The paper presents two case studies, a commercial & a community project, in Houston Texas, where energy simulation and a decision matrix were used to solve budget conflicts and meet LEED EA-1 requirements. The first case study consists of the analysis of three different direct-expansion (DX) systems in an underfloor air distribution (UFAD) configuration for an office building with an unusually large footprint. Of the three options, only two could meet EA-1 pre-requisite for LEED-NC certification while meeting the project budget. The second case study involves analysis of a 120,000 sf. Community recreation center with multiple space types and operation schedules. The analysis employed different combinations of energy recovery systems, efficient lighting package, skylights and large efficient ceiling fans. While all the options met LEED-NC EA-1 prerequisite, each had a different payback time. Finally a combination of strategies was used for optimum payback and energy efficiency

McLean, D.

Upadhyaya, K.

Texas A&M University

1 
CASE STUDIES OF SYSTEMS INTEGRATION THROUGH ENERGY SIMULATION 
DURING EARLY DESIGN PHASE 
      Kapil Upadhyaya             David McLean   
      Energy modeler             Project Manager    
      Kirksey              CHPA    
      kapilu@kirksey.com,              dmaclean@chpengr.com,    
_____________________________________________________________________________________________ 
 
ABSTRACT 
The paper presents two case studies, a commercial & 
a community project, in Houston Texas, where 
energy simulation and a decision matrix were used to 
solve budget conflicts and meet LEED EA-1 
requirements. The first case study consists of the 
analysis of three different direct-expansion (DX) 
systems in an underfloor air distribution (UFAD) 
configuration for an office building with an unusually 
large footprint. Of the three options, only two could 
meet EA-1 pre-requisite for LEED-NC certification 
while meeting the project budget. The second case 
study involves analysis of a 120,000 sf. community 
recreation center with multiple space types and 
operation schedules. The analysis employed different 
combinations of energy recovery systems, efficient 
lighting package, skylights and large efficient ceiling 
fans. While all the options met LEED-NC EA-1 
prerequisite, each had a different payback time. 
Finally a combination of strategies was used for 
optimum payback and energy efficiency. 
INTRODUCTION  
Selecting the appropriate building design, in today’s 
market of multiple best “Green” technologies, 
depends on early identification and integration of 
systems through a coordinated effort by the client, 
architect, engineer and contractor during the 
schematic design phase. It is the intent of this paper 
to show how the analysis tools and processes used, 
aided in the decision process.  
CASE STUDY 1 
The core and shell building consisted of three pods for 
office spaces in Houston, each of 112,500 sf. and three 
floors high, connected by lobbies on two floors; the first 
floor lobby was double height. Figure 1 shows the Equest 
image of the proposed building. The project goal was to 
achieve LEED-CS silver rating. At the end of schematic 
design (SD) phase when the architectural design was 
finalized, a decision on HVAC system was to be made 
incumbent upon the fact that the system selected should 
be able to meet the LEED prerequisite of 14% energy 
 
 
efficiency over ASHRAE 2004 baseline building.  
For a building of this size, a chilled-water system 
would be a typical choice. While a chilled-water 
system could meet the 14% requirement in Houston, 
as demonstrated in Biesterveld[1] et al., there was a 
significant investment savings if DX units were 
selected. Additionally, there is research demystifying 
the dehumidification effectiveness of a chilled-water 
system over DX units; for example, Browning[2] 
discusses a method to estimate and hence effectively 
use dehumidification for comfort cooling with correct 
sizing of low cost DX equipment in hot and humid 
climates.  
 
 
Figure 1. Equest image of office building. 
 
Following these, three representative DX units were 
selected for performing energy analysis. The office 
areas were designed for underfloor air distribution 
while the lobbies were served by traditional mixed-
ventilation system. A baseline energy model was 
built conforming to Appendix G, ASHRAE 2004. 
Table 1 shows the envelope design data used for the 
purpose. Table 2 shows envelope design data for the 
proposed building envelope. 
 
 
 
 
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2 
Table 1. Envelope design data for baseline building.
  
 
Specifications for Base Case according to ASHRAE 2004 Appendix-G 
  Building components  Assembly Max Insulation Min. R-value 
 
GROUND FLOOR / 
SLAB ON GRADE  Unheated Slab on Grade NR 
INTERMEDIATE / 
INTERSTITIAL FLOORS  NR 
 
EXTERNAL WALL 
Mass walls 
R-13 Batt insulation  U-0.124 R-13 
INTERNAL WALL NR 
ROOF 
Insulation entirely above deck
3/8" Built Up Roofing 
R-19 Insulation 
Steel Frame 24”oc U-0.063 R-19 
Reflectivity 0.3  
VERTICAL 
FENESTRATION   Assembly Max U-value Assembly Max SHGC 
 
Vertical glazing 437.2% 
WWAR 1.22 
SHGC - 0.17 
SHGC(N) - 0.61 
SKY-LIGHTS None 
SHADING None 
  
Table 2. Envelope design data for proposed building. 
  Specifications for the Proposed Design Building  
  Building Envelope components used by  simulation model U-value 
 
GROUND FLOOR / SLAB 
ON GRADE 9inch concrete unheated slab on Grade NR 
INTERMEDIATE / 
INTERSTITIAL FLOORS NR 
EXTERNAL WALL 
 
Mass Wall ; 10” Concrete Tilt Walls ; Internal Batt Insulation  R-
13  R-13 insulation 
INTERNAL WALL NR 
ROOF 
Insulation entirely above deck ; R19 Thermoplastic Membrane 
Roofing 1 ½” Galvanized Sheet R-19 insulation 
Reflectance 0.3 Reflectance 0.3 
VERTICAL 
FENESTRATION  Assembly Max U-value Assembly Max SHGC 
 
Type 1  
Type 2 
0.29; 0.29 
Solarscreen VRE Insulating Glass 
Daylighting controls simulated in the the 
two lobbies only. 
0.30; 0.30 
SKY-LIGHTS None 
SHADING Shading per design / drawing  (Overhangs on South and East) 
 
 
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Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 2008
3 
 
Table 3. Lighting design data for baseline building and proposed building 
 
 
Table 4. HVAC design data for baseline building and proposed building. 
HVAC System Definition 
  
  
  
Cooling Source 
BASELINE BUILDING PROPOSED BUILDING 
Chilled Water Coils DX Coils 
Heating Source Electric Resistance Electric Resistance 
System Type Packaged VAV with PFP boxes 
Packaged VAV Rooftop units with 
perimeter underfloor boxes 
System per Area 2 Systems per Floor 2 Systems per Floor 
 
Return Air Path Plenum Plenum 
 Seasonal Thermostat Set points 
  
  
  
Occupied     
Cool
Heat 
74 
72 
74 
72 
Unoccupied     
Cool
Heat 
74 
72 
74 
72 
 Design Temperatures 
  
  
  
Cooling Design 
Temp     
Indoor
Supply 
74 
54 
74 
63 
Heating Design 
Temp     
Indoor
Supply 
72 
92 
72 
85 
Air Flows 
  
Minimum Design 
Flow 0.40 cfm/sqft 0.65 cfm/sqft 
VAV Minimum 
Flow 30% 30% 
 Supply Fans Power & Mtr Eff 
2.4 in.WG for offices, 3.5 in. WG for 
lobbies; High efficiency 
2.4 in.WG for offices, 3.5 in. WG 
for lobbies; High efficiency 
  
HVAC ZONE HEATING, VENT & 
ECONOMIZERS  
 
Zone Heat Sources & Capacities 
Fan Type Variable Speed Drive Variable Speed Drive 
Baseboards None None 
Heat/ Reheat 
Electric   30 F 30F 
DOE-2.1E Command / 
Keyword BASELINE  BUILDING PROPOSED  BUILDING 
Input 
Description 
 
OFFICE SPACE INPUT SOURCE INPUT SOURCE   
LIGHTING-W/SQFT 
1.1-office, 0.5- 
corridor, 1.5-elect. 
Room, 0.9-
Restroom, 1.1-
Lobby, 0.15-
Exterior,1.1-Copy 
Rm. 
From: 
ASHRAE 
2004 Table 
9.5.1 Pg 64 
1.1-office, 0.5- corridor, 
1.5-elect. Room, 0.9-
Restroom, 1.1-Lobby, 
0.15-Exterior,1.1-Copy 
Rm. 
From: 
ASHRAE 
2004 Table 
9.5.1 Pg 64 W/SQFT 
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Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 2008
4 
 
UNDERFLOOR SYSTEM IN EQUEST 
 
Equest does not have algorithms to simulate air-flow and 
hence displaced ventilation systems. So a method 
suggested in HVAC Simulation Guidelines [3] was 
adopted which consists of distributing occupant, lighting 
and equipment power to the thermal zone and an 
overhead return plenum; this would approximately 
represent stratification of air and hence cooling load 
attributed to the thermal zone and return plenum. 
Table 4 shows a sample zone with the redistribution 
of power densities. Additionally, to account for latent 
cooling loads the coil-bypass factor was increased so 
as to simulate air leaving the coil at 53ºF while the 
mixed-air leaving the AHU at 65ºF. 
 
Table 5. Distribution of power densities in baseline building and proposed building.
 
 
EL1(BASELINE) 
 
Perimeter 
 
Core 
 
Perimeter 
 
Core 
 
Perimeter 
 
Core 
OPD 137 230 200 193 200 193 
LPD 1.11 1.08 1.11 0.99 1.11 0.99 
EPD 1.186 1.151 2 1.377 2 1.377 
 
EL1(PROPOSED) 
   
OPD 183 307 267 257 267 257 
LPD 0.74 0.72 0.74 0.66 0.74 0.66 
EPD 0.79 0.77 1.34 0.92 1.34 0.92 
OCCUPANT DENSITY FOR PLENUM:  
SPACE AREA O.P.D. O.PD./AREA 
EL1 West Perim Spc (G.W1) 1575 183 0.1162 2058 
EL1 South Perim Spc (G.S2) 4529 183 0.0404 5919 
EL1 East Perim Spc (G.E3) 1574 183 0.1162 2058 
EL1 North Perim Spc (G.N4) 4380 183 0.0418 5724 
EL1 Core Spc (G.C5) 25327 307 0.0121 33100 
∑AREA PER PERSON/AREA OF 
SPACE   0.3267  
AREA OF PLENUM   37385  
AREA PER PERSON (PLENUM)   489  
LIGHTING POWER DENSITY FOR PLENUM: 
 
EQUIPMENT POWER DENSITY FOR 
PLENUM: 
L.P.D. L.P.D.*AREA  E.P.D. E.P.D.*AREA 
0.74 1166 
 
 0.79 1244 
0.74 3352  0.79 3578 
0.74 1165  0.79 1244 
0.74 3241  0.79 3460 
0.72 18235  0.77 19502 
Condenser Type  Air Cooled Air Cooled 
Cooling EER/COP 6.1 COP 
9.4 EER – System 1 
11.4 EER – System 2 
12.3 EER – System 3 
Heating Zonal Heating and Reheating Only 
Zonal Heating  and  Reheating 
Only 
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∑AREA L.P.D.*AREA OF SPACE 27159 
∑AREA E.P.D.*AREA 
OF SPACE  29028 
AREA OF PLENUM 37385 AREA OF PLENUM  37385 
LIGHTING POWER 
DENSITY(PLENUM) 0.24 
EQUIPMENT POWER 
DENSITY(PLENUM)  0.26 
 
0
200000
400000
600000
800000
1000000
1200000
1400000
1600000
1800000
LIGHTS EQUIPMENT HEATING COOLING HEAT
REJECTION
PUMPS FANS HOT WATER
Energy types
A
nn
ua
l e
ne
rg
y 
co
ns
um
pt
io
n 
(k
W
h)
LEED
BASELINE
SYSTEM 1
SYSTEM 2
SYSTEM 3
Figure 2. Comparison of annual energy types for all systems. 
 
 
The annual cost of electricity for the baseline 
building at 10cents/kWh, was $584436 as compared 
to $530808 for System 1 (refer Table 4 for individual 
system description), $497659 for System 2, and 
$486211 for System 3. This corresponds to 9.18% for 
System 1, 14.85% for System 2, and 16.8% for 
System 3. Evidently, System 2 and System 3 would 
be able to meet the LEED prerequisite of 14%.   
 
Figure 3. Comparison of annual cost of energy. 
 
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Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 2008
6 
System 2 was finally selected for the project and later, 
in the value engineering phase, the same energy model 
was used to determine effects of changing glazing and 
shading devices.  
 
CASE STUDY 2 
The five floor community building consisted of children 
play areas and training rooms on first and second floors; 
swimming and therapy pools on the third floor; gym, 
workouts and running track on fourth and fifth floors. 
 
 
Figure 5. Equest image of community building. 
 
The project goal was to look at all possible energy 
efficient strategies and estimate payback costs in the SD 
phase. A LEED-baseline-building energy-model was 
created per Appendix G, ASHRAE 2004; energy-
recovery with heat pipe was implemented per code 
requirements. A proposed-building energy-model was 
created with chilled-water system and heat pipe for 
energy recovery. Table 5 lists the system description of 
the proposed building. Parametric variations of this 
were created with the following energy efficient 
features: 
1. Big ceiling fans in all workout areas to reduce total 
static pressure in ducts by 1in. wg. & increase 
thermostats by 4°F. This was based on a study (James 
et al.) which estimates a reduction of 2-6°F in space 
temperatures with the use of ceiling fans. An external 
scheduled load was added to the energy model to 
represent the fan load. 
2. Shading on the north-west with vertical fins to 
block direct sunlight and glare. Shading studies 
were carried in Ecotect to determine optimum 
depths and spacing. 
3. Daylighting controls using stepped-dimming at 
perimeter to harvest daylight and save energy (30fc 
setpoint). 
4. Efficient lighting package to include a 20% 
reduction in lighting power density over ASHRAE 
2004 with stepped lighting controls.  
5. Five skylights on the fifth floor to harvest daylight. 
6. Solar hot water system for therapy pool. 
7. Energy Recovery Unit (ERU) with desiccant wheel 
to treat outside air - Trane Energy Wheel S2500 H, 
767,791btu/hr total capacity; Trane CDQ Dessicant 
Wheel -  137.6lb/hr water vapor transfer, -
199,058btu/hr heat transfer capacity.  
Enthalpy Wheel type- recovering both sensible and 
latent heat; Operating mode - both heat/cool; Make 
up air temperature control- mixed Air Reset; 
Capacity Control- bypass OA; Operation-OA exhaust 
DT; OA/Exhaust DT- 5°F. 
8. Systems 1-7 combined. This option combines of 
the above mentioned options from 1 to 7 in a single 
building.  
9. Option 8 with reduction in chiller capacity by 40 
ton. This was an approximate reduction in chiller 
capacity modeled with reduction in loads due to all 
the above strategies. 
10. Option 9 with shading removed. This was done to 
compare payback time of all other strategies without 
the most expensive option of external shading device. 
Option 10 turned out to be the most cost-effective.  
11. Option 10 with ceiling fans and efficient lighting 
removed. 
  
 
 
 
 
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Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 2008
7 
Table 6. HVAC design data for the proposed community building.
 
SYSTEM TYPE 1 
(floor 1) 
SYSTEM TYPE 2 
(floor2,4,5) 
SYSTEM TYPE 3 
(floor 3) 
Temperature 
75 F Summer          
72 F Winter 
75 F Summer  72 F 
Winter 
     Pool            
82 F Summer        
82 F Winter 
People-schedule A A B 
Area/person 150 50 300 
People-heat gain-latent 200 625 500 
People-heat gain-sensible 250 375 340 
HVAC SYSTEM DESCRIPTION    
 
Equipment type Chilled water coils with water cooled condensers 
Cooling Source Chilled water coils Chilled water coils Chilled water coils 
Heating Source Electric resistance Electric resistance Electric resistance 
System Type 
Series powered VAV 
with elec. Reheat 
Series powered 
VAV with elec. 
Reheat 
Single Zone Air 
Handler with Elec. 
Heat 
Return Air Path Plenum Plenum Ducted 
Occupied    
Cool 75 72 82 
Heat 72 70 82 
Unoccupied    
Cool 85 85 82 
Heat 55 55 82 
 Design Temperatures    
Cooling Design Temp    
Indoor 75 75 82 
Supply 56 56 60 
Heating Design Temp    
Indoor 72 72 72 
Supply 85 to 95 85 to 95 95 
Air Flows  
Minimum Design Flow 0.75 cfm/sqft 0.75 cfm/sqft 1 cfm/sqft 
VAV Minimum Flow 30% primary flow 30% primary flow 
100% perimeter 
100% core 
HVAC SYSTEM FANS    
 Supply Fans    
Power & Mtr Eff 3.5 in.WG, High 3.5 in.WG, High 3.5 in.WG, High 
Fan Type Variable Speed Drive Variable Speed Drive Constant Vol 
Heat Reheat Electric  30F 30F 30F 
CHILLED WATER SYSTEM  
Pump Configuration Single system pumps, variable primary flow 
Number of System Pumps 1 
CHW Loop Flow 
 Constant speed 
Pump Control VFD/VSD 
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Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 2008
8 
Loop Pump Motor Efficiency Premium (93% ) 
Chiller Type Electric Centrifugal Hermetic 
Condenser Type Water Cooled 
Compressor Type 
 Constant Speed 
Number & size 2, 200-400 TONS 
Chiller Efficiency 0.50 kW/ton 
WATER COOLED CONDENSOR / 
COOLING TOWER  
Condenser Configuration Open Tower 
Temperature Control Fixed 
Setpoint 86F 
Capacity Control variable speed fans 
Chilled Water Setpoint Type OA Reset 
CHW Min Temp 42F 
CHW Max Temp 58F 
Operation Stand-by 
 
 
One shortcoming of the simulations was the inability 
to model thermal mass of pool-water. Another 
approximation lies in the inability of Equest to 
integrate a separate outside-ahu with each floor-ahu 
in Equest. To overcome this, dummy zones were 
created with ‘0’ loads; OAHUs were assigned to 
these with energy-recovery capacities per design. 
Each floor-ahu was then assigned to draw outside-air 
from these.  
Figure 5 compares the annual cost savings due to the 
individual energy efficient strategies, the respective 
investment, payback time, cumulative income in 
twenty-five years and the LEED points earned by 
each option.  
 
 
 
 
 
 
 
 
 
 
It could be seen that the proposed building was able 
to meet the LEED 2.2 pre-requisite of 14% with the 
chilled water system. Among individual strategies, 
skylights give the fastest payback followed by 
energy-recovery unit with vapor wheel. Efficient 
lighting, ceiling fans and perimeter daylight controls 
follow next. The external shading devices considered 
for this project remain  unprofitable due to cost and 
orientation of the building. Combination of all the 
strategies without the shading device could achieve a 
payback of 3.1 years. 
ESL-HH-08-12-38
Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 2008
9 
 
 
Figure 5. Cost savings for different energy saving strategies.  
 
CONCLUSIONS 
Energy modeling done in the early design phase 
helps in making significant decisions during the 
design process like effects of changing glazing, 
shading devices, operation schedules and 
lighting/equipment efficiencies. It also helps in 
making decisions on HVAC systems and testing 
atypical technologies which need integration in 
buildings at the SD phase like energy recovery, 
skylights and daylighting controls.  Simulations at 
this stage come with assumptions with regards to 
details of systems and sometimes architectural 
 
 
design, but are nevertheless useful. 
REFERENCES 
ASHRAE 2004. ANSI/ASHRAE/IESNA Standard 90.1-
2004. Energy Standard for Buildings Except Low-rise 
Residential Building. Atlanta: American Society of 
Heating, Refrigerating and Air-Conditioning Engineers, 
Inc. 
Biesterveld M., Harshaw J., Murphy J., 2008. Energy-
saving strategies for LEED Energy and Atmosphere 
Credit 1. Trane Engineers newsletter, volume 37-2, 2008.  
ESL-HH-08-12-38
Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 2008
10 
Browning, B. K., 2002. Direct Expansion Air 
Conditioning System Selection for Hot & Humid  
Climates. Proceedings of Thirteenth Symposium on 
Improving Building Systems in Hot and Humid 
Climates. 
James. P., J. Sonne. R. Vieira, D. Parker, and M. 
Anello. 1996. "Are Energy Savings Due to Ceiling 
Fans Just Hot Air?'Proceedinas of the ACEEE 
Summer Studv on Enerw Efficiency in Buildings, 
8:89-93. American Council for an Energy-Efficient 
Economy, Washington D.C.  
ACKNOWLEDGEMENT 
The authors would like to thank Brian Malarkey, 
Kirksey for his initiative that made research into 
these two projects possible; and Jonthan Curtin, 
Wylie Associates, for technical help.  
ESL-HH-08-12-38
Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 2008


English

Case Studies of Systems Integration through Energy Simulation During Early Design Phase

Texas A&amp;M Repository

1 CASE STUDIES OF SYSTEMS INTEGRATION THROUGH ENERGY SIMULATION DURING EARLY DESIGN PHASE       Kapil Upadhyaya             David McLean         Energy modeler             Project Manager          Kirksey              CHPA          kapilu@kirksey.com,              dmaclean@chpengr.com,    _____________________________________________________________________________________________  ABSTRACT The paper presents two case studies, a commercial & a community project, in Houston Texas, where energy simulation and a decision matrix were used to solve budget conflicts and meet LEED EA-1 requirements. The first case study consists of the analysis of three different direct-expansion (DX) systems in an underfloor air distribution (UFAD) configuration for an office building with an unusually large footprint. Of the three options, only two could meet EA-1 pre-requisite for LEED-NC certification while meeting the project budget. The second case study involves analysis of a 120,000 sf. community recreation center with multiple space types and operation schedules. The analysis employed different combinations of energy recovery systems, efficient lighting package, skylights and large efficient ceiling fans. While all the options met LEED-NC EA-1 prerequisite, each had a different payback time. Finally a combination of strategies was used for optimum payback and energy efficiency. INTRODUCTION  Selecting the appropriate building design, in today’s market of multiple best “Green” technologies, depends on early identification and integration of systems through a coordinated effort by the client, architect, engineer and contractor during the schematic design phase. It is the intent of this paper to show how the analysis tools and processes used, aided in the decision process.  CASE STUDY 1 The core and shell building consisted of three pods for office spaces in Houston, each of 112,500 sf. and three floors high, connected by lobbies on two floors; the first floor lobby was double height. Figure 1 shows the Equest image of the proposed building. The project goal was to achieve LEED-CS silver rating. At the end of schematic design (SD) phase when the architectural design was finalized, a decision on HVAC system was to be made incumbent upon the fact that the system selected should be able to meet the LEED prerequisite of 14% energy   efficiency over ASHRAE 2004 baseline building.  For a building of this size, a chilled-water system would be a typical choice. While a chilled-water system could meet the 14% requirement in Houston, as demonstrated in Biesterveld[1] et al., there was a significant investment savings if DX units were selected. Additionally, there is research demystifying the dehumidification effectiveness of a chilled-water system over DX units; for example, Browning[2] discusses a method to estimate and hence effectively use dehumidification for comfort cooling with correct sizing of low cost DX equipment in hot and humid climates.    Figure 1. Equest image of office building.  Following these, three representative DX units were selected for performing energy analysis. The office areas were designed for underfloor air distribution while the lobbies were served by traditional mixed-ventilation system. A baseline energy model was built conforming to Appendix G, ASHRAE 2004. Table 1 shows the envelope design data used for the purpose. Table 2 shows envelope design data for the proposed building envelope.     ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 20082 Table 1. Envelope design data for baseline building.   Specifications for Base Case according to ASHRAE 2004 Appendix-G   Building components  Assembly Max Insulation Min. R-value  GROUND FLOOR / SLAB ON GRADE  Unheated Slab on Grade NR INTERMEDIATE / INTERSTITIAL FLOORS  NR  EXTERNAL WALL Mass walls R-13 Batt insulation  U-0.124 R-13 INTERNAL WALL NR ROOF Insulation entirely above deck3/8" Built Up Roofing R-19 Insulation Steel Frame 24”oc U-0.063 R-19 Reflectivity 0.3  VERTICAL FENESTRATION   Assembly Max U-value Assembly Max SHGC  Vertical glazing 437.2% WWAR 1.22 SHGC - 0.17 SHGC(N) - 0.61 SKY-LIGHTS None SHADING None   Table 2. Envelope design data for proposed building.   Specifications for the Proposed Design Building    Building Envelope components used by  simulation model U-value  GROUND FLOOR / SLAB ON GRADE 9inch concrete unheated slab on Grade NR INTERMEDIATE / INTERSTITIAL FLOORS NR EXTERNAL WALL  Mass Wall ; 10” Concrete Tilt Walls ; Internal Batt Insulation  R-13  R-13 insulation INTERNAL WALL NR ROOF Insulation entirely above deck ; R19 Thermoplastic Membrane Roofing 1 ½” Galvanized Sheet R-19 insulation Reflectance 0.3 Reflectance 0.3 VERTICAL FENESTRATION  Assembly Max U-value Assembly Max SHGC  Type 1  Type 2 0.29; 0.29 Solarscreen VRE Insulating Glass Daylighting controls simulated in the the two lobbies only. 0.30; 0.30 SKY-LIGHTS None SHADING Shading per design / drawing  (Overhangs on South and East)   ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 20083  Table 3. Lighting design data for baseline building and proposed building   Table 4. HVAC design data for baseline building and proposed building. HVAC System Definition       Cooling Source BASELINE BUILDING PROPOSED BUILDING Chilled Water Coils DX Coils Heating Source Electric Resistance Electric Resistance System Type Packaged VAV with PFP boxes Packaged VAV Rooftop units with perimeter underfloor boxes System per Area 2 Systems per Floor 2 Systems per Floor  Return Air Path Plenum Plenum  Seasonal Thermostat Set points       Occupied     CoolHeat 74 72 74 72 Unoccupied     CoolHeat 74 72 74 72  Design Temperatures       Cooling Design Temp     IndoorSupply 74 54 74 63 Heating Design Temp     IndoorSupply 72 92 72 85 Air Flows   Minimum Design Flow 0.40 cfm/sqft 0.65 cfm/sqft VAV Minimum Flow 30% 30%  Supply Fans Power & Mtr Eff 2.4 in.WG for offices, 3.5 in. WG for lobbies; High efficiency 2.4 in.WG for offices, 3.5 in. WG for lobbies; High efficiency   HVAC ZONE HEATING, VENT & ECONOMIZERS   Zone Heat Sources & Capacities Fan Type Variable Speed Drive Variable Speed Drive Baseboards None None Heat/ Reheat Electric   30 F 30F DOE-2.1E Command / Keyword BASELINE  BUILDING PROPOSED  BUILDING Input Description  OFFICE SPACE INPUT SOURCE INPUT SOURCE   LIGHTING-W/SQFT 1.1-office, 0.5- corridor, 1.5-elect. Room, 0.9-Restroom, 1.1-Lobby, 0.15-Exterior,1.1-Copy Rm. From: ASHRAE 2004 Table 9.5.1 Pg 64 1.1-office, 0.5- corridor, 1.5-elect. Room, 0.9-Restroom, 1.1-Lobby, 0.15-Exterior,1.1-Copy Rm. From: ASHRAE 2004 Table 9.5.1 Pg 64 W/SQFT ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 20084  UNDERFLOOR SYSTEM IN EQUEST  Equest does not have algorithms to simulate air-flow and hence displaced ventilation systems. So a method suggested in HVAC Simulation Guidelines [3] was adopted which consists of distributing occupant, lighting and equipment power to the thermal zone and an overhead return plenum; this would approximately represent stratification of air and hence cooling load attributed to the thermal zone and return plenum. Table 4 shows a sample zone with the redistribution of power densities. Additionally, to account for latent cooling loads the coil-bypass factor was increased so as to simulate air leaving the coil at 53ºF while the mixed-air leaving the AHU at 65ºF.  Table 5. Distribution of power densities in baseline building and proposed building.  EL1(BASELINE)  Perimeter  Core  Perimeter  Core  Perimeter  Core OPD 137 230 200 193 200 193 LPD 1.11 1.08 1.11 0.99 1.11 0.99 EPD 1.186 1.151 2 1.377 2 1.377  EL1(PROPOSED)    OPD 183 307 267 257 267 257 LPD 0.74 0.72 0.74 0.66 0.74 0.66 EPD 0.79 0.77 1.34 0.92 1.34 0.92 OCCUPANT DENSITY FOR PLENUM:  SPACE AREA O.P.D. O.PD./AREA EL1 West Perim Spc (G.W1) 1575 183 0.1162 2058 EL1 South Perim Spc (G.S2) 4529 183 0.0404 5919 EL1 East Perim Spc (G.E3) 1574 183 0.1162 2058 EL1 North Perim Spc (G.N4) 4380 183 0.0418 5724 EL1 Core Spc (G.C5) 25327 307 0.0121 33100 ∑AREA PER PERSON/AREA OF SPACE   0.3267  AREA OF PLENUM   37385  AREA PER PERSON (PLENUM)   489  LIGHTING POWER DENSITY FOR PLENUM:  EQUIPMENT POWER DENSITY FOR PLENUM: L.P.D. L.P.D.*AREA  E.P.D. E.P.D.*AREA 0.74 1166   0.79 1244 0.74 3352  0.79 3578 0.74 1165  0.79 1244 0.74 3241  0.79 3460 0.72 18235  0.77 19502 Condenser Type  Air Cooled Air Cooled Cooling EER/COP 6.1 COP 9.4 EER – System 1 11.4 EER – System 2 12.3 EER – System 3 Heating Zonal Heating and Reheating Only Zonal Heating  and  Reheating Only ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 20085 ∑AREA L.P.D.*AREA OF SPACE 27159 ∑AREA E.P.D.*AREA OF SPACE  29028 AREA OF PLENUM 37385 AREA OF PLENUM  37385 LIGHTING POWER DENSITY(PLENUM) 0.24 EQUIPMENT POWER DENSITY(PLENUM)  0.26  020000040000060000080000010000001200000140000016000001800000LIGHTS EQUIPMENT HEATING COOLING HEATREJECTIONPUMPS FANS HOT WATEREnergy typesAnnual energy consumption (kWh)LEEDBASELINESYSTEM 1SYSTEM 2SYSTEM 3Figure 2. Comparison of annual energy types for all systems.   The annual cost of electricity for the baseline building at 10cents/kWh, was $584436 as compared to $530808 for System 1 (refer Table 4 for individual system description), $497659 for System 2, and $486211 for System 3. This corresponds to 9.18% for System 1, 14.85% for System 2, and 16.8% for System 3. Evidently, System 2 and System 3 would be able to meet the LEED prerequisite of 14%.    Figure 3. Comparison of annual cost of energy.  ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 20086 System 2 was finally selected for the project and later, in the value engineering phase, the same energy model was used to determine effects of changing glazing and shading devices.   CASE STUDY 2 The five floor community building consisted of children play areas and training rooms on first and second floors; swimming and therapy pools on the third floor; gym, workouts and running track on fourth and fifth floors.   Figure 5. Equest image of community building.  The project goal was to look at all possible energy efficient strategies and estimate payback costs in the SD phase. A LEED-baseline-building energy-model was created per Appendix G, ASHRAE 2004; energy-recovery with heat pipe was implemented per code requirements. A proposed-building energy-model was created with chilled-water system and heat pipe for energy recovery. Table 5 lists the system description of the proposed building. Parametric variations of this were created with the following energy efficient features: 1. Big ceiling fans in all workout areas to reduce total static pressure in ducts by 1in. wg. & increase thermostats by 4°F. This was based on a study (James et al.) which estimates a reduction of 2-6°F in space temperatures with the use of ceiling fans. An external scheduled load was added to the energy model to represent the fan load. 2. Shading on the north-west with vertical fins to block direct sunlight and glare. Shading studies were carried in Ecotect to determine optimum depths and spacing. 3. Daylighting controls using stepped-dimming at perimeter to harvest daylight and save energy (30fc setpoint). 4. Efficient lighting package to include a 20% reduction in lighting power density over ASHRAE 2004 with stepped lighting controls.  5. Five skylights on the fifth floor to harvest daylight. 6. Solar hot water system for therapy pool. 7. Energy Recovery Unit (ERU) with desiccant wheel to treat outside air - Trane Energy Wheel S2500 H, 767,791btu/hr total capacity; Trane CDQ Dessicant Wheel -  137.6lb/hr water vapor transfer, -199,058btu/hr heat transfer capacity.  Enthalpy Wheel type- recovering both sensible and latent heat; Operating mode - both heat/cool; Make up air temperature control- mixed Air Reset; Capacity Control- bypass OA; Operation-OA exhaust DT; OA/Exhaust DT- 5°F. 8. Systems 1-7 combined. This option combines of the above mentioned options from 1 to 7 in a single building.  9. Option 8 with reduction in chiller capacity by 40 ton. This was an approximate reduction in chiller capacity modeled with reduction in loads due to all the above strategies. 10. Option 9 with shading removed. This was done to compare payback time of all other strategies without the most expensive option of external shading device. Option 10 turned out to be the most cost-effective.  11. Option 10 with ceiling fans and efficient lighting removed.       ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 20087 Table 6. HVAC design data for the proposed community building. SYSTEM TYPE 1 (floor 1) SYSTEM TYPE 2 (floor2,4,5) SYSTEM TYPE 3 (floor 3) Temperature 75 F Summer          72 F Winter 75 F Summer  72 F Winter      Pool            82 F Summer        82 F Winter People-schedule A A B Area/person 150 50 300 People-heat gain-latent 200 625 500 People-heat gain-sensible 250 375 340 HVAC SYSTEM DESCRIPTION     Equipment type Chilled water coils with water cooled condensers Cooling Source Chilled water coils Chilled water coils Chilled water coils Heating Source Electric resistance Electric resistance Electric resistance System Type Series powered VAV with elec. Reheat Series powered VAV with elec. Reheat Single Zone Air Handler with Elec. Heat Return Air Path Plenum Plenum Ducted Occupied    Cool 75 72 82 Heat 72 70 82 Unoccupied    Cool 85 85 82 Heat 55 55 82  Design Temperatures    Cooling Design Temp    Indoor 75 75 82 Supply 56 56 60 Heating Design Temp    Indoor 72 72 72 Supply 85 to 95 85 to 95 95 Air Flows  Minimum Design Flow 0.75 cfm/sqft 0.75 cfm/sqft 1 cfm/sqft VAV Minimum Flow 30% primary flow 30% primary flow 100% perimeter 100% core HVAC SYSTEM FANS     Supply Fans    Power & Mtr Eff 3.5 in.WG, High 3.5 in.WG, High 3.5 in.WG, High Fan Type Variable Speed Drive Variable Speed Drive Constant Vol Heat Reheat Electric  30F 30F 30F CHILLED WATER SYSTEM  Pump Configuration Single system pumps, variable primary flow Number of System Pumps 1 CHW Loop Flow  Constant speed Pump Control VFD/VSD ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 20088 Loop Pump Motor Efficiency Premium (93% ) Chiller Type Electric Centrifugal Hermetic Condenser Type Water Cooled Compressor Type  Constant Speed Number & size 2, 200-400 TONS Chiller Efficiency 0.50 kW/ton WATER COOLED CONDENSOR / COOLING TOWER  Condenser Configuration Open Tower Temperature Control Fixed Setpoint 86F Capacity Control variable speed fans Chilled Water Setpoint Type OA Reset CHW Min Temp 42F CHW Max Temp 58F Operation Stand-by   One shortcoming of the simulations was the inability to model thermal mass of pool-water. Another approximation lies in the inability of Equest to integrate a separate outside-ahu with each floor-ahu in Equest. To overcome this, dummy zones were created with ‘0’ loads; OAHUs were assigned to these with energy-recovery capacities per design. Each floor-ahu was then assigned to draw outside-air from these.  Figure 5 compares the annual cost savings due to the individual energy efficient strategies, the respective investment, payback time, cumulative income in twenty-five years and the LEED points earned by each option.            It could be seen that the proposed building was able to meet the LEED 2.2 pre-requisite of 14% with the chilled water system. Among individual strategies, skylights give the fastest payback followed by energy-recovery unit with vapor wheel. Efficient lighting, ceiling fans and perimeter daylight controls follow next. The external shading devices considered for this project remain  unprofitable due to cost and orientation of the building. Combination of all the strategies without the shading device could achieve a payback of 3.1 years. ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 20089   Figure 5. Cost savings for different energy saving strategies.   CONCLUSIONS Energy modeling done in the early design phase helps in making significant decisions during the design process like effects of changing glazing, shading devices, operation schedules and lighting/equipment efficiencies. It also helps in making decisions on HVAC systems and testing atypical technologies which need integration in buildings at the SD phase like energy recovery, skylights and daylighting controls.  Simulations at this stage come with assumptions with regards to details of systems and sometimes architectural   design, but are nevertheless useful. REFERENCES ASHRAE 2004. ANSI/ASHRAE/IESNA Standard 90.1-2004. Energy Standard for Buildings Except Low-rise Residential Building. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. Biesterveld M., Harshaw J., Murphy J., 2008. Energy-saving strategies for LEED Energy and Atmosphere Credit 1. Trane Engineers newsletter, volume 37-2, 2008.  ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 200810 Browning, B. K., 2002. Direct Expansion Air Conditioning System Selection for Hot & Humid  Climates. Proceedings of Thirteenth Symposium on Improving Building Systems in Hot and Humid Climates. James. P., J. Sonne. R. Vieira, D. Parker, and M. Anello. 1996. "Are Energy Savings Due to Ceiling Fans Just Hot Air?'Proceedinas of the ACEEE Summer Studv on Enerw Efficiency in Buildings, 8:89-93. American Council for an Energy-Efficient Economy, Washington D.C.  ACKNOWLEDGEMENT The authors would like to thank Brian Malarkey, Kirksey for his initiative that made research into these two projects possible; and Jonthan Curtin, Wylie Associates, for technical help.  ESL-HH-08-12-38Proceedings of the Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, Plano, TX, December 15-17, 2008

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Case Studies of Systems Integration through Energy Simulation During Early Design Phase

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Case Studies of Systems Integration through Energy Simulation During Early Design Phase

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Texas A&M University

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