Energy modelling of a three-story primary school building located in Phoenix, Arizona

Energy modelling of a three-story primary school
building located in Phoenix, Arizona
MME 9646: Energy Modelling of Buildings
15th
April, 2016
Name: Kirtan Gohel Instructor Name: Dr. Kamran Siddiqui

1 | P a g e
SUMMARY:
Energy modelling of a three-story building located in Phoenix, Arizona has been carried out using
HAP software. Heating and cooling loads were calculated for both summer and winter conditions.
Weather conditions were referred from ASHRAE standards. HAP simulation was carried out for
given three different scenarios. Scenario 1 was the base case. VAV rooftop system was used for
the load calculation in scenario 1. In scenario 2, two different HVAC systems were considered for
energy modelling namely VVT system and VRF system. From energy consumption as well as
economic point of view, VRF system is more efficient and economical for that particular school.
In scenario 3, one major change in layout of the floor was made by orienting the gym linearly on
an east-west axis and schedules of occupancy, lighting and fan/thermostat were changed for VAV
rooftop system. Because of this modification, significant energy was saved and from economic
perspective it has reduced annual cost of operating the system.
1. INTRODUCTION:
Energy modelling of a three-story primary school building located in Phoenix, Arizona had to be
carried out. Layout of that school was prepared using AutoCAD. After preparing the layout,
simulation was carried out using Hourly Analysis program 4.91. Ventilation and Energy standards
used are ASHRAE Std 62.1-2010 and ASHRAE Std 90.1-2010 respectively.
In scenario 1, energy modelling had to be carried out for the proposed building layout of the school.
VAV rooftop system is used for that.
In scenario 2, comparison between two different types of HVAC systems had to be done for
meeting the energy demand and conclude which case is feasible from energy consumption and
economical point of view.
In scenario 3, one major change in the floor layout and schedules had to be made to improve the
energy usage. For calculating the cost associated with the operation of system, electricity and fuel
rates have to be considered in USD.
This school building consists of total 19 spaces. These spaces are zoned into 15 zones. The basic
aim is to perform these 3 different scenarios and to do energy modelling.

2 | P a g e
2. THEORY:
Orienting the school building properly is the first effective step for effective building. By proper
orientation, we can maximize the solar access and boost the effectiveness of daylight strategies.
Phoenix is located in the southwestern United States. Weather is quiet hot and dry in Phoenix,
Arizona. Based on the geographic location of Phoenix, orientation of the buildings should be
linearly on an east-west axis.
For calculation of load and cost associated, Hourly Analysis Program is very helpful.
2.1 Hourly Analysis program:
HAP is a powerful package that offers two different tools in a single package. First one is its ability
to design HVAC systems for commercial buildings and the second one is the strong energy
analysis capability for comparing energy consumption and costs associated with its operation.
HAP’s 8760 hours energy analysis results are very helpful in green building design. HAP energy
analysis results are accepted by US Green Building Council for its Leadership in Energy and
Environmental Design (LEED) rating system.[1]
Following are the main features of HAP:
1. It calculates design cooling and heating loads for spaces, zones and coils in HVAC system.
2. It determines required cooling and heating loads for spaces, zones and coils in HVAC
system.
3. It has an ability to size cooling and heating coils
4. It can size air circulation fans, chillers and boilers.
5. It can simulate hour-by-hour operations of all heating and cooling systems in building.
6. It can simulate hour-by-hour operation of all plant equipment in the building.
7. It has capability to simulate hour-by-hour operation of non-HVAC systems including
lighting and appliances.
8. It can generate tabular and graphical reports of hourly, daily, months and annual data.
So, there are the capabilities and basic features of HAP software.[2]

3 | P a g e
3. PROBLEM DESCRIPTION:
Primary school is located in Phoenix, Arizona. Walls and roof structure are insulated sufficiently.
Figure 3.1: First Floor
Figure 3.1 shows the layout of first floor of primary school. It is seen that, the first floor has 7
spaces. This 7 spaces are zoned into 6 different zones.
Figure 3.2: Second Floor
N
N

4 | P a g e
Figure 3.2 represents the layout of second floor. Second floor has 6 spaces. These spaces are zoned
into 5 zones.
Figure 3.3: Third Floor
Figure 3.3 represents third floor layout. Third floor is divided into 6 spaces. These spaces are zoned
into 4 zones.
3.1 Scenario 1: To conduct energy modelling of a three story building.
Here, the system has a capacity of 400 students attending the school. VAV rooftop system has
been employed for the energy modelling. There are 19 spaces and 15 zones. Main components of
the system are economizer, precool coil, preheat coil, central cooling coil, supply fan, duct system
and return fan. Both preheat coil and precool coil are set to 53 °F. Air-cooled DX is used as a
cooling source in precool coil and central cooling coil. Heating for the preheat coil is obtained by
the combustion of natural gas. Both precool and preheat coils are placed to the downstream of
mixing point. Central cooling coil supply temperature is 55 °F. Fans are forward curved with
dampers with a configuration of draw-thru and efficiency of 50%. Cooling supply temperature of
air to the space is set to 55 °F. Precool unit, Preheat unit and central cooling unit are auto sized.
Further, in central cooling unit oversizing factor is assumed 20%. Natural gas is the main source
for heating and air-cooled DX is the main source of cooling. Using HAP heating and cooling load
as well as operational cost has to be estimated.
3.2 Scenario 2: To compare two different HVAC system for this building:
Comparison was made between VVT and VRF system. For VVT system packaged vertical units
were used. Main components of this system are ventilation fan, economizer, precool coil, preheat
coil, central cooling coil, central heating coil, supply fan, duct system and return fan. Ventilation
N

5 | P a g e
system used is constant ventilation airflow type with 4 % damper leakage rate. Precool and preheat
coil are set to 53 °F. Central cooling coil is set to 55 °F and central heating coil is set to 95°F. In
both precooling coil and central cooling coil, cooling source is Air-cooled DX. On other hand, in
preheat and central heating coil, heating source is combustion of natural gas. Supply fan and return
fan both are forward curved with dampers.
In case of VRF system, terminal units of VRF system are used. Here, this system is common
ventilation type system. Main components of system are ventilation system, cooling coil, heating
coil, ventilation fan, duct system and exhaust fan. Ventilation system is constant ventilation airflow
type with 4 % damper leak rate. Cooling and heating coils are set to 75 °F and 70 °F respectively.
Cooling source for cooling coil is air-cooled DX and for heating coil electric resistance is the
heating source. In VRF system, there is no provision of using combustion of natural gas as a
heating source. So, electric resistance is the only heating source. Exhaust fans are forward curved
with dampers.
3.3: Major change is floor layout and schedules:
For particular this scenario, layout of the gym was changes. Initially, the gym was having north-
south orientation. But, for this scenario, its orientation was changed to east-west. Working hours
of the school was 8 a.m. to 3 p.m. But, for this scenario it was assumed that the school working
hours are 7 a.m. to 2 p.m. For this scenario, VAV system was used. So, comparison were made
between scenario 1 and scenario 3.
Figure 3.3.1: Modified layout of gym
Figure 3.3.1, represents the modified layout of gym along with the first floor layout.
Before and after schedules are represented here.
N

6 | P a g e
Before schedule After schedule
Fan/Thermostat Fan/Thermostat
Weekdays Weekends/Holidays Weekdays Weekends/Holidays
Hours 00-07: U Hours 00-23: U Hours 00-06: U Hours 00-23: U
Hours 08-15: O Hours 07-14: O
Hours 16-23: U Hours 15-23: U
Lighting Lighting
Hours 00-07: 10% Hours 00-07: 10% Hours 00-06: 10% Hours 00-06: 10%
Occupancy Occupancy
Hours 08-15: 100% Hours 07-14: 100%
Hours 16-23: 0% Hours 15-23: 0%
4. RESULTS AND DISCUSSION:
4.1 Results of scenario 1: VAV System
Energy modelling was done for this school using HAP software. In scenario 1, packaged rooftop
unit of VAV system is used.
From the system reports it has found that the total coil load associated with central cooling coil
and precool coil are 2.7 tons and 61.7 tons respectively.
So, the cooling load associated with precool coil is very high.
Table 4.1.1 represents the design cooling and heating loads associated with this VAV system.
From the results of this table it is clearly seen that the cooling load associated with this system is
very high compared to heating load. Zone conditioning is the main reason behind that lard cooling
load. On other hand, main contributor of heating load is load due to ventilation.
Latent cooling load on the system is negligible compared to sensible cooling load. Same thing
happens with sensible heating load. In case of heating load, latent heating load is negligible.
In table 4.4.1, for design cooling positive values are cooling loads and negative values are heating
loads. But, in design heating, positive values are heating loads and negative values are cooling
load.

7 | P a g e
DESIGN COOLING DESIGN HEATING
COOLING DATA AT Mar 1500 HEATING DATA AT DES HTG
COOLING OA DB / WB 94.0 °F / 61.8 °F HEATING OA DB / WB 34.0 °F / 28.5 °F
Sensible Latent Sensible Latent
ZONE LOADS Details (BTU/hr) (BTU/hr) Details (BTU/hr) (BTU/hr)
Window &
Skylight Solar
Loads
420 ft² 10830 - 420 ft² - -
Wall
Transmission
11415 ft² 7582 - 11415 ft² 13787 -
Roof
Transmission
9840 ft² 23972 - 9840 ft² 12696 -
Window
Transmission
420 ft² 2008 - 420 ft² 4884 -
Skylight
Transmission
0 ft² 0 - 0 ft² 0 -
Door Loads 40 ft² 922 - 40 ft² 459 -
Floor
Transmission
10560 ft² 0 - 10560 ft² 9801 -
Partitions 0 ft² 0 - 0 ft² 0 -
Ceiling 0 ft² 0 - 0 ft² 0 -
Overhead
Lighting
60383 W 159711 - 0 0 -
Task Lighting 6226 W 18590 - 0 0 -
Electric
Equipment
9700 W 29386 - 0 0 -
People 401 81577 110445 0 0 0
Infiltration - 0 0 - 0 0
Miscellaneous - 0 0 - 0 0
Safety Factor 0% / 0% 0 0 0% 0 0
>> Total Zone
Loads
- 334577 110445 - 41628 0
Zone
Conditioning
- 379127 110445 - 5024 0
Plenum Wall
Load
0% 0 - 0 0 -
Plenum Roof
Load
0% 0 - 0 0 -
Plenum Lighting
Load
0% 0 - 0 0 -
Return Fan Load 16875 CFM 67553 - 6528 CFM -31980 -
Ventilation Load 6528 CFM 91483 -110454 6528 CFM 187616 0
Supply Fan Load 16875 CFM 67553 - 6528 CFM -31980 -
Space Fan Coil
Fans
- 0 - - 0 -
Duct Heat Gain /
Loss
0% 0 - 0% 0 -
>> Total System
Loads
- 605717 -9 - 128680 0
Central Cooling
Coil
- 32536 0 - 0 0
Precool Coil - 572831 0 - 0 0
Preheat Coil - 0 - - 128680 -
>> Total
Conditioning
- 605368 0 - 128680 0
Key: Positive values are clg loads Positive values are htg loads
Negative values are htg loads Negative values are clg loads
Table 4.4.1: Design heating and cooling load with VAV system

8 | P a g e
Fig 4.1.1: Psychrometric analysis for VAV rooftop system
Figure 4.1.1 represents psychrometric analysis of VAV rooftop system. It can be seen that, process
1-2 represents that the fresh air enters and get mixed with return air at point 2. Then it is precooled
to point 3 and again it is cooled to point 4. Because of the supply fan its temperature increases upto
point 5. From point 5, air enters into the space. Point 6 represents room temperature. Point 7 is for
return fan outlet. Portion of that air mixes with fresh and again recirculates and rest of the air
exhaust from the system.
Table 4.1.2 and 4.1.3 represents air system simulation reports for VAV rooftop system. It can be
seen that from May to September there is no heating load on the preheat coil. On other hand, during
this time the load on the precool coil is comparatively high. It is clearly seen that there is significant
difference between the total yearly cooling and heating load associated with the system.
1. Outdoor Air
2. Mixed Air
3. Precool Coil Outlet
4. Central Cooling Coil Outlet
5. Supply Fan Outlet
6. Room Air
7. Return Fan Outlet
1
234 5
6 7
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.016
0.018
0.020
30 40 50 60 70 80 90 100
Location:Phoenix IAP, Arizona
Altitude:1106.0 ft.
Data for:March DESIGN COOLING DAY, 1500
SpecificHumidity(lb/lb)
Temperature ( °F )

9 | P a g e
Month
Precool Coil
Load
(kBTU)
Precool Eqpt
Load
(kBTU)
Precool Unit
Clg Input
(kWh)
Preheat Coil
Load
(kBTU)
Preheat Eqpt
Load
(kBTU)
Preheat Coil
Input
(kBTU)
Preheat
Heating Misc.
Electric
(kWh)
January 19344 19243 1455 2312 2312 2720 0
February 20708 20605 1570 2079 2079 2445 0
March 65323 65287 5265 545 545 641 0
April 94085 94062 8002 70 70 82 0
May 121498 121493 10971 0 0 0 0
June 159277 157890 16125 0 0 0 0
July 189880 183423 17943 0 0 0 0
August 180195 177108 16680 0 0 0 0
September 160319 159361 14628 0 0 0 0
October 102664 102645 8650 5 5 5 0
November 54511 54331 4357 498 498 586 0
December 19439 19310 1470 2279 2279 2681 0
Total 1187243 1174757 107120 7787 7787 9161 0
Table 4.1.2: Air system simulation report of VAV rooftop system
Month
Central
Cooling Coil
Load
(kBTU)
Central
Cooling Eqpt
Load
(kBTU)
Central Unit
Clg Input
(kWh)
Supply Fan
(kWh)
Return Fan
(kWh)
Lighting
(kWh)
Electric
Equipment
(kWh)
January 6329 3466 103 3738 3738 17265 1474
February 6198 3705 110 3669 3669 15986 1474
March 7807 7061 228 4654 4654 18118 1785
April 7967 7811 272 4779 4779 17478 1707
May 8434 8419 321 5065 5065 17691 1630
June 9125 9125 408 5470 5470 17478 1707
July 9466 9445 428 5649 5649 17904 1707
August 9242 9242 402 5536 5536 17904 1707
September 8722 8722 363 5218 5218 17478 1707
October 8184 8025 284 4709 4709 17691 1630
November 7559 6163 197 4109 4109 17052 1552
December 6161 3256 97 3601 3601 17052 1397
Total 95193 84439 3213 56197 56197 209098 19478
Table 4.1.3: Monthly air system simulation report

10 | P a g e
Fig 4.1.2: Annual component costs for VAV system
Component
Annual Cost
($) ($/ft²)
Percent of Total
(%)
Air System Fans 5,495 0.312 23.9
Cooling 5,456 0.309 23.7
Heating 893 0.051 3.9
Pumps 0 0.000 0.0
Heat Rejection Fans 0 0.000 0.0
HVAC Sub-Total 11,843 0.671 51.5
Lights 10,197 0.578 44.4
Electric Equipment 950 0.054 4.1
Misc. Electric 0 0.000 0.0
Misc. Fuel Use 0 0.000 0.0
Non-HVAC Sub-Total 11,147 0.632 48.5
Grand Total 22,990 1.303 100.0
Table 4.1.4: Annual component cost for VAV system
Figure 4.1.2 and table 4.1.4 represents annual component costs associated with that VAV rooftop
system. It can be seen that air system fans and cooling coil are mainly responsible for that total
cost. Cost associated with heating is very less compared to others. Out of total non-HVAC costs,
lights are mainly responsible for the non-HVAC cost.
23.9%Air System Fans
23.7%Cooling
3.9% Heating
44.4% Lights
4.1% Electric Equipment

11 | P a g e
Figure 4.1.3: Annual energy cost for VAV system
Component
Annual Cost
($/yr) ($/ft²)
Percent of Total
(%)
HVAC Components
Electric 10,950 0.621 47.6
Natural Gas 893 0.051 3.9
Fuel Oil 0 0.000 0.0
Propane 0 0.000 0.0
Remote Hot Water 0 0.000 0.0
Remote Steam 0 0.000 0.0
Remote Chilled Water 0 0.000 0.0
HVAC Sub-Total 11,843 0.671 51.5
Non-HVAC Components
Electric 11,147 0.632 48.5
Natural Gas 0 0.000 0.0
Fuel Oil 0 0.000 0.0
Propane 0 0.000 0.0
Remote Hot Water 0 0.000 0.0
Remote Steam 0 0.000 0.0
Non-HVAC Sub-Total 11,147 0.632 48.5
Grand Total 22,990 1.303 100.0
Table 4.1.5: Annual energy cost for VAV system
47.6%HVAC Electric
3.9% HVAC Natural Gas
48.5% Non-HVAC Electric

12 | P a g e
Figure 4.1.3 and table 4.1.5 represents annual energy costs associated with VAV system. It can be
seen that most cost associated with VAV system is due to electric cost.
Component
Site Energy
(kBTU)
Site Energy
(kBTU/ft²)
Source Energy
(kBTU)
Source Energy
(kBTU/ft²)
Air System Fans 383,486 21.740 1,369,593 77.641
Cooling 376,457 21.341 1,344,490 76.218
Heating 9,161 0.519 9,161 0.519
Pumps 0 0.000 0 0.000
Heat Rejection Fans 0 0.000 0 0.000
HVAC Sub-Total 769,104 43.600 2,723,244 154.379
Lights 713,442 40.445 2,548,009 144.445
Electric Equipment 66,457 3.767 237,348 13.455
Misc. Electric 0 0.000 0 0.000
Misc. Fuel Use 0 0.000 0 0.000
Non-HVAC Sub-Total 779,900 44.212 2,785,357 157.900
Grand Total 1,549,004 87.812 5,508,601 312.279
Table 4.1.6: Energy consumption by system component for VAV system
Table 4.1.6 represents annual energy consumption by system component. It can be seen that energy
consumed by air system fans and cooling coils is higher than that of heating for HVAC
components. Energy consumed by lights is highest compared to all other HVAC and Non-HVAC
components. It can be seen that energy consumption by Non-HVAC components is slightly higher
than that of HVAC components.
Table 4.1.7 shows annual energy consumption by energy source. Again, table shows that natural
gas consumption is very less compared to electricity. It is clearly seen that for non-HVAC
applications there is no natural gas consumption. For non-HVAC components, energy is only
consumed for electric application.

13 | P a g e
Component
Site Energy
(kBTU)
Site Energy
(kBTU/ft²)
Source Energy
(kBTU)
Source Energy
(kBTU/ft²)
HVAC Components
Electric 759,945 43.081 2,714,088 153.860
Natural Gas 9,161 0.519 9,161 0.519
Fuel Oil 0 0.000 0 0.000
Propane 0 0.000 0 0.000
Remote Hot Water 0 0.000 0 0.000
Remote Steam 0 0.000 0 0.000
Remote Chilled Water 0 0.000 0 0.000
HVAC Sub-Total 769,106 43.600 2,723,249 154.379
Non-HVAC
Components
Electric 779,895 44.212 2,785,339 157.899
Natural Gas 0 0.000 0 0.000
Fuel Oil 0 0.000 0 0.000
Propane 0 0.000 0 0.000
Remote Hot Water 0 0.000 0 0.000
Remote Steam 0 0.000 0 0.000
Non-HVAC Sub-Total 779,895 44.212 2,785,339 157.899
Grand Total 1,549,000 87.812 5,508,587 312.278
Table 4.1.7: Energy consumption by energy source for VAV system

14 | P a g e
Figure 4.1.4: Monthly component costs for VAV system
Month
Air System Fans
($)
Cooling
($)
Heating
($)
Pumps
($)
Heat Rejection
Fans
($)
HVAC Total
($)
January 358 75 157 0 0 590
February 356 81 152 0 0 589
March 426 251 113 0 0 790
April 432 374 102 0 0 908
May 519 579 0 0 0 1,098
June 547 827 0 0 0 1,374
July 560 910 0 0 0 1,470
August 551 851 0 0 0 1,402
September 526 755 0 0 0 1,281
October 490 465 100 0 0 1,055
November 383 212 112 0 0 707
December 347 75 157 0 0 579
Total 5,495 5,456 893 0 0 11,843
Table 4.1.8: Monthly HVAC component costs for VAV system
Figure 4.1.4 shows monthly components costs for VAV system. Table 4.1.8 and 4.1.9 represents
monthly HVAC and non-HVAC component costs associated with VAV system.
100
200
300
400
500
600
700
800
900
Cost($)
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
AirSystem Fans Cooling Heating Lights ElectricEquipment

15 | P a g e
Month
Lights
($)
Electric
Equipment
($)
Misc. Electric
($)
Misc. Fuel Use
($)
Non-HVAC Total
($)
Grand Total
($)
January 827 71 0 0 898 1,488
February 775 71 0 0 846 1,435
March 828 82 0 0 910 1,700
April 790 77 0 0 867 1,775
May 907 84 0 0 990 2,088
June 874 85 0 0 959 2,333
July 887 85 0 0 971 2,441
August 891 85 0 0 976 2,378
September 881 86 0 0 967 2,248
October 921 85 0 0 1,006 2,061
November 796 72 0 0 868 1,575
December 821 67 0 0 888 1,467
Total 10,197 950 0 0 11,147 22,990
Table 4.1.9: Monthly non-HVAC component costs for VAV system
Figure 4.1.5: Monthly energy costs for VAV system
200
400
600
800
1000
1200
1400
Cost($)
Month
HVACElectric HVACNatural Gas Non-HVACElectric

16 | P a g e
Month
Electric
($)
Natural Gas
($)
Fuel Oil
($)
Propane
($)
Remote Hot
Water
($)
Remote
Steam
($)
Remote
Chilled Water
($)
January 433 157 0 0 0 0 0
February 437 152 0 0 0 0 0
March 677 113 0 0 0 0 0
April 806 102 0 0 0 0 0
May 1,098 0 0 0 0 0 0
June 1,373 0 0 0 0 0 0
July 1,469 0 0 0 0 0 0
August 1,402 0 0 0 0 0 0
September 1,281 0 0 0 0 0 0
October 956 100 0 0 0 0 0
November 596 112 0 0 0 0 0
December 422 157 0 0 0 0 0
Total 10,950 893 0 0 0 0 0
Table 4.1.10: Monthly HVAC energy costs for VAV system
Month
Electric
($)
Natural Gas
($)
Fuel Oil
($)
Propane
($)
Remote Hot
Water
($)
Remote Steam
($)
January 898 0 0 0 0 0
February 846 0 0 0 0 0
March 910 0 0 0 0 0
April 867 0 0 0 0 0
May 990 0 0 0 0 0
June 959 0 0 0 0 0
July 971 0 0 0 0 0
August 976 0 0 0 0 0
September 967 0 0 0 0 0
October 1,006 0 0 0 0 0
November 868 0 0 0 0 0
December 888 0 0 0 0 0
Total 11,147 0 0 0 0 0
Table 4.1.11: Monthly non-HVAC energy costs for VAV system
Figure 4.1.5 represents monthly energy cost associated with VAV rooftop system. Table 4.1.10 and 4.1.11
stand for monthly HVAC and non-HVAC energy costs associated with VAV system. All costs are in USD.

17 | P a g e
4.2 Results of scenario 2: VVT System vs. VRF System:
DESIGN COOLING(VVT) DESIGN COOLING(VRF)
COOLING DATA AT Mar 1500 COOLING DATA AT Jul 1400
COOLING OA DB / WB 94.0 °F / 61.8 °F COOLING OA DB / WB 109.3 °F / 69.8 °F
Window & Skylight Solar Loads 420 ft² 10830 - 420 ft² 8150 -
Wall Transmission 11415 ft² 7582 - 11415 ft² 13124 -
Roof Transmission 9840 ft² 23972 - 9840 ft² 34238 -
Window Transmission 420 ft² 2008 - 420 ft² 4087 -
Skylight Transmission 0 ft² 0 - 0 ft² 0 -
Door Loads 40 ft² 922 - 40 ft² 1001 -
Floor Transmission 10560 ft² 0 - 10560 ft² 0 -
Overhead Lighting 60383 W 159711 - 60383 W 157330 -
Task Lighting 6226 W 18590 - 6226 W 18454 -
Electric Equipment 9700 W 29386 - 9700 W 29195 -
People 401 81577 110445 401 79658 110445
Safety Factor 0% / 0% 0 0 0% / 0% 0 0
>> Total Zone Loads - 334577 110445 - 345237 110445
Zone Conditioning - 378943 110445 - 390085 110445
Plenum Wall Load 0% 0 - 0% 0 -
Plenum Roof Load 0% 0 - 0% 0 -
Plenum Lighting Load 0% 0 - 0% 0 -
Return Fan Load 16875 CFM 67553 - 8925 CFM 35727 -
Ventilation Load 8160 CFM 114274 -110452 8925 CFM 266508 -85226
Supply Fan Load 16875 CFM 67553 - 8925 CFM 35727 -
Space Fan Coil Fans - 0 - - 81192 -
Duct Heat Gain / Loss 0% 0 - 0% 0 -
>> Total System Loads - 628324 -7 - 809238 25219
Central Cooling Coil - 32536 0 - 353424 0
Central Heating Coil - 0 - - 0 -
Precool Coil - 595788 0 - 456733 24992
Preheat Coil - 0 - - 0 -
>> Total Conditioning - 628324 0 - 810158 24992
Key: Positive values are clg loads Positive values are clg loads
Negative values are htg loads Negative values are htg loads
Table 4.2.1: Comparison between VVT and VRF system cooling loads
It can be seen that cooling load associated with VRF system is higher than that of VVT system.

18 | P a g e
DESIGN HEATING(VVT) DESIGN HEATING(VRF)
HEATING DATA AT DES HTG HEATING DATA AT DES HTG
HEATING OA DB / WB 34.0 °F / 28.5 °F HEATING OA DB / WB 34.0 °F / 28.5 °F
Window & Skylight
Solar Loads
420 ft² - - 420 ft² - -
Wall Transmission 11415 ft² 13787 - 11415 ft² 13787 -
Roof Transmission 9840 ft² 12696 - 9840 ft² 12696 -
Window Transmission 420 ft² 4884 - 420 ft² 4884 -
Skylight Transmission 0 ft² 0 - 0 ft² 0 -
Door Loads 40 ft² 459 - 40 ft² 459 -
Floor Transmission 10560 ft² 9801 - 10560 ft² 9801 -
Partitions 0 ft² 0 - 0 ft² 0 -
Overhead Lighting 0 0 - 0 0 -
Task Lighting 0 0 - 0 0 -
Electric Equipment 0 0 - 0 0 -
People 0 0 0 0 0 0
Safety Factor 0% 0 0 0% 0 0
>> Total Zone Loads - 41628 0 - 41628 0
Zone Conditioning - 41310 0 - 41033 0
Plenum Wall Load 0 0 - 0 0 -
Plenum Roof Load 0 0 - 0 0 -
Plenum Lighting Load 0 0 - 0 0 -
Return Fan Load 13500 CFM -55394 - 8925 CFM -35727 -
Ventilation Load 8160 CFM 332920 0 8925 CFM 368040 0
Supply Fan Load 13500 CFM -55394 - 8925 CFM -35727 -
Space Fan Coil Fans - 0 - - -81192 -
Duct Heat Gain / Loss 0% 0 - 0% 0 -
>> Total System
Loads
- 263442 0 - 256428 0
Central Cooling Coil - 0 0 - 0 0
Central Heating Coil - 215201 - - 297620 -
Precool Coil - 0 0 - -12805 0
Preheat Coil - 48224 - - 0 -
>> Total Conditioning - 263425 0 - 284816 0
Key: Positive values are htg loads Positive values are htg loads
Negative values are clg loads Negative values are clg loads
Table 4.2.2: Comparison between VVT and VRF system heating loads
Table 4.2.2 represents the comparison between VVT and VRF system heating loads.

19 | P a g e
Figure 4.2.1: Annual component cost for VVT system
Figure 4.2.2: Annual component cost for VRF system
Figure 4.2.1 and 4.2.2 are graphical representation of annual component costs associated with VVT
and VRF systems respectively.
Table 4.2.3 shows the comparison of annual component costs for VVT and VRF system. It is
clearly seen that HVAC costs associated with VRF system is lesser than that of the VVT system.
22.4%Cooling 4.0% Heating
38.7% Lights
12.5%Cooling
3.9%Heating
51.8% Lights

20 | P a g e
Component
Annual Cost Annual Cost
Percent of
Total
Percent of
Total
(VVT)($) (VRF)($) (VVT)(%) (VRF)(%)
Air System Fans 8,027 5,413 31.3 27
Cooling 5,755 2,520 22.4 12.5
Heating 1,032 788 4 3.9
Pumps 0 0 0 0
Heat Rejection Fans 0 0 0 0
HVAC Sub-Total 14,814 8,721 57.7 43.4
Lights 9,930 10,395 38.7 51.8
Electric Equipment 925 969 3.6 4.8
Misc. Electric 0 0 0 0
Misc. Fuel Use 0 0 0 0
Non-HVAC Sub-
Total
10,855 11,364 42.3 56.6
Grand Total 25,669 20,085 100 100
Table 4.2.3: Comparison of annual component costs of VVT vs VRF system
Figure 4.2.3: Annual energy cost for VVT system
53.7%HVAC Electric
4.0% HVAC Natural Gas

21 | P a g e
Figure 4.2.4: Annual energy cost for VRF system
Component
Annual Cost Annual Cost
Percent of
Total
Percent of
Total
(VVT)($) (VRF)($) (VVT)(%) (VRF)(%)
HVAC Components
Electric 13,782 8,721 53.7 43.4
Natural Gas 1,032 0 4 0
Fuel Oil 0 0 0 0
Propane 0 0 0 0
Remote Hot Water 0 0 0 0
Remote Steam 0 0 0 0
Remote Chilled Water 0 0 0 0
HVAC Sub-Total 14,814 8,721 57.7 43.4
Non-HVAC Components
Electric 10,855 11,364 42.3 56.6
Natural Gas 0 0 0 0
Fuel Oil 0 0 0 0
Propane 0 0 0 0
Remote Hot Water 0 0 0 0
Remote Steam 0 0 0 0
Non-HVAC Sub-Total 10,855 11,364 42.3 56.6
Grand Total 25,669 20,085 100 100
Table 4.2.4: Comparison of annual energy costs of VVT vs VRF system
43.4%HVAC Electric

22 | P a g e
Figure 4.2.3 and 4.2.4 represent the graphical view of annual energy costs for VVT and VRF
system. From those graphs we can see that in 4.2.4 there is no cost associated for HVAC natural
gas. That means in VRF system heating source is electric resistance. There is no provision of using
combustion of natural gas as heating source in VRF system. Further, costs for electricity is less
than that of the natural gas. So, using electric resistance will definitely cost less than natural gas.
So, it is obvious that VRF system will cost less and will be considered cost effective.
Table 4.2.4 is the basic comparison of annual energy costs for VRF and VVT systems. Again, it is
found that the annual energy costs for VRF system is less than that of VVT system.
Table 4.2.5: Comparison of annual energy consumption by system components of VVT vs VRF
In table 4.2.5, comparison between VVT and VRF system has been made for the annual energy
consumption by system components. It can be seen from the comparison results that the HVAC
annual energy consumption for VRF system is 40% less than that of the VVT system. So, here
there is significant reduction in the annual energy consumption by system components have been
seen.
Table 4.2.6 is for the comparison between the VVT and VRF system in terms of annual energy
consumption by energy source. Again, from the results of that comparison it is clearly seen that
the HVAC subtotal for VRF system is 40 less than that of the VVT system. From that comparison
it is fact that the efficiency of VRF system is higher than that of the VVT system.
Component
Site Energy Site Energy
(VVT)(kBTU) (VRF)(kBTU)
Air System Fans 5,75,988 3,70,092
Cooling 4,05,749 1,68,528
Heating 19,402 57,638
Pumps 0 0
Heat Rejection Fans 0 0
HVAC Sub-Total 10,01,139 5,96,258
Lights 7,13,442 7,13,442
Electric Equipment 66,457 66,457
Misc. Electric 0 0
Misc. Fuel Use 0 0
Non-HVAC Sub-Total 7,79,900 7,79,900
Grand Total 17,81,039 13,76,158

23 | P a g e
Component
Site Energy Site Energy
(VVT)(kBTU) (VRF)(kBTU)
HVAC Components
Electric 9,81,739 5,96,261
Natural Gas 19,402 0
Fuel Oil 0 0
Propane 0 0
Remote Hot Water 0 0
Remote Steam 0 0
Remote Chilled Water 0 0
HVAC Sub-Total 10,01,140 5,96,261
Non-HVAC Components
Electric 7,79,895 7,79,895
Natural Gas 0 0
Fuel Oil 0 0
Propane 0 0
Remote Hot Water 0 0
Remote Steam 0 0
Non-HVAC Sub-Total 7,79,895 7,79,895
Grand Total 17,81,035 13,76,156
Table 4.2.6: Comparison of annual energy consumption by energy source of VVT vs VRF
Figure 4.2.5: Monthly components cost for VVT system
100
200
300
400
500
600
700
800
900
1000
Cost($)
Month
Air System Fans Cooling Heating Lights ElectricEquipment

24 | P a g e
Figure 4.2.6: Monthly components cost for VRF system
Figure 4.2.5 and 4.2.6 represent the monthly component costs for the VVT and VRF system
respectively.
Figure 4.2.7: Monthly energy cost for VVT system
Figure 4.2.7 and 4.2.8 represent the monthly energy cost for VVT and VRF system respectively.
From those plots again it can be seen that monthly cost associated with VRF system is less than
VVT system. So, again VRF system has more advantage than VVT system. That advantage is
mainly because of the absence of natural gas as heating source and less energy consumption by
VRF system.
Even if we compare the monthly cooling cost of both systems, then VRF has less monthly cooling
cost compared to VVT.
0
100
200
300
400
500
600
700
800
900
1000
Cost($)
Month
Air System Fans Cooling Heating Lights Electric Equipment
200
400
600
800
1000
1200
1400
1600
Cost($)
Month
HVAC Electric HVAC Natural Gas Non-HVAC Electric

25 | P a g e
Figure 4.2.8: Monthly energy cost for VRF system
4.3 Results of Scenario 3: After modifying layout and schedules (VVT System):
After modifying the layout of gym and schedules following observations are made. For the purpose
of comparison VAV system of scenario 1 is considered.
DESIGN COOLING
(Before)
DESIGN COOLING
(After)
DESIGN HEATING
(Before)
DESIGN HEATING
(After)
COOLING DATA AT
Mar 1500
COOLING DATA AT
Mar 1300
HEATING DATA AT
DES HTG
HEATING DATA AT
DES HTG
COOLING OA DB /
WB 94.0 °F / 61.8 °F
COOLING OA DB / WB
91.5 °F / 60.9 °F
HEATING OA DB /
WB 34.0 °F / 28.5 °F
HEATING OA DB /
WB 34.0 °F / 28.5 °F
Sensible Latent Sensible Latent Sensible Latent Sensible Latent
ZONE
LOADS
(BTU/hr) (BTU/hr) (BTU/hr) (BTU/hr) (BTU/hr) (BTU/hr) (BTU/hr) (BTU/hr)
>> Total
Zone Loads
334577 110445 322105 110445 41628 0 42049 0
>> Total
System
Loads
605717 -9 574971 -18 128680 0 127658 0
>> Total
Conditioning
605368 0 574851 0 128680 0 127658 0
Key:
Positive values are clg
loads
Positive values are clg
loads
Positive values are htg
loads
Positive values are htg
loads
Negative values are htg
loads
Negative values are htg
loads
Negative values are clg
loads
Negative values are clg
loads
Table 4.3.1: Comparison of cooling and heating loads before and after modification (VAV system)
Here, it can be seen from the table 4.3.1 that there is reduction in the cooling and heating load of
the VAV system after modifying the layout and schedules.
600
650
700
750
800
850
900
950
1000
1050
Cost($)
Month
HVAC Electric Non-HVAC Electric

26 | P a g e
Component
Initial System
After changing
the Layout
After changing
the schedule
($) ($) ($)
Air System Fans 5,495 5,378 5,399
Cooling 5,456 5,358 5,084
Heating 893 889 916
Pumps 0 0 0
Heat Rejection Fans 0 0 0
HVAC Sub-Total 11,843 11,625 11,399
Lights 10,197 9,810 9,837
Electric Equipment 950 956 959
Misc. Electric 0 0 0
Misc. Fuel Use 0 0 0
Non-HVAC Sub-Total 11,147 10,766 10,796
Grand Total 22,990 22,391 22,194
Table 4.3.2: Comparison of Annual cost of system components (VAV System)
Component
Initial System
After changing the
layout
After changing the
schedule
($) ($) ($)
HVAC Components
Electric 10,950 10,737 10,483
Natural Gas 893 889 916
Fuel Oil 0 0 0
Propane 0 0 0
Remote CW 0 0 0
HVAC Sub-Total 11,843 11,625 11,399
Non-HVAC Components
Electric 11,147 10,766 10,796
Natural Gas 0 0 0
Fuel Oil 0 0 0
Remote Steam 0 0 0
Non-HVAC Sub-Total 11,147 10,766 10,796
Grand Total 22,990 22,391 22,194
Table 4.3.3: Comparison of Annual cost of energy (VAV System)
Table 4.3.2 and 4.3.3 represent the comparison of annual energy cost associated with system
components and energy. Results show that there is a saving of almost 800$ for the system
components and energy. That saving in the cost annually can be considered as good observation
for that school.

27 | P a g e
Component
Site Energy Site Energy Site Energy
(kBTU)
Initial system
(kBTU)
After layout change
(kBTU)
After change in
schedule
Air System Fans 3,83,486 3,72,801 3,73,223
Cooling 3,76,457 3,67,473 3,47,551
Heating 9,161 8,861 10,858
Pumps 0 0 0
Heat Rejection Fans 0 0 0
HVAC Sub-Total 7,69,104 7,49,135 7,31,631
Lights 7,13,442 6,81,521 6,81,521
Electric Equipment 66,457 66,457 66,457
Misc. Electric 0 0 0
Misc. Fuel Use 0 0 0
Non-HVAC Sub-Total 7,79,900 7,47,978 7,47,978
Grand Total 15,49,004 14,97,114 14,79,609
Table 4.3.4: Comparison of energy consumption by system component (VAV System)
Component
Site Energy Site Energy Site Energy
(kBTU)
Initial system
(kBTU)
After layout change
(kBTU)
After change in schedule
HVAC Components
Electric 7,59,945 7,40,275 7,20,775
Natural Gas 9,161 8,861 10,858
Fuel Oil 0 0 0
Propane 0 0 0
Remote Steam 0 0 0
HVAC Sub-Total 7,69,106 7,49,136 7,31,632
Non-HVAC Components
Electric 7,79,895 7,47,974 7,47,974
Natural Gas 0 0 0
Fuel Oil 0 0 0
Propane 0 0 0
Non-HVAC Sub-Total 7,79,895 7,47,974 7,47,974
Grand Total 15,49,000 14,97,110 14,79,606
Table 4.3.5: Comparison of energy consumption by energy source (VAV System)
Table 4.3.4 and 4.3.5 stand for the annual energy consumption of VAV system for system
components and energy source respectively. It can be seen that because of this modification almost
69000 kBTU energy can be saved annually.

28 | P a g e
5. CONCLUSIONS AND RECOMMENDATIONS:
For the proposed layout of primary school located in Phoenix, Arizona energy modelling was done
using rooftop units of VAV system.
In scenario 2, comparison between VVT system and VRF system was done. Though VRF system
has more cooling and heating load compared to VVT system, annual energy consumption as well
as annual cost associated with system is low for VRF system compared to VVT system.
From scenario 3, it can be concluded that by changing the orientation of gym and changing the
schedules, energy consumption and annual costs can be significantly reduced for VAV system.
Results show that there is a saving of almost 800$ for the system components and energy. Also,
69000 kBTU energy can be saved.
REFERENCES:
1. https://www.carrier.com/commercial/en/us/software/hvac-system-design/hourly-analysis-
program/
2. Hourly Analysis Program Quick Reference Guide by CARRIER.
3. Energy Design Guidelines for High Performance Schools for Hot and Dry climates.
4. http://articles.extension.org/pages/58540/considerations-for-selecting-energy-efficient-
windows-for-homes-in-different-climates
5. Technical Guidance Document TGD-022 by Planning & Building Unit Department of
Education and Skills Tullamore, Co. Offaly.
6. Selecting windows for energy efficiency by U.S. Department of Energy.
7. McQuiston et al., ”Analysis and Design of Heating, Ventilating and Air Conditioning”, sixth
edition.
8. Utility rates and fess-FY 2015/2016 mesa-az.
9. http://georgebrazilhvac.com/blog/gas-vs-electric-heat-in-phoenix-which-is-cheaper-to-run

29 | P a g e
List of Tables:
Table
No.
Name
Page
No.
4.4.1 Design heating and cooling load with VAV system 7
4.1.2 Air system simulation report of VAV rooftop system 9
4.1.3 Monthly air system simulation report 9
4.1.4 Annual component cost for VAV system 10
4.1.5 Annual energy cost for VAV system 11
4.1.6 Energy consumption by system component for VAV system 12
4.1.7 Energy consumption by energy source for VAV system 13
4.1.8 Monthly HVAC component costs for VAV system 14
4.1.9 Monthly non-HVAC component costs for VAV system 15
4.1.10 Monthly HVAC energy costs for VAV system 16
4.1.11 Monthly non-HVAC energy costs for VAV system 16
4.2.1 Comparison between VVT and VRF system cooling loads 17
4.2.2 Comparison between VVT and VRF system heating loads 18
4.2.3 Comparison of annual component costs of VVT vs VRF system 20
4.2.4 Comparison of annual energy costs of VVT vs VRF system 21
4.2.5 Comparison of annual energy consumption by system components of VVT vs VRF 22
4.2.6 Comparison of annual energy consumption by energy source of VVT vs VRF 23
4.3.1 Comparison of cooling and heating loads before and after modification (VAV system) 25
4.3.2 Comparison of Annual cost of system components (VAV System) 26
4.3.3 Comparison of Annual cost of energy (VAV System) 26
4.3.4 Comparison of energy consumption by system component (VAV System) 27
4.3.5 Comparison of energy consumption by energy source (VAV System) 28

30 | P a g e
List of Figures:
Figure No. Name Page No.
3.1 First Floor 3
3.2 Second Floor 3
3.3 Third Floor 4
3.3.1 Modified layout of gym 5
4.1.1 Psychrometric analysis for VAV rooftop system 8
4.1.2 Annual component costs for VAV system 10
4.1.3 Annual energy cost for VAV system 11
4.1.4 Monthly component costs for VAV system 14
4.1.5 Monthly energy costs for VAV system 15
4.2.1 Annual component cost for VVT system 19
4.2.2 Annual component cost for VRF system 19
4.2.3 Annual energy cost for VVT system 20
4.2.4 Annual energy cost for VRF system 21
4.2.5 Monthly components cost for VVT system 23
4.2.6 Monthly components cost for VRF system 24
4.2.7 Monthly energy cost for VVT system 24
4.2.8 Monthly energy cost for VRF system 25

31 | P a g e
APPENDICES:
1. Wall construction[3]:
Outside Surface Color Dark
Absorptivity 0.90
Overall U-value 0.034 BTU/(hr-ft2-F)
Thick
ness
Density
Specific
Ht.
R-Value Weight
Layers in lb/ft³
BTU / (lb
- °F)
(hr-ft²-
°F)/BTU
lb/ft²
Inside surface resistance 0.000 0.0 0.00 0.68500 0.0
5/8-in gypsum board 0.625 50.0 0.26 0.56004 2.6
R-25 batt insulation 8.000 0.5 0.20 25.64103 0.3
steel studs 2.500 0.0 0.00 0.91000 0.0
Air space 0.100 0.0 0.00 0.91000 0.0
4-in HW concrete 4.000 140.0 0.20 0.33333 46.7
4-in face brick 4.000 125.0 0.22 0.43290 41.7
Outside surface resistance 0.000 0.0 0.00 0.33300 0.0
Totals 19.225 - 29.80530 91.3
2. Window construction[6]:
Detailed Input Yes
Height 5.00 ft
Width 3.00 ft
Frame Type Wood
Internal Shade Type Vertical Blinds
Overall U-Value 0.323 BTU/(hr-ft²-°F)
Overall Shade Coefficient 0.388
Gap Type 1/2" Argon
Outer Glazing 1/4" clear low-e
Glazing #2 1/4" clear low-e
3. Roof Construction[3]:
Outside Surface Color Dark
Absorptivity 0.90
Overall U-value 0.034 BTU/(hr-ft2-F)

32 | P a g e
Thickness Density Specific Ht. R-Value Weight
Layers in lb/ft³
BTU / (lb -
°F)
(hr-ft²-
°F)/BTU
lb/ft²
Inside surface resistance 0.000 0.0 0.00 0.68500 0.0
22 gage steel deck 0.034 489.0 0.12 0.00011 1.4
R-25 batt insulation 8.000 0.5 0.20 25.64103 0.3
Air space 0.000 0.0 0.00 0.91000 0.0
Built-up roofing 0.375 70.0 0.35 0.33245 2.2
Outside surface resistance 0.000 0.0 0.00 0.33300 0.0
Totals 8.409 - 27.90158 3.9
4. Doors and Shades:
Gross Area 40.0 ft²
Door U-Value 0.270 BTU/(hr-ft²-°F)
Glass Area 28.0 ft²
Glass U-Value 0.340 BTU/(hr-ft²-°F)
Glass Shade Coefficient 0.350
Glass Shaded All Day? No
Shade reveal depth 6.00 in
5. Electric and Natural gas rates:
 Electric Rates[8]:
Customer charge: 53 $
Minimum charge: 53 $
Step Type Season Period Block Size Block Units $/kWh
Energy Winter All Periods 15000 kWh 0.05375
Energy Summer All Periods 15000 kWh 0.06491
 Gas Rate[9]:
Customer charge: 64 $
Minimum charge: 64 $
Step Type Season Period Block Size Block Units $/Therm
Fuel All Seasons All Periods 9999999 Therm 1.36000
6. Occupancy: 400 Students
7. Building weight: 100 lb/ft2

Energy modelling of a three-story primary school building located in Phoenix, Arizona

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Energy modelling of a three-story primary school building located in Phoenix, Arizona

Similar to Energy modelling of a three-story primary school building located in Phoenix, Arizona (20)

Energy modelling of a three-story primary school building located in Phoenix, Arizona