and February Summer months: June, July, and August

c. PROPOSED DESIGN ALTERNATIVES DESIGN ALTERNATIVE 1 SPECTRAL GLAZING

This alternative is the same as the baseline model except that a “Spectral glazing” algorithm is used to calculate the effect of the windows on energy performance rather than the baseline “simple glazing” algorithm.

In the spectral glazing algorithm, the window stays the same and only the inputs of the material change. Now, the material definitions of the window assembly materials include: the Solar Heat Gain Coefficient (SHGC), Heat Transfer coefficient (U-value) and Light Transmittance. This one change has a dramatic effect on the thermal performance on the model as seen in fig. 21.

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ENERGY PERFORMANCE EUI (kWh/m2/year) Peak Calculated Loads (kW) Energy Use (kWh) (Normalized kWh/m2)

89.37 Heating Cooling Fans and Pumps Lights Service Hot Water Heating Cooling Total

Time Comforto Set Point Not Met (hours)

0 (5,381.67 ASHRAE 55-2004)

(Tolerance Âą 0.2 C)

Seasonal Energy Use (kWh) (normalized kWh/m2)

Winter Summer

Greatest Energy Consuming System (kWh) Comparison to National Average (133 kWh/m2/year) (6)

87.83 45.79 18,848 (18.46) 17,770 (17.40) 5,523 (5.41) 29,359 (28.76) 10,396 (10.18) 91,250 (89.37)

36,915 (36.16) 20,546 (20.12) heating at 29,359 32.8% less

Figure 21. Design Alternative #1 Energy Performance (*) Winter months: December, January, and February Summer months: June, July, and August

ANALYSIS In this design alternative, only the algorithm method for the windows was changed. With more parameters for the same material, Energy Plus conducts a more detailed analysis of the effect of solar heat gain etc. The result is that cooling loads increase because the windows are not shaded against direct sun light in the summer and Energy Plus now takes that into account. Since this is the only design change, it accounts for the entirety of the 49.2% increase in cooling peak load and the 24.4% increase in cooling and fan energy consumption versus the baseline. During the winter the models are quite similar, but the increased solar heat gains are still evident on fig. 38.

DESIGN ALTERNATIVE 2 HVAC System

A Constant Volume Direct-Expansion (DX) system using unitary multizone was selected as the alternative HVAC system for this project. This is a typical system with heating and cooling coils in a central air handling unit that splits the conditioned air to each zone. It is similar to the baseline split and separate mechanical ventilation system, except that there is a central air handling unit and only one control zone. This means that every zone is conditioned to the needs of the control zone. This is a strong contrast to the baseline HVAC system which had a control system for every conditioned zone. We selected the living room as the thermostatic control zone, since its temperature is representative of the temperature for the whole building.

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nodal chart of Alternative Hvac system (Constant volume dx using unitary multizone) AHU HEATING COIL

AHU COOLING COIL

AHU SUPPLY FAN Air loop outlet node

cooling coil water inlet node

AHU ZONE SPLITTER

HEATing coil water inlet node cooling coil water outlet node

Relief air outlet node

HEATing coil water OUTlet node zone INLET NODE Primary

all zones

zone Outlet node

SPLIT for all 50 zones

Primary

AHU OA MIXING BOX

zone equipment inlet node

HEATing coil air inlet node

ZOne

Mixed air outlet node

cooling coil air inlet node

Outdoor Air Inlet Node Air loop inlet node AHU ZONE MIXER

Return air mixer outlet node

Figure 22. Proposed HVAC system nodal diagram

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ENERGY PERFORMANCE EUI (kWh/m2/year) Peak Calculated Loads (kW) Energy Use (kWh) (Normalized kWh/m2)

77.33 Heating Cooling Fans and Pumps Lights Service Hot Water Heating Cooling Total

Time Comforto Set Point Not Met (hours)

2,856.5 (5,400.17 ASHRAE 55-2004)

(Tolerance Âą 0.2 C)

Seasonal Energy Use (kWh) (normalized kWh/m2)

Winter Summer

Greatest Energy Consuming System (kWh) Comparison to National Average (133 kWh/m2/year) (6)

87.83 45.79 28,217 (27.64) 17,770 (17.40) 5,523 (5.41) 40,056 (39.23) 18,089 (17.72) 78,953 (77.33)

15,450 28,403 heating at 40,056 41.9% less

Figure 23. Design Alternative #2 Energy Performance Data (*) Winter months: December, January, and February Summer months: June, July, and August

ANALYSIS

The alternative HVAC system saves energy compared to the baseline, with or without the inclusion of spectral glazing. However, this is not because it is more efficient, it is because it cannot keep the temperature within the required comfort zone for 32.6% of the year, especially in summer months. The time set point not met is considerable: 1,429.7 heating hours and 1,427.33 cooling hours. The higher figure for cooling can be ascribed to the increased solar heat gains from using the spectral glazing algorithm. The alternative HVAC system simply cannot keep up with the heating and cooling loads, or because of the control system is not told to do so. For example, the control zone may be comfortable, but it could be too cold in the upstairs rooms and the system would not tell the HVAC system to change this. In total, there is a 7.4% energy savings compared to the baseline and 13.4% better than the spectral glazing model, but it is not worth it because the occupants will be uncomfortable more than 300 hours out or the year.

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DESIGN ALTERNATIVE 3 Building Envelope As described in the baseline model analysis, the addition of a highly insulated building envelope can significantly reduce the energy consumption of the building. The temperate climate of Pittsburgh is also conducive to this design alternative with associated benefits projected for the whole year. All exterior assemblies from the ground floor, roof, walls, and windows, were redesigned to be more insulating with increased air tightness through a structurally insulated panel system that was utilized effectively in a previous study.

WALL ASSEMBLY

ASSEMBLY SPECIFICATIONS Brickwork, Outer Leaf Oriented Strand Board (OSB) EPS Expanded Polystyrene

0.044 m 0.01 m 0.499 m

Oriented Strand Board (OSB)

0.01 m

Plaster (Lightweight)

0.01 m

U Value (W/m2-K)

0.068

U Value (Btu/hr sq.ft K)

0.012 83

R Value Figure 24. Wall Assembly

EXCEED ASHRAE 90.1.2010

(4)

UNOCCUPIED PITCHED ROOF ASSEMBLY ASSEMBLY SPECIFICATIONS Wood Shingles

0.01 m

Oriented Strand Board (OSB)

0.01 m

EPS Expanded Polystyrene

0.177 m

Oriented Strand Board (OSB)

0.133 m

U Value (W/m2-K)

0.178

U Value (Btu/hr sq.ft K)

0.031

R Value Figure 25. Unoccupied Pitched Roof Assembly

EXCEED ASHRAE 90.1 2010

32 (4)

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ON-GRADE FLOOR SLAB ASSEMBLY SPECIFICATIONS Timber Flooring Floor/Roof Screed

0.025 m 0.07 m

Cast Concrete Urea Formaldehyde Foam

0.1 m 0.239 m

U Value (W/m2-K)

0.15

U Value (Btu/hr sq.ft K)

0.026 38

R Value Figure 26. On-grade Floor Slab Assembly

EXCEED ASHRAE 90.1.2010

(4)

WINDOW ASSEMBLY SPECIFICATIONS Definition Method

Simple

Window to wall %

22%

SHGC

0.45

Light Transmission

0.62

U-Value (W/M2-K)

0.66

U Value (Btu/hr sq.ft K)

0.116 9

R Value Figure 27. Quadruple Pane

Glass Window (3)

EXCEED ASHRAE 90.1.2010

(4)

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ENERGY PERFORMANCE EUI (kWh/m2/year) Peak Calculated Loads (kW) Energy Use (kWh) (Normalized kWh/m2)

74.17 Heating Cooling Fans and Pumps Lights Service Hot Water Heating Cooling Total

Time Comforto Set Point Not Met (hours)

0 (5,205 ASHRAE 55-2004)

(Tolerance Âą 0.2 C)

Seasonal Energy Use (kWh) (normalized kWh/m2)

Winter Summer

Greatest Energy Consuming System (kWh) Comparison to National Average (133 kWh/m2/year) (6)

79.57 30.93 14,317 (14.02) 17,983 (17.61) 5,523 (5.41) 20,058 (19.65) 8,498 (8.32) 75,731 (74.17)

28,705 17,994 Heating at 20,058 44.2% less

Figure 28. Design Alternative #3 Energy Performance Data (*) Winter months: December, January, and February Summer months: June, July, and August

ANALYSIS This option explored the recommendation to improve the baseline model envelope by increasing the amount of insulation. The results are significant, with an 11.2% reduction in the energy use intensity of the building. The reduction of energy consumption is significant in the winter months at 21% compared to the summer season increase of 9%. However, the peak loads were reduced less significantly than the total energy consumption with only a 6.2% peak heating load reduction and 0.8% increase in the peak cooling load. In sum, the improved envelope has helped to reduce and balance the peak loads and energy consumption of the building and it now operates with 44.2% less energy use intensity than the national average.

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D. COMPARISONS & DISCUSSIONS comparison a: BASELINE vs. alt 1 Design Alternative 1 = Baseline Envelope + Baseline HVAC + Spectral Glazing

Figure 29. Energy Use: Baseline vs. Spectral Glazing (*) Winter months: December, January, and February Summer months: June, July, and August

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Compared Category

Percentage difference from baseline model

Total Energy Use Annual Fans & Pumps Energy Use Annual Lighting Energy Use Annual Heating Energy Use Annual Cooling Energy Use Winter Energy Use Summer Energy Use

7% increase 27.9% increase 0.2% decrease 7.6% decrease 40% increase 1.6% increase 24.5% increase

Figure 30. Baseline vs. Alternative 1: Percentage Difference The results from Energy Plus indicated that alternative design 1, with spectral glazing as the only change, requires 40% more energy for cooling than that of the baseline. This particular spike in cooling energy use for the building is derived from the different input algorithm used in design alternative 1. Unlike the “Simplified Glazing” method used in the baseline model, “Spectral Glazing” requires specific information of the window’s material layers instead of its expected performance properties such as Solar Heat Gain Coefficient (SHGC), Light Transmittance (LT) or Solar Heat Transfer coefficient (U-value). We speculated that the “spectral glazing” window, as analyzed by Energy Plus, had a high SHGC value, meaning that it more likely to transmit solar heat inside. This coupled with the lack of shading devices, though advantageous during the winter months as heating energy use decreases by 7.6%, causes the building to have significantly large amount of energy consumed for cooling during the summer months. Additionally, such big increase in cooling energy had a domino effect on annual fans & pumps energy use, summer energy use and total energy use, as all of them had increased.

comparison B: ALT 1 VS. ALT 2 Design Alternative 1 = Baseline Envelope + Baseline HVAC + Spectral Glazing Design Alternative 2 = Baseline Envelope + ALTERNATIVE HVAC + Spectral Glazing Compared Category

Percentage difference from DESIGN ALTERNATIVE 1

Total Energy Use Annual Fans & Pumps Energy Use Annual Heating Energy Use Annual Cooling Energy Use Winter Energy Use Summer Energy Use

15.6% increase 33.2% decrease 26.7% decrease 42.5% decrease 139% increase 27.6% decrease

Figure 31. Baseline vs. Alternative 2: Percentage Difference The alternative HVAC, specifically “Constant Volume DX”, is responsible for reduction in annual energy use for fans and pumps (33.2%), heating (26.7%), and cooling (42.5%) compared to that of the design alternative.

However, these merits are not due to the system having superior efficiency, it is because it has 2,856.5 hours comfort set point not met. This means that the “Constant Volume DX” system fails to maintain the temperature within the required comfort for 33.6% of the year, especially during the winter. This is reflected in an incredibly high increase of 139% in winter energy use compared to design alternative 1.

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Figure 32. Energy Use: Alternative HVAC vs. Spectral Glazing (*) Winter months: December, January, and February Summer months: June, July, and August

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comparison c: BASELINE vs. ALT 3 Design Alternative 3 = ALTERNATIVE Envelope + Baseline HVAC + SIMPLE Glazing)

Figure 33. Energy Use: Baseline vs. Alternative Envelope (*) Winter months: December, January, and February Summer months: June, July, and August

Compared Category

Percentage difference from baseline model

Total Energy Use Winter Energy Use Summer Energy Use Peak Heating Load Peak Cooling Load

11.2% decrease 26.5% decrease 9% increase 6.7% decrease 0.8% increase

Figure 34. Baseline vs. Alternative 3: Percentage Difference

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Design Alternative 3 explored the recommendation to improve the baseline model envelope in terms of thermal performance by increasing the amount of insulation. With various building enclosure systems such as walls, roof, floor slab and window becoming tighter, heat loss and gain are minimized. This notion is reflected in the significant results obtained from Energy Plus simulation, with 11.2% decrease in total energy use compared to the baseline.The reduction of 26.5% in energy use in winter months is comparatively more significant than the increase of 9% in energy use in summer months. Additionally, it is important to note that this increase energy use in summer months could be further minimized and even avoided, had shading devices been employed on the facades of the buildings.The peak cooling load is minimally affected, as it only increased by 0.8% compared to that of the baseline. On the contrary, the peak heating load is reduced by 6.7%. Overall, the envelope ungrade is effective, as it improves the overall building energy performance.

Figure 35. Peak Loads: Baseline vs. Alternative Envelope

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E. EPILOGUE CONCLUSIONS All models are below the national average multi-family house energy use intensity of 133kWh/m2 (6). The envelope design alternative balanced the annual heat loss and gains for a significant energy consumption reduction of 11.2% from the baseline of 83.5 kWh/m2. The use of the spectral glazing calculation algorithm is recommended because one should prepare for the worst case scenario. The alternative HVAC system is not recommended because it cannot meet the comfort requirements, but that does not mean exploring other HVAC systems in future studies will not lead to positive results. Also, in all models the lighting system is the second most energy intensive system. If the building owners were to invest in only one energy saving system beyond the highly-insulated envelope or highly efficient heating system, they would get the most potential benefit from reducing the energy consumption of their lighting system whether by changing their behavior patterns, increasing daylight in the interior spaces, or installing more efficient lighting systems.

SITE EUI (KWH) Spectral Glazing Alternative HVAC Alternative Envelope

Percentage difference from Percentage Difference baseline model from national AVERAGE 7% worse 7.4% better 11.2% better

32.8% better 41.9% better 44.2% better

Figure 36. Percentage Difference in EUI across all models

Figure 37. EUI Comparison of All Models

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Figure 38. Annual Energy Consumption By Month

PROJECT LIMITATIONS Upon the completion of this project, we have identified several limitations that may compromise the accuracy of the building’s overall energy performance. These limitations are derived from the assumptions made by Design Builder v3 as well as the disconnect between Energy Plus v7 and Design Builder v3.They are as follow: • As previously mentioned in section B under “Operating Schedules” category, we used activity templates provided by Design Builder v3 for this project. As we have discovered, the lighting schedule and occupancy schedule assumed for these templates do not correlate very well with each other. This ultimately creates unrealistic lighting use pattern, and occupancy pattern.

• In regards to window-to-wall percentage, in order to meet the requirement from ASHRAE 90.1.2010 Standard, we adjusted our percentage in using the window-to-wall ratio meter bar from Design Builder.

However, Energy Plus did not recognize the adjustment made in Design Builder as it only indicated the initial percentage that came from the provided Sketchup file. In order to properly address this problem, we then had to manually created more windows on both the North-East and South-West facades in order to have our percentage fall within the required range.

• The “Split and Separate Mechanical Ventilation” HVAC system in our baseline model is a default system provided by Design Builder v3. However, as previously stated in Section B, this system is derived based on an unrealistic assumption of each thermal zone in the building would have their own HVAC system with their own heating and cooling coils.

• Lastly, we’ve discovered some discrepancies with the wall assemblies, especially the stud wall system, as Design Builder had provided much more simplified layer composition for the assemblies than what we would have in reality.

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REFERENCES (1). Energy Modeling of Buildings - Available online: energymodeling.pbworks.com (2). Double Pane Glass Window - Available online: familyhandyman.com (3). Quadruple Pane Glass Window (Krypton filled) - Available online: familyhandyman.com (4). ASHRAE Standard 90.1.2010 Standard for Buildings Except Low-Rise Residential (5). ASHRAE Standard 55.2004 (6). US Energy Information Administration, 2005. “2005 Residential Energy Consumption Survey--Detailed Tables.�

- Available Online: http://www.eia.gov/emeu/recs/recs2005/hc2005_tables/detailed_tables2005.html (7). Lighting Handbook: Reference & Application, 8th Edition, Illuminating Engineering Society of North America, New York, 1993, p. 355

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