NATL INST OF STAND & TECH

A11107 31021=0

NBSIR 83-2746

Strategies for Energy Conservation

for A Large Office Building

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Equipment Division

Washington, DC 20234

July 1983

Prepared for ~ cfice of Building Energy Research and Development

UL fice Qf Conservation and Renewable Energy

100 S. Department of Energy

,[J55 ashington, DC

33-2746

1933

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NBSIR 83-2746

* t • STRATEGIES FOR ENERGY CONSERVATION

FOR A LARGE OFFICE BUILDING

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James V. Kao

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Equipment Division

Washington, DC 20234

July 1983

Prepared for Office of Building Energy Research and Development

Office of Conservation and Renewable Energy

U.S. Department of Energy

Washington, DC

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director
* ’ -

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ABSTRACT

A comparative analysis is made of the thermal performance of selected HVAC

systems and control strategies commonly employed in large office buildings. The

comparisons are made for six geographical locations representing wide climatic

variations within the continental United States.

Hour-by-hour simulations with the BLAST computer program are used to obtain the

yearly heating, cooling, and fan energy consumption of a twelve-story large

office building. The HVAC systems simulated are constant volume reheat, variable air volume, dual-duct, and fan-coil systems. The control strategies

tested are dry-bulb temperature economy cycles, enthalpy economy cycle, supplyair-temperature resetting, and the combinations of these strategies. The

results of these simulations are presented and discussed. Substantial energy

consumption differences are shown to exist.

Key words: building control strategies; building energy conservation; building

thermal performance; HVAC systems

iii
PREFACE

This report is one of a series documenting NBS research and analysis efforts in

developing energy and cost data to support the Department of Energy/National

Bureau of Standards Building Energy Conservation Criteria Program. The work

reported in this document was performed under the Energy Analysis of Control

Strategies project, a part of the controls program element managed by Building

Systems Division, Office of Building Energy Research and Development, U.S.

Department of Energy. The NBS effort was supported by DoE/NBS Task Order A008-

BCS under Interagency Agreement No. EA77A 01-6010.
CONTENTS

Page

Abstract iii

Preface iv

List of Tables vi

List of Figures vii

1. Introduction 1 2 . Energy Simulation 2 2.1 Building Model 2 2.2 HVAC System Simulation and Control Strategies 2 3 . Results and Discussion 8

3.1 Energy Consumption Results 8

3.2 Comparison of Strategies 9

4. Summary and Conclusions 13

References 17

v

»•
LIST OF TABLES

Page

Table 1. Annual Energy Consumption - Lake Charles, LA 18

Table 2. Annual Energy Consumption - Madison, WI 19

Table 3. Annual Energy Consumption - Nashville, TN 20

Table 4. Annual Energy Consumption - Santa Maria, CA 21

Table 5. Annual Energy Consumption - Seattle, WA 22

Table 6. Annual Energy Consumption - Washington, DC 23

Table 7. Comparative Annual Energy Consumption - Lake Charles, LA . . . 24

Table 8. Comparative Annual Energy Consumption - Madison, WI 25

Table 9. Comparative Annual Energy Consumption - Santa Maria, CA . . .

.

2b

Table 10. Comparative Annual Energy Consumption - Nashville, TN 27

Table 11. Comparative Annual Energy Consumption - Seattle, WA 28

Table 12. Comparative Annual Energy Consumption - Washington, DC 29
LIST OF FIGURES

Page

Figure 1. Large office building model 30

Figure 2. Internal load profiles 31

Figure 3. Cooling energy consumption of case 1 — base reheat 32

Figure 4. Cooling energy consumption of case 2 —- base reheat with

temperature economy cycle 32

Figure 5. Cooling energy consumption of case 3 — base reheat with

return air economy cycle 33

Figure 6. Cooling energy consumption of case 4 — base reheat with

enthalpy economy cycle 33

Figure 7. Cooling energy consumption of case 5 — base reheat with

supply air reset by outside air 34

Figure 8. Cooling energy consumption of case 6 — base reheat with

supply air reset by zone load demand 34

Figure 9. Cooling energy consumption of case 7 — base reheat with

enthalpy economy cycle and supply air reset by zone load

demand 33

Figure 10. Cooling energy consumption of case 8 — base VAV with

enthalpy economy cycle 35

Figure 11. Cooling energy consumption of case 9 — base VAV with

enthalpy economy cycle 36

Figure 12. Cooling energy consumption of case 10 — base RH for

interior zones , base DD for perimeter zones 36

Figure 13. Cooling energy consumption of case 11 — base VAV for

interior zones , base DD for perimeter zones 37

Figure 14. Cooling energy consumption of case 12 — base RH with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle for perimeter zones 37

Figure 15. Cooling energy consumption of case 13 — base VAV with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle for perimeter zones 38

vii
LIST OF FIGURES - (Continued)

Page

Figure 16. Cooling energy consumption of case 14 — base RH with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot deck reset by outside air

for perimeter zones 38

Figure 17. Cooling energy consumption of case 15 — base VAV with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot deck reset by outside air

for perimeter zones 39

Figure 18. Cooling energy consumption of case 16 — base RH with

enthalpy economy cycle and supply air reset by zone demand

for interior zones, base DD with enthalpy economy cycle and

hot-cold decks reset by zone demands for perimeter

zones 39

Figure 19. Cooling energy consumption of case 17 — base VAV with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot-cold decks reset by zone demands for perimeter zones 40

Figure 20. Cooling energy consumption of case 18 — base RH with

enthalpy economy cycle and supply air reset by zone demand

for interior zones, base VAV with enthalpy economy cycle

for perimeter zones 40

Figure 21. Cooling energy consumption of case 19 — base RH with

enthalpy economy cycle and supply air reset by zone demand

for interior zones, fan-coil for perimeter zones 41

Figure 22. Cooling energy consumption of case 20 — base VAV with

enthalpy economy cycle for interior zones, fan-coil for

perimeter zones 41

Figure 23. Cooling energy consumption of cases 1 through 7 — all RH cases 42

Figure 24. Cooling energy consumption of cases 8 and 9 — all VAV cases 43

Figure 25. Cooling energy consumption of cases 11, 13, 15, and 17 —

VAV for interior zones, DD for perimeter zones 44

Figure 26. Cooling energy consumption of cases 7, 9, 17, and 20 —

selected case comparisons 45

Figure 27. Heating energy consumption of case 1 — base reheat 46

viii
LIST OF FIGURES - (Continued)

Page

Figure 28. Heating energy consumption of case 2 — base reheat with

temperature economy cycle 46

Figure 29. Heating energy consumption of case 3 — base reheat with

return air economy cycle 47

Figure 30. Heating energy consumption of case 4 — base reheat with

enthalpy economy cycle 47

Figure 31. Heating energy consumption of case 5 — base reheat with

supply air reset by outside air 48

Figure 32. Heating energy consumption of case 6 — base reheat with

supply air reset by zone load demand 48

Figure 33. Heating energy consumption of case 7 — base reheat with

enthalpy economy cycle and supply air reset by zone load

demand 49

Figure 34. Heating energy consumption of case 8 — base VAV with

enthalpy economy cycle 49

Figure 35. Heating energy consumption of case 9 — base VAV with

enthalpy economy cycle 50

Figure 36. Heating energy consumption of case 10 — base RH for

interior zones, base DD for perimeter zones 50

Figure 37. Heating energy consumption of case 11 — base VAV for

interior zones, base DD for perimeter zones 51

Figure 38. Heating energy consumption of case 12 — base RH with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle for perimeter zones 51

Figure 39. Heating energy consumption of case 13 — base VAV with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle for perimeter zones 52

Figure 40. Heating energy consumption of case 14 — base RH with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot deck reset by outside air

for perimeter zones 52

ix
LIST OF FIGURES - (Continued)

Page

Figure 41. Heating energy consumption of case 15 — base VAV with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot deck reset by outside air

for perimeter zones 53

Figure 42. Heating energy consumption of case 16 — base RH with

enthalpy economy cycle and supply air reset by zone demand

for interior zones, base DD with enthalpy economy cycle and

hot-cold decks reset by zone demands for perimeter

zones 53

Figure 43. Heating energy consumption of case 17 — base VAV with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot-cold decks reset by zone demands for perimeter zones 54

Figure 44. Heating energy consumption of case 18 — base RH with

enthalpy economy cycle and supply air reset by zone demand

for interior zones, base VAV with enthalpy economy cycle

for perimeter zones 54

Figure 45. Heating energy consumption of case 19 — base RH with

enthalpy economy cycle and supply air reset by zone demand

for interior zones, fan-coil for perimeter zones 55

Figure 46. Heating energy consumption of case 20 — base VAV with

enthalpy economy cycle for interior zones, fan-coil for

perimeter zones 55

Figure 47. Heating energy consumption of cases 1 through 7 — all RH cases 56

Figure 48. Heating energy consumption of cases 8 and 9 — all VAV

cases 57

Figure 49. Heating energy consumption of cases 11, 13, 15, and 17 —

VAV for interior zones, DD for perimeter zones 58

Figure 50. Heating energy consumption of cases 7, 9, 17, and 20 —

selected case comparisons 59

x
1 . INTRODUCTION

This report is the third in a series of reports by researchers at the National

Bureau of Standards which compare the energy consumption of alternative heating, ventilating, and air conditioning (HVAC) systems and control strategies

for commercial buildings. The purpose of this report, along with the two

previous reports which studied a small office building [1]* and a large retail

store [2J, was to generate comparative energy use data for various building

types in different geographical locations in the United States. These studies

were intended to derive general guidelines limited to HVAC control strategy

selections for building operators and designers. The present study which

specifically deals with large office buildings uses a large multi-story building as a model. The energy saving potential for large office buildings as a group is substantial, since over 15 percent of the buildings larger than 50,000

ft2 (4,645 m2

) in floor area are office buildings [3]. The HVAC systems

and control strategies employed in this study were those most commonly used

for this type of building. The results and conclusions of this study should

aid prospective users in making preliminary decisions about strategies for

air-handling system control in both new and renovative work.

The energy program used in this study was the Building Loads Analysis and

System Thermodynamics Program (BLAST, Version 2.0) [4]. The cities used for

the energy simulations in the present series of reports [including 1, and 2]

were Lake Charles, Louisiana; Madison, Wisconsin; Nashville, Tennessee; Santa

Maria, California; Seattle, Washington; and Washington, D.C. These cities

range from approximately 1500 to 8000 heating degree days (65°F base) and from

100 to 3000 cooling degree days (65°F base), and represent a wide variety of

climatic conditions in the United States.

The energy consumption results of this study were limited to the energy

consumed by the air-handling systems. For the readers who are interested in

comparing the dollar cost of different systems and control strategies, it is

necesary to modify the present data with energy transmission losses, plant

efficiencies, and energy costs.

Since the BLAST-2 program is an hourly energy program, the energy effect caused

by the dynamics of the control component interactions may not be included in

the energy consumption results. The size of this effect, which may be

significant, was not investigated in this study.

* See references at end of text.

1
2. ENERGY SIMULATION

2.1 BUILDING MODEL AND WEATHER DATA

The building being modeled was a twelve-story general office building, 200

feet (61.0 m) long in the east-west direction and 100 feet (30.5 m) wide in

the north-south direction. The building dimensions and pertinent construction

data, as well as the thermal zone arrangements, are shown in figure 1. The

building was of light construction and was well insulated. The f loor-to-f loor

height was 13 feet (4.0 m). The fenestration area was approximately 42 percent

of the gross wall area on all four sides of the building. The daily occupancy,

lighting, and equipment profiles and loadings are shown in figure 2. It was assumed that 30 percent of the lighting load was absorbed by the return air

directly, without imposing a cooling load on the space. During the system

operational hours, the building was assumed to be pressurized and have no infiltration. During system off hours, when no outside air was admitted into

the air-handling systems, the infiltration was assumed to be approximately 0.2

air changes per hour in the perimeter zones. This infiltration rate agreed

closely with the measured infiltration rates of a large commercial building of

similar exterior wall construction [5]. The systems admitted ventilation air

at 10 percent of the supply air. This ventilation rate equaled no less than

8 cfm (3.78 x 10“^ m^/s) per person.

The building was zoned by interior/exterior spaces and exposures. Therefore,

every floor had four exterior thermal zones and one interior thermal zone. Each exterior zone which was modeled had a floor area of 20 ft x 20 ft

(6.1 m x 6.1 m) while each interior zone had a floor area of 2000 ft^

(185.8 m^). The modeled zone data were multiplied by the appropriate numbers

to obtain the total air-handling system energy consumption.

The interior area of a typical floor space was about 43 percent of the total

net floor area of that space. In order to reduce the computation cost, only

the four exterior zones of a typical floor space and the interior zones of the

top floor and typical floor were simulated. Therefore, six zone simulations

were performed for each system/ control strategy pair instead of the actual

fifteen zone simulations (bottom, typical, and top floors) possible. The error introduced by this simplification, in terms of total supply air quantities,

was calculated to be about 0.6 percent for Santa Maria and well below 0.5

percent for the other five cities. The average supply air quantities ranged

between 0.84 cfm per ft^ (3.96 x 10"^ m^/s per m^) of net floor area for

Santa Maria to 1.04 cfm per ft^ (4.91 x 10“^ m^/s per m^) of net floor area for Nashville.

The weather data used for the simulations were from the Typical Meteorological

Year (TMY) climatic tapes [6].

2.2 HVAC SYSTEM SIMULATION AND CONTROL STRATEGIES

Four basic types of HVAC systems commonly used for high-rise office buildings were simulated in this study. They were constant volume terminal reheat,

variable air volume, dual-duct, and fan-coil systems. All four systems were

2
modeled for the perimeter zones while only the terminal reheat and variable air

volume systems were used for the interior zones. A dual-duct system was not

modeled for the interior system because of the relatively smaller load variations typical of the interior zones. The perimeter and interior zones were

simulated separately. The energy consumptions of the four different perimeter

systems were combined with those of the two interior zones to give the total

building consumptions of different perimeter-interior combinations.

The capacities of the different air-handling systems were sized to keep the

space temperatures between 68°F (20.0°C) and 78°F (25.6°C) during office hours.

ASHRAE [7] 97.5 percent design dry-bulb temperature and 2.5 percent design

dry-bulb/mean coincident wet-bulb temperature were used in zone load calculations. However, the yearly simulation runs indicated that the 78°F (25.6°C)

upper space temperature was exceeded by more than 1°F (0.6°C) during high load

hours for some cities. The night and weekend heating setback temperature was 52°F (11.1°C) . The air handling system fans ran continously during office

hours, from 8 a.m. to 8 p.m, and ran intermittently during setback hours. It was assumed that chilled water was available year-round during office hours

and that the throttling range^ of the cooling coil controller was 3°F (1.7°C).

The control strategies tested in this study included the use of various outside

air economy cycles, the resetting of cold and hot duct temperatures by outside

air temperature or by zone load demands, and combinations of these strategies.

Details of these strategies are given in the following paragraphs.

A. Case 1 — Base Reheat (RH) Systems for Whole Building

Constant volume terminal reheat systems were simulated for both perimeter

and interior zones. The supply-air temperature was 59 °F (15.0°C) which

included the fan heat gain. Ventilation air equivalent to 10 percent of

supply air was introduced to the systems during all office hours. This

amount of outside air is defined as the minimum outside air in this paper.

The supply air fan and return air fan pressures were assumed to be 3 in. of

water (7.5 x 10^ Pa) and 0.5 in. of water (1.2 x 10^ Pa), respectively.

B. Case 2 — Reheat (RH) Systems with Temperature Economy Cycle

A temperature economy cycle was added to case 1. The mixed-air temperature

of the return and outside-air streams was maintained by modulating the

dampers to satisfy the supply-air sensor setting. When the outside-air

temperatures rose above the setting of this sensor, the outside-air damper

was closed to its minimum outside air position and the building cooling was accomplished entirely by the chilled water.

1 Throttling range can be defined as the change required, in a proportional

control system, in a controlled variable (such as air temperature) to

move the controlled device (such as a coil valve) from one of its extreme

limits of travel to the other (such as from fully open to fully closed).

3
C. Case 3 — Reheat ( RH) Systems with Return Air Economy Cycle

This strategy was similar to that of case 2 except that the return-air

temperature sensor was compared with the outside-air temperature. Whenever

the outside-air temperature was below the return-air temperature, 100

percent outside air was admitted to offset part of the building cooling

load. When the outside temperature was below the supply-air temperature

setting, the amount of outside air and return air was mixed to satisfy the

supply-air setting.

D. Case 4 — Reheat (RH) Systems with Enthalpy Economy Cycle

When the enthalpy of the outside air was lower than that of the return

air, the full amount of outside air was admitted to the systems, providing

the temperature of the mixed air was not below the temperature setting of

the supply air. Otherwise, only the minimum amount of outside air was admitted. This was accomplished by having enthalpy sensors in the return

and outside air streams.

E

.

Case 5 — Reheat (RH) Systems with Supply-Air Temperature Reset by Outside

Air Temperature

The supply-air temperature of the perimeter system was changed from 59°

F

(15.0°C) to 63°F (17.2°C) inversely with the outside air temperature, following a straight line relationship, from 90°F (32.2°C) to 70°F (21.1°C).

Although this reset schedule was used for all 6 cities to demonstrate the

benefit of resetting the supply air, it should not be construed as a recom- mended schedule. Except for the perimeter system resetting, this case is

the same as case 1.

F

.

Case 6 — Reheat (RH) System with Supply Air Temperature Reset by Zone Load

Demand

Instead of using an outside-air-temperature sensor to control the supply-air

temperature, as described in case 5, multiple zone temperature sensors were

simulated. These reset the supply air temperature to satisfy the peak

demand zone during system operating hours. No supply-air temperature limit was specified in the input data. This strategy was applied to both perimeter

and interior systems.

G. Case 7 — Reheat (RH) System with Combined Strategies

This case combined the best economy cycle strategy with the best supply-air

resetting strategy described above. In other words, both the enthalpy

economy cycle and resetting supply-air temperature by zone load demand were applied to the entire building.

H. Case 8 — Base Variable Air Volume (VAV) System

Variable air volume systems were used for both perimeter and interior zones. The minimum supply-air quantities of the VAV thermal units were set at 20

4
percent of the supply air. The air-handling systems admitted the minimum

outside air percentage at all times. Since the building had large interior

spaces and the internal load variations were relatively small, the toilet

exhaust and building pressurization could be maintained even at low load

periods. The supply-air fan pressure was changed from 3 in. of water

(7.5 x 10 2 Pa) to 3.5 in. of water (8.7 x 10 2 Pa) in the simulation to

account for the added terminal unit pressure requirement. The supply-air

temperature setting was 59°F (15.0°C), the same as for the reheat systems.

The perimeter system had reheat coils in the terminal units, while the

interior system had only the air volume controls.

I. Case 9 — Variable Air Volume (VAV) System with Enthalpy Economy Cycle

An enthalpy economy cycle was added to the VAV system from case 8.

J. Case 10 — Base Reheat (RH) System for Interior Zones and Base Dual-Duct

(DP) System for Perimeter Zones

A dual-duct system was used for the perimeter zones for this case and the

following 7 cases (cases 10 through 17). The dual-duct system had preheat coils in the mixed-air stream with the main heating and cooling coils

located in the hot and cold ducts. Case 10 combined the dual-duct system

with a reheat system for the interior zones. Both systems used the

minimum outside air percentage at all times and there was no resetting of

any temperature controller. The cold air temperature was set at 59°F

(15.0°C) and the hot air temperature was set at 140°F (60.0°C) year-round.

The supply and return fan air flow rates were the same as those of the

reheat systems. The supply-air fan pressure was also 3.5 in. of water

(8.7 x 102 Pa) as in the VAV cases because of the pressure requirement

of the mixing boxes. The cooling and heating coil capacities were not

changed from those of the reheat systems. The energy losses from mixing

damper leakage were not considered in any cases.

K. Case 11 — Base Variable Air Volume (VAV) System for Interior Zones and

Base Dual-Duct (DP) System for Perimeter Zones

In this case, the interior system was the same as the interior system of case 8 and the perimeter system was the same as in case 10. Again, only

minimum outside air was used during office hours.

L. Case 12 — Reheat (RH) System for Interior Zones and Dual-Duct (DP) System

for Perimeter Zones, Enthalpy Economy Cycle

In this case, an enthalpy economy cycle was added to case 10.

M. Case 13 — Variable Air Volume (VAV) System for Interior Zones and DualDuct (DP) System for Perimeter Zones, Enthalpy Economy Cycle

In this case, an enthalpy economy cycle was added to case 11.

5
N. Case 14 — Reheat ( RH) System for Interior Zones and Dual-Duct (DP) System

for Perimeter Zones, Enthalpy Economy Cycle, Resetting Hot Deck Temperature

by Outside Air Temperature for Dual-Duct System

This case is the same as case 12 except that the hot-air duct temperature

of the dual-duct system was reset inversely according to the outside air

temperature. The hot air temperature was 140°F (60.0°C) when the outside

air was 0°F or below (-17.8°C). The hot air temperature was 70°F (21.1°C)

when the outside was also 70°F (21.1°C) or above.

0.

Case 15 — Variable Air Volume (VAV) System for Interior Zones and DualDuct (DP) System for Perimeter Zones, Enthalpy Economy Cycle, Resetting

Hot Deck Temperature by Outside Air Temperature for Dual-buct System

In this case, the resetting of hot air temperature was applied to the dualduct system of case 13. The reset schedule was the same as that of case 14.

P. Case 16 — Reheat (RH) System for Interior Zones and Dual-Duct (DP) System

for Perimeter Zones, Enthalpy Economy Cycle, Resetting Both Hot and Cold

Decks

This case is similar to case 14 except that both the hot and cold air

temperatures were reset by sensors in the highest heating and cooling

demand zones, respectively. In doing so, the dual-duct mixing loss was minimized. The reset temperature was also set between specific limits.

Hot air temperature was limited to between 70°F (21.1°C) and 140°F (60.0°C).

The cold air temperature was confined to between 59°F (15.0°C) and 63°F

(17.2°C).

Q.

Case 17 — Variable Air Volume (VAV) System for Interior Zones and DualDuct (DP) System for Perimeter Zones, Enthalpy Economy Cycle, Resetting

Both Hot and Cold Decks

This case is similar to case 16 except that the interior system was replaced by a VAV system as described in case 9.

R. Case 18 — Reheat (RH) System for Interior System and Variable Air Volume

(VAV) System for Perimeter System, Enthalpy Economy

This case is a mixture of cases 7 and 9. The interior reheat system of case 7 is combined with the perimeter VAV system of case 9.

S. Case 19 — Reheat (RH) System for Interior Zones and Fan-Coil (FC) System

for Perimeter Zones

The perimeter was simulated with four-pipe room fan-coil units. Because

of the limitations of BLAST-2 program, only fan-coil units with direct

outdoor air connections were modeled. The fan-coil unit fan pressure was assumed to be 0.8 in. of water (2.0 x 10^ Pa). Chilled water was turned

off during nonoffice hours, although both hot water and chilled water were assumed to be available year-round. The BLAST default value of 45°F (7.2°C)

6
for the entering chilled water temperature was used. The energy consumption

for transporting the hot and chilled water to the fan-coil units was not

included in the simulations. The interior system used the same reheat system as that of case 7 which had an enthalpy economy cycle and reset the

supply air temperature by zone demand.

T. Case 20 — Variable Air Volume (VAV) System for Interior Zones and Fan-Coil

(FC) System for Perimeter Zones

In this case, the reheat system of case 19 was replaced by the VAV system

of case 9, which used an enthalpy economy cycle. The perimeter fan-coil

units were as described in case 19.

7
3. RESULTS AND DISCUSSION

3.1 ENERGY CONSUMPTION RESULTS*

The yearly energy consumption for heating, cooling, and fan operation resulting

from different strategies and combinations of strategies is listed for each of

the six cities in tables 1 through 6. Table 7 through 12 give the yearly

heating, cooling, and fan energy consumption per unit floor area based on the

total gross floor area of the building, for each of the six cities. These six

tables also give the comparative energy consumption normalized to the consumption of the base reheat case (case 1). As described in section 2.3, cases 2 through 6 were single strategy cases, where only one control strategy was applied to the base reheat case so that the relative savings of the basic

strategies may be judged. Case 7 is a combined strategy case — using both

the economy cycle and reset strategy for the reheat system. Variable air

volume systems were compared in cases 8 and 9. In cases 1 to 9, the entire

building used the same type of system and control strategies. Cases 10 through

17 combined reheat or variable air volume systems for the interior zones with

dual-duct systems for the perimeter zones. Case 18 combined reheat interior

zones with variable air volume perimeter zones. Cases 19 and 20 used perimeter

fan-coil units with reheat and variable air volume in the interior zones,

respectively.

The cooling and heating energy consumption results were also plotted against

the cooling degree days and heating degree days. The reason for using degree

days to correlate energy consumptions was given in reference 2. It may be

worthwhile to repeat it here:

"It is always desirable, from the application point of view, to

have some parameters to correlate with the energy consumption data of one building so that the data may be applied to similar buildings of

different climatic conditions. The authors of this paper realize the

difficulty of finding these parameters to apply to commercial buildings. However, a parameter, even a crude one, may give HVAC designers

assistance in deciding system and control strategies during the early course of the building design and provide budget figures for comparisons. This is not to say that the correlated data should be used

indiscriminately. Detailed energy calculations with an appropriate

method must be performed for a building in order to have accurate

energy consumption values. Evidently one of the most influential

parameters affecting a building energy consumption is the outdoor

ambient dry-bulb temperature. The dry-bulb temperature changes

the building energy consumption through ventilation air and building

structure thermal conductance directly, and through ambient humidity

indirectly. Some measures of the dry-bulb temperature for a climatic

location are daily average temperature, monthly average temperature,

degree-hour data, frequency data (BINs), etc. However, the most

* Energy consumption results are presented in English units only, for clarity.

8
available data for most of the cities in the United States are the

heating and cooling degree days." [2, page 7]

Figures 3 through 22 show the cooling energy consumption of the 20 strategies

using 65°F (18.3°C) based cooling degree days as the independent variable.

Figure 23 compares the cooling energy consumption of the single control

strategy cases as well as the combined strategy case in which the entire building is served by reheat systems. Figure 24 compares the two variable air volume

strategies — one with minimum outside air only and one with enthalpy economy

cycles. Figure 25 shows the cooling energy consumption where the interior

system was of the variable air volume type and the perimeter zones were served

by dual-duct system. Finally, figure 26 displays the better energy saving

system/ control strategy combinations. Figures 27 through 50 plot the corresponding heating energy consumption data for the six cities as a function of

heating degree days using 65°F (18.3°C)as the base.

3.2 COMPARISON OF STRATEGIES

A. Outside Air Economy Cycles

Three different outside air economy cycles were applied to the reheat

systems of the entire building. They were the temperature economy cycle

which tried to maintain the mixed air temperature at that of the cold

supply air temperature; the return air economy cycle which compared the

return air temperature with the outside air temperature and admitted 100

percent outside air when the outside air temperature was lower than the

return air temperature; and the enthalpy economy cycle which was similar

to the return air economy cycle except that enthalpies were used for

comparisons instead of temperatures.

In terms of cooling energy savings, generally the enthalpy economy cycle

saved the most energy and the temperature economy cycle saved the least.

A few exceptions can be noted. The temperature economy cycle did slightly

better than the return air economy cycle for Lake Charles, and the return

air economy cycle edged the enthalpy economy cycle in Santa Maria and

Seattle. However, the differences in all three cases were within two

percent of each other. The following table compares the economy cycle

lists the annual energy consumption ratios of various cases for the six

cities.

9
Lake

Charles Madison Nashville

Santa

Maria Seattle

Washington

,

DC

Temperature Economy (Case 2 vs Case 1) (RH)

Cooling 0.90 0.61 0.77 0.76 0.49 0.68

Heating 1.09 1.18 1.15 1.25 1.24 1.16

Return Air Economy (Case 3 vs Case 1) (RH)

Cooling 0.91 0.52 0.70 0.42 0.28 0.61

Heating 1.25 1.25 1.27 1.51 1.35 1.26

Enthalpy Economy (Case 4 vs Case 1) (RH)

Cooling 0.83 0.50 0.66 0.43 0.28 0.58

Heating 1.19 1.24 1.24 1.51 1.35 1.24

Enthalpy Economy (Case 9 vs Case 8) (VAV)

Cooling 0.85 0.66 0.79 0.55 0.41 0.73

Heating 1.07 1.00 1.01 1.20 1.01 1.01

Enthalpy Economy (Case 13 vs Case 11) (Interior VAV, Perimeter DD)

Cooling 0.84 0.51 0.68 0.48 0.29 0.59

Heating 1.08 1.18 1.14 2.00 1.37 1.16

All comparisons in the above table are for single strategy cases. When

other strategies were added to the economy cycles, the energy changes were

not necessarily the same as indicated here. In all economy cycle cases,

the cooling savings were partly offset by increases in heating energy

increases. The reason for the increased heating energy was the decreased

supply-air temperature. When the economy cycle was used, the cooling coil

load decreased and the cooling-coil controller maintained a lower air temperature than the temperature would otherwise be, due to the controller

throttling range effect. The economy cycle was usually in effect when the

building was at part cooling load conditions so that the supply-air temperature to the spaces needed to be adjusted upward for most systems. The

economy cycle cases, which are compared in the above table, all had fixed

supply air temperature and flow rates, except for the VAV systems. Therefore, all the reheat and dual-duct systems needed either more reheating or more hot air mixing to compensate for the excessive cooling capacity,

although the effect of this waste was dependent on the particular system.

The self-adjusting nature of the VAV systems (case 9 vs case 8) avoided

this waste by reducing the cooling capacities delivered to the spaces.

The higher heating increases (although quite small) which were seen in

Santa Maria probably could be reduced by using smaller minimum supply air

ratios than the 20 percent used in the simulations.

10
B. Supply Air Temperature Reset

For the single-strategy reheat systems, the supply air temperature was reset by sensing the outside air temperature (case 5, see paragraph 2.3.E)

or by sensing the maximum cooling load demand zones (case 6, see paragraph

2.3.F). For the combined strategy reheat system, the enthalpy economy

cycle was combined with the resetting of supply air by the latter strategy

(case 7, see paragraph 2.3.G). The energy consumption of these three cases as compared to the base reheat case (case 1) is listed in tables 7 through 12 and is repeated below.

Lake Santa Washington

,

Charles Madison Nashville Maria Seattle DC

Reset by Outside Air Temperature (Case 5 vs Case 1) (RH)

Cooling 0.89 0.82 0.86 0.84 0.81 0.84

Heating 0.78 0.88 0.84 0.72 0.87 0.87

Reset by Maximum Cooling Load Demand Zones (Case 6 vs Case 1) (RH)

Cooling 0.75 0.64 0.70 0.76 0.62 0.67

Heating 0.43 0.61 0.47 0.53 0.47 0.51

Enthalpy Economy and Reset by Maximum Cooling Load Demand Zones

(Case 7 vs Case 1) (RH)

Cooling 0.63 0.36 0.48 0.83 0.19 0.43

Heating 0.57 0.85 0.69 0.88 0.81 0.76

As stated previously, the supply air temperature of the outside air reset case was set at 59°F (15.0°C) when the outside air was 90°F (32.2°C), and at

63°F (17.2°C) when the outside air was 70°F (21.1°C). This reset schedule

provided a good match between the system cooling capacity with the zone loads,

yet it limited the space humidity to reasonable levels during off-peak hours.

Case 5 did not reset the supply air for the interior zones. This resulted

in lesser savings for case 5 than for cases 6. For the same reason, a direct

comparison of cases 5 and 6, using the energy consumption numbers, is not

appropriate. Both the heating and cooling energy savings of case 6 over case 1 were substantial. The addition of enthalpy economy cycles to the

resetting strategy reduced the cooling energy demand. In the meantime, the

heating energy requirement was drastically reduced from that of the enthalpy

strategy alone (comparisons may be found in tables 7 through 12 or in the

table under paragraph 3. 2. A).

Resetting the dual-duct system temperature was simulated by either resetting

the hot air temperature alone or by resetting both hot and cold air. The

former strategy was popularly used even before energy savings became fashionable and was usually done by using the outside air temperature as the resetting parameter. The latter case is relatively new and may use control signals

11
from the thermal zones to reset the air temperatures. A comparison of

heating and cooling energy consumption for various dual-duct cases when

combined with reheat interior system is shown in the following table.

All cases used enthalpy economy cycles.

Lake

Charles Madison Nashville

Santa

Maria

Washington,

Seattle DC

Hot Air Reset by O.A. (Case 14 vs Case 12) (Interior RH, Perimeter DD)

Cooling .73 0.68 0.72 .77 .71 .70

Heating .48 0.83 0.68 .69 .84 .75

Hot and Cold

(Interior RH,

Air Reset by Zone

Perimeter DD)

Demands (Case 16 vs Case 12)

Cooling 0.71 0.63 0.67 .66 .59 .66

Heating .42 0.74 0.58 .59 .70 .65

Reset Hot Air by O.A.

(Case 16 vs Case 14) vs Reset

( Interior

Hot and Cold Air by

RH, Perimeterior DD)

Zone Demands

Cooling 0.96 0.93 .94 .85 .82 .94

Heating 0.87 0.88 .86 .85 .83 .86

The same interior

cycles

.

dual-duct strategies

systems are compared

which were combined with variable air volume

below. Again, all cases had enthalpy economy

Lake Santa Washington,

Charles Madison Nashville Maria Seattle DC

Hot Air Reset by O.A. (Case 15 vs Case 13) (Interior VAV, Perimeter DD)

Cooling .76 .70 .74 .79 .73 .72

Heating .47 .84 .69 .75 .88 .76

Hot and Cold Air Reset by Zone Demands (Case 17 vs Case 13)

(interior VAV, perimeter DD)

Cooling .73 .64 .69 .67 .59 .68

Heating .38 .71 .56 .60 .69 .62

Reset Hot Air by O.A. vs Reset Hot and Cold Air by Zone Demands

(Case 17 vs Case 15) ( Interior VAV, Perimeter DD)

Cooling .96 .92 .93 .85 .82 .94

Heating .82 .85 .81 .79 .78 .81

Both of the above tables indicate that the zone controlled reset of both

hot and cold air saved more than the hot air reset controlled by the outside air temperature. The ratio of energy savings in these two tables are quite close, which reflects the rather constant interior load nature of

12
the building, and perhaps a general characteristic of office interior

zones

.

C. Fan-Coil Systems

Cases 19 and 20 had four-pipe fan-coil systems for the perimeter zones,

with the hot and cold water available year-round. A fixed amount of

outside air was introduced directly to the fan-coil units during operating

hours. In the following table, the heating and cooling energies are com- pared for the three combinations in the perimeter zone — variable air

volume, dual-duct, and fan-coil systems, and a variable air volume system

for the interior zones. The variable air volume system energy consumption

was used as the base for these comparisons.

Lake Santa Washington,

Charles Madison Nashville Maria Seattle DC

Dual-Duct vs VAV (Case 17 vs Case 9)

Cooling 1.13 1.06 1.10 1.00 0.99 1.17

Heating 3.51 1.65 2.54 11.83 3.31 3.19

Fan-Coil vs VAV (Case 20 vs Case 9)

Cooling 0.93 0.93 0.93 1.07 1.02 0.96

Heating 1.22 1.12 1.24 1.78 1.40 1.24

The much higher heating energy consumption for the dual-duct systems was explained in the previous section which dealt with outside air economy

cycles. This was exaggerated in these comparisons by the extremely low

heating energy consumption of the variable air systems in low heating

degree day areas. In most cities, the energy consumption of the fan-coil

unit systems compared closely with that of the variable air volume systems,

because both systems tried to provide the heating or cooling capacities to

match building loads. In comparing these two systems, the fan-coil system

minimizes the losses from mixing the hot and cold energy in the air-handling

system while giving up the benefit of using economy cycles. The relatively

higher cooling energy consumption of fan-coil systems in Santa Maria and

Seattle indicates the penalty of not using economy cycles for fan-coil

systems in mild weather areas.

D. Fan Energy Consumption

The fan pressure requirements of the air handling system simulations

performed in this study were given in the case descriptions. Several

arbitrary assumptions about pressures were made for these simulations.

Therefore, one should remember these assumptions when comparing the fan

energy consumptions of different systems and strategies. The fan energy

consumption ratios of the following table were selectively taken from

tables 7 through 12. The energy consumption of reheat systems is given a base value of 1.

13
Lake

Charles Madison Nashville

Santa

Maria Seattle

Washington

,

DC

RH (Case 1) 1.00 1.00 1.00 1.00 1.00 1.00

VAV (Case 9) 0.60 0.53 0.56 0.60 o.4y 0.47

Interior VAV , Perimeter Dual-Duct (Case 17)

1.03 1.04 1.04 1.00 1.03 1.03

Interior VAV , Perimeter Fan-coil (Case 20)

0.53 0.50 0.51 0.55 0.51 0.50

14
4. SUMMARY AND CONCLUSIONS

The comparative energy consumption of different air-handling systems was simulated for a large high-rise office building. This simulation was performed

for six cities representing various climatic conditions of the United States.

These cities have 65°F based heating and cooling degree days which range from

1498 to 7730 for heating and from 84 to 2739 for cooling. The air handling

systems simulated in the study included reheat, variable air volume, dual-duct

and fan-coil systems. The control strategies studied included three economy

cycles (temperature, return air, and enthalpy), two supply air temperature

resettings (by outside air temperature and by zone load demand), and the

combination of these strategies.

The total yearly energy consumption results for the different cities simulated

are presented in tables 1 through 6. The yearly energy consumption per unit

floor area and the relative comparisons are shown in tables 7 through 12.

Figures 3 through 50 depict these results correlated with cooling and heating

degree days.

Listed below are some of the major conclusions which can be drawn for this

large office building, based on the parameters used in the study.

A. Based on a comparison of cooling energy consumption alone, the enthalpy

economy cycle saved more than the return air economy cycle which, in turn, was better than the temperature economy cycle. At Santa Maria and Seattle

where the cooling degree days were low, the cooling savings from both the

enthalpy and return air economy cycles were similar.

B. Savings in cooling energy from using economy cycles were generally

accompanied by an increase in required heating energy. Therefore, decisions

to use economy cycles must be based on evaluating the overall savings of

both cooling and heating energies. The increase in heating energy also

depended on the type of air-handling system used. Dual-duct systems and

reheat systems used more than variable air volume systems.

C. Greater predicted energy savings were obtained by resetting the supply air

temperatures of both the hot and cold air in accordance with zone load

demands than by using the outside air temperature as a reference.

D. Resetting the supply air temperature reduced building energy consumption.

This strategy was especially beneficial when it was applied in combination

with the economy cycles

.

E. The energy consumptions of the variable air volume and fan-coil systems

were significantly below those of reheat and dual-duct systems. This

reflects the nature of the former two systems which try to match the system

capacities to the ever changing building loads. The differences in energy

consumptions of the variable air volume and fan-coil systems were relatively

small.

15
F. Substantial air transportation energy savings were obtained when variable

air volume and fan-coil systems were used. Dual-duct systems used more energy for transporting air than the other systems compared in this study.

It should be mentioned again that the energy consumption predictions presented

in this study were based on assumptions for a particular building using one

set of construction, orientation, and internal loads. The energy consumption

boundary of this study was at the energy inlets of the air handling systems.

Therefore, plant efficiencies, energy transmission losses, and energy costs

should also be considered in order to use the data given in this study for

control strategy selections and for preliminary design purposes.
REFERENCE

[1] Parken, W.H., Kao, J.Y., and Kelly, G.E., Strategies for Energy

Conservation in Small Office Buildings, U.S. National Bureau of Standards,

NBSIR 82-2489, June 1982.

[2] Kao, J.Y., Parken, W.H. , and Pierce, E.T., Strategies for Energy

Conservation for a Large Retail Store, U.S. National Bureau of Standards,

NBSIR 82-2580, September 1982.

[3] Nonresidential Buildings Energy Consumption Survey: Building

Characteristics, U.S. Department of Energy, DOE/E2A-0246 , March 1981.

[4] Hittle, D.C., The Building Loads Analysis System Thermodynamics (BLAST)

Program, Version 2.0: Users Manual, Technical Report E-153, U.S. Army

Construction Engineering Research Laboratory, Champaign, IL, June 1979.

[5] Grot, R.A., The Air Infiltration and Ventilation Rates in Two Large

Commercial Buildings, presented at ASHRAE 1983 Semiannual Meeting,

January 23-26, 1983.

[6] SOLMET Volume 1 - User’s Manual, Hourly Solar Radiation - Surface

Meteorological Observations, National Climatic Center, Ashville, NC,

August 1978.

[7] ASHRAE Handbook - 1981 Fundamentals Volume, Chapter 24, American Society

of Heating, Refrigerating, and Air-Conditioning Engineers, Inc.,

Atlanta, GA, 1981.

17
Table 1 . Annual Energy Consumption - Lake Charles , LA

Case Strategy

Heating Energy

Btu x 10 9 Cooling EnergyBtu x 10 9 Fan Energy

Btu x 10 9

1 Base RH 5.99 15.08 2.35

2 Base RH + temperature economy 6.51 13.53 2.35

3 Base RH + return air economy 7.47 13.71 2.35

4 Base RH + enthalpy economy 7.14 12.45 2.35

5 Base RH + supply air reset by

outside air 6.69 13.40 2.35

6 Base RH + supply air reset by zone cooling demand 5.56 11.29 2.35

7 Base RH + enthalpy economy + supply

air reset by zone cooling demand 3.45 9.52 2.35

8 Base VAV 0.46 8.32 1.41

9 Case 8 + enthalpy economy 0.49 7.09 1.40

10 Interior

Perimeter

base RH

base DD 5.25 14.28 2.58

11 Interior

Perimeter

base VAV

base DD 4.15 13.09 2.42

12 Interior

Perimeter

base RH + enthalpy economy

base DD + enthalpy economy 6.64 11.76 2.58

13 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy 4.47 10.94 2.41

14 Interior

Perimeter

base RH + enthalpy econmy

base DD + enthalpy economy +

hot deck reset by O.A. 3.18 8.63 2.58

15 Interior

Perimeter

Base VAV + enthalpy economy

Base DD + enthalpy economy +

hot deck reset by O.A. 2.11 8.31 2.41

16 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base DD + enthalpy economy +

hot and cold decks reset by

zone demand 2.78 3.31 2.58

17 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy +

hot and cold decks reset by zone demand 1.72 7.98 2.41

18 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base VAV + enthalpy economy 1.55 7.62 1.58

19 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

FC 1.63 6.92 1.41

20 Interior

Perimeter

base VAV + enthalpy economy

FC 0.56 6.60 1.24

18
Table 2. Annual Energy Consumption - Madison, W1

Case Strategy

Heating Energy

Btu x 109 Cooling EnergyBtu x 10 9 Fan EnergyBtu x 109

1 Base RH 9.41 10.57 2.85

2 Base RH + temperature economy 11.08 6.45 2.85

3 Base RH + return air economy 11.73 5.45 2.85

4 Base RH + enthalpy economy 11.66 5.26 2.85

5 Base RH + supply air reset by

outside air 8.26 8.68 2.85

6 Base RH + supply air reset by

zone cooling demand 5.77 6.81 2.85

7 Base RH + enthalpy economy + supply

air reset by zone cooling demand 8.00 3.85 2.85

8 Base VAV 4.07 4.31 1.53

9 Case 8 + enthalpy economy 4.09 2.83 1.52

10 Interior

Perimeter

base RH

base DD 9.29 10.27 3.15

11 Interior

Perimeter

base VAV

base DD 8.06 9.17 2.97

12 Interior

Perimeter

base RH + enthalpy economy

base DD -1- enthalpy economy 12.29 4.99 3.15

13 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy 9.53 4.65 2.96

14 Interior

Perimeter

base RH + enthalpy econmy

base DD + enthalpy economy +

hot deck reset by O.A. 10.24 3.39 3.15

15 Interior

Perimeter Base VAV + enthalpy economy

Base DD + enthalpy economy +

hot deck reset by O.A. 7.99 3.24 2.96

16 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base DD + enthalpy economy +

hot and cold decks reset by

zone demand 9.05 3.14 3.15

17 Interior

Perimeter

base VAV -1- enthalpy economy

base DD + enthalpy economy +

hot and cold decks reset by zone demand 6.76 2.99 2.96

18 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base VAV + enthalpy economy 6.52 2.97 1.71

19 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

FC 7.03 2.78 1.61

20 Interior

Perimeter

base VAV + enthalpy economy

FC 4.59 2.63 1.42

19
Table 3. Annual Energy Consumption - Nashville, TN

Case Strategy

Heating Energy

Btu x 10 9 Cooling EnergyBtu x 10 9 Fan Energy

Btu x 10 9

1 Base RH 7.09 13.17 2.58

2 Base RH + temperature economy 8.17 10.08 2.58

3 Base RH + return air economy 8.97 9.23- 2.58

4 Base RH + enthalpy economy 8.77 8.71 2.58

5 Base RH + supply air reset by

outside air 5.94 11.31 2.58

6 Base RH + supply air reset by

zone cooling demand 3.37 9.21 2.58

7 Base RH + enthalpy economy + supply

air reset by zone cooling demand 4.89 6.27 2.58

8 Base VAV 1.35 6.08 1.47

9 Case 8 + enthalpy economy 1.37 4.82 1.46

10 Interior

Perimeter

base RH base DD 6.61 12.58 2.85

11 Interior

Perimeter

base VAV

base DD 5.45 11.41 2.69

12 Interior

Perimeter

base RH + enthalpy economy

base DD + enthalpy economy 8.79 8.26 2.85

13 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy 6.21 7.71 2.68

14 Interior

Perimeter

base RH + enthalpy econmy

base DD + enthalpy economy +

hot deck reset by O.A. 5.94 5.92 2.85

15 Interior

Perimeter

Base VAV + enthalpy economy

Base DD + enthalpy economy +

hot deck reset by O.A. 4.30 5.69 2.68

16 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base DD + enthalpy economy +

hot and cold decks reset by zone demand 5.09 5.55 2.85

17 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy +

hot and cold decks reset by zone demand 3.48 5.32 2.68

18 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base VAV + enthalpy economy 2.93 5.05 1.63

19 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

FC 3.27 4.73 1.49

20 Interior

Perimeter

base VAV + enthalpy economy

FC 1.70 4.50 1.32

20
Table 4. Annual Energy Consumption - Santa Marla, CA

Case Strategy

Heating Energy

Btu x 10® Cooling Energy

Btu x 10® Fan Energy

Btu x 10®

1 Base RH 4.98 10.04 1.79

2 Base RH + temperature economy 6.21 7.79 1.79

3 Base RH + return air economy 7.52 4.25 1.79

4 Base RH + enthalpy economy 7.51 4.32 1.79

5 Base RH -1- supply air reset by

outside air 3.61 8.47 1.79

6 Base RH + supply air reset by

zone cooling demand 2.65 7.66 1.79

7 Base RH + enthalpy economy + supply

air reset by zone cooling demand 4.36 3.30 1.79

8 Base VAV 0.30 4.69 1.08

9 Case 8 + enthalpy economy 0.36 2.56 1.07

10 Interior

Perimeter

base RH

base DD 4.67 9.67 1.95

11 Interior

Perimeter

base VAV

base DD 3.57 8.57 1.81

12 Interior

Perimeter

base RH + enthalpy economy

base DD + enthalpy economy 7.63 4.11 1.95

13 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy 7.13 3.83 1.79

14 Interior

Perimeter

base RH + enthalpy econmy

base DD + enthalpy economy +

hot deck reset by O.A. 6.26 3.16 1.95

15 Interior

Perimeter Base VAV + enthalpy economy

Base DD + enthalpy economy +

hot deck reset by O.A. 5.36 3.02 1.79

16 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base DD + enthalpy economy +

hot and cold decks reset by zone demand 4.47 2.70 1.95

17 Interior

Perimeter

base VAV + enthalpy economy

base DD -4- enthalpy economy +

hot and cold decks reset by

zone demand 4.26 2.57 1.79

18 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base VAV + enthalpy economy 2.08 2.69 1.22

19 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

FC 2.35 2.88 1.13

20 Interior

Perimeter

base VAV + enthalpy economy

FC 0.64 2.75 0.98

21
Table 5. Annual Energy Consumption - Seattle, WA

Case Strategy

Heating Energy

Btu x 109 Cooling Energy

Btu x 109 Fan Energy

Btu x 109

1 Base RH 7.16 10.03 2.48

2 Base RH + temperature economy 8.86 4.89 2.48

3 Base RH + return air economy 9.68 2.76 2.48

4 Base RH + enthalpy economy 9.68 2.78 2.48

5 Base RH + supply air reset by

outside air 6.22 8.14 2.48

6 Base RH + supply air reset by zone cooling demand 3.40 6.22 2.48

7 Base RH + enthalpy economy + supply

air reset by zone cooling demand 5.79 1.89 2.48

8 Base VAV 1.62 3.65 1.22

9 Case 8 + enthalpy economy 1.64 1.48 1.21

10 Interior

Perimeter

base RH

base DD 6.92 9.69 2.71

11 Interior

Perimeter

base VAV

base DD 5.76 8.58 2.57

12 Interior

Perimeter

base RH + enthalpy economy

base DD + enthalpy economy 10.21 2.63 2.71

13 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy 7.88 2.46 2.55

14 Interior

Perimeter

base RH + enthalpy econmy

base DD + enthalpy economy +

hot deck reset by O.A. 8.56 1.87 2.71

15 Interior

Perimeter

Base VAV + enthalpy economy

Base DD + enthalpy economy +

hot deck reset by O.A. 6.97 1.79 2.55

16 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base DD + enthalpy economy +

hot and cold decks reset by zone demand 7.13 1.54 2.71

17 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy +

hot and cold decks reset by zone demand 5.43 1.46 2.55

18 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base VAV + enthalpy economy 3.81 1.56 1.37

19 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

FC 4.47 1.59 1.42

20 Interior

Perimeter

base VAV + enthalpy economy

FC 2.30 1.51 1.25

22
Table 6. Annual Energy Consumption - Washington, D.C.

Case Strategy

Heating Energy Cooling Energy

Btu x lO^ Btu x 10^

Fan Energy

Btu x 10^

1 Base RH 7.80 12.29 2.74

2 Base RH + temperature economy 9.05 8.37 2.74

3 Base RH + return air economy 9.82 7.54 2.74

4 Base RH + enthalpy economy 9.68 7.12 2.74

5 Base RH + supply air reset by

outside air 6.76 10.37 2.74

6 Base RH + supply air reset by

zone cooling demand 3.98 8.28 2.74

7 Base RH + enthalpy economy + supply

air reset by zone cooling demand 5.91 5.24 2.74

8 Base VAV 1.97 5.19 1.31

9 Case 8 + enthalpy economy 1.99 3.78 1.30

10 Interior

Perimeter

base RH

base DD 7.36 11.75 3.01

11 Interior

Perimeter

base VAV

base DD 6.17 10.59 2.85

12 Interior

Perimeter

base RH + enthalpy economy

base DD + enthalpy economy 9.84 6.73 3.01

13 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy 7.15 6.26 2.83

14 Interior

Perimeter

base RH + enthalpy econmy

base DD + enthalpy economy +

hot deck reset by O.A. 7.40 4.72 3.01

15 Interior

Perimeter Base VAV + enthalpy economyBase DD + enthalpy economy +

hot deck reset by O.A. 5.45 4.52 2.83

16 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

base DD + enthalpy economy +

hot and cold decks reset by zone demand 6.35 4.43 3.01

17 Interior

Perimeter

base VAV + enthalpy economy

base DD + enthalpy economy +

hot and cold decks reset by zone demand 4.43 4.24 2.83

18 Interior

Perimeter

base RH -1- enthalpy economy +

supply air reset by zone demand

base VAV + enthalpy economy 3.87 3.98 1.47

19 Interior

Perimeter

base RH + enthalpy economy +

supply air reset by zone demand

FC 4.36 3.81 1.55

20 Interior

Perimeter

base VAV + enthalpy economy

FC 2.47 3.61 1.37

23
Table 7. Comparative Annual Energy Consumption - Lake Charles, LA

Heating Energy Cooling Energy Fan Energy

Consumption, 10^ Btu/ft^

Case Strategy Ratio-Relative to Case 1

1 Base RH 24.97 62.84 9.87 1.00 1.00 1.00

2 Base RH + temperautre economy 27.13 56.38 9.78

1.09 0.90 1.00

3 Base RH + return air economy 31.12 57.12 9.78

1.25 0.91 1.00

4 Base RH + enthalpy economy 29.77 51.86 9.78

1.19 0.83 1.00

5 Base RH + supply air reset by 19.52 55.84 9.78

outside air 0.78 0.89 1.00

6 Base RH + supply air reset by 10.65 47.05 9.78

zone cooling demand 0.43 0.75 1.00

7 Base RH + enthalpy economy + supply 14.35 39.60 9.78

air reset by zone cooling demand 0.57 0.63 1.00

8 Base VAV 1.92 34.65 5.88

0.08 0.55 0.60

9 Case 8 + enthalpy economy 2.02 29.55 5.85

0.08 0.47 0.60

10 Interior base RH 22.75 59.50 10.76

Perimeter base DD 0.88 0.94 1.10

11 Interior base VAV 17.30 54.52 10.07

Perimeter base DO 0.69 0.87 1.03

12 Interior base RH + enthalpy economy 27.68 49.00 10.76 Perimeter base DD + enthalpy economy 1.11 0.78 1.10

13 Interior base VAV + enthalpy economy 19.45 45.58 10.04

Perimeter base DD + enthalpy economy 0.78 0.73 1.03

14 Interior base RH + enthalpy econmy 13.23 35.98 10.76

Perimeter base DD + enthalpy economy +

hot deck reset by O.A. 0.53 0.57 1.10

15 Interior Base VAV + enthalpy economy 8.80 34.62 10.04 Perimeter Base DD + enthalpy economy +

hot deck reset by O.A. 0.35 0.55 1.03

‘ 16 Interior base RH + enthalpy economy + 11.58 34.60 10.76

supply air reset by zone demand 0.46 0.55 1.10

Perimeter base DD + enthalpy economy +

hot and cold decks reset by

zone demand

17 Interior base VAV + enthalpy economy 7.15 33.25 10.04

Perimeter base DD + enthalpy economy +

hot and cold decks reset by zone demand

0.29 0.53 1.03

18 Interior base RH + enthalpy economy + 6.46 31.73 6.57 supply air reset by zone demand 0.26 0.50 0.67

Perimeter base VAV + enthalpy economy

19 Interior base RH + enthalpy economy + 6.79 28.85 5.89

supply air reset by zone demand 0.27 0.46 0.60

Perimeter FC

20 Interior base VAV + enthalpy economy 2.35 27.49 5.17 Perimeter FC 0.09 0.44 0.53

24
Table 8. Comparative Annual Energy Consumption, Madison, WI

Case Strategy

Heating Energy Cooling Energy Fan Energy

Consumption, 10^ Btu/ft^

Ratio-Relative to Case 1

1 Base RH 39.20 44.02 11.89

1.00 1.00 1.00

2 Base RH + temperature economy 46.18 26.87 11.89

1.18 0.61 1.00

3 Base RH + return air economy 48.88 22.70 11.89

1.28 0.52 1.00

4 Base RH + enthalpy economy 48.58 21.90 11.89

1.24 0.50 1.00

5 Base RH + supply air reset by 24.43 36.17 11.89

outside air 0.88 0.82 1.00

6 Base RH + supply air reset by 24.05 28.39 11.89 zone cooling demand 0.61 0.64 1.00

7 Base RH + enthalpy economy + supply 33.33 16.03 11.89

air reset by zone cooling demand 0.85 0.36 1.00

8 Base VAV 16.95 17.97 6.39

0.43 0.41 0.54

9 Case 8 + enthalpy economy 17.03 11.77 6.34

0.43 0.27 0.53

10 Interior base RH 38.71 42.80 13.11

Perimeter base DD 0.99 0.97 1.10

11 Interior base VAV 33.58 38.20 12.38

Perimeter base DD 0.86 0.87 1.04

12 Interior base RH + enthalpy economy 51.21 20.77 13.11

Perimeter base DD + enthalpy economy 1.31 0.47 1.10

13 Interior base VAV -1- enthalpy economy 39.71 19.37 12.33

Perimeter base DD + enthalpy economy 1.01 0.44 1.04

14 interior base RH + enthalpy econmy 42.67 14.13 13.11 Perimeter base DD -1- enthalpy economy + 1.09 0.32 1.10 hot deck reset by O.A.

15 Interior Base VAV + enthalpy economy 33.27 13.50 12.33

Perimeter Base DD + enthalpy economy + 0.58 0.31 1.04

hot deck reset by O.A.

.16 Interior base RH + enthalpy economy + 37.69 13.10 13.13

supply air reset by zone demand 0.96 0.30 1.10

Perimeter base DD + enthalpy economy +

hot and cold decks reset by zone demand

17 Interior base VAV + enthalpy economy 28.17 12.48 12.33

Perimeter base DD + enthalpy economy + 0.72 0.28 1.04

hot and cold decks reset by zone demand

18 Interior base RH + enthalpy economy + 27.18 12.39 7.12

supply air reset by zone demand 0.69 0.28 0.60

Perimeter base VAV + enthalpy economy

19 Interior base RH + enthalpy economy + 29.28 11.57 6.69

supply air reset by zone demand 0.75 0.26 0.56

Perimeter FC

20 Interior base VAV + enthalpy economy 19.13 10.95 5.91 Perimeter FC 0.49 0.25 0.50

25
Table 9. Comparative Annual Energy Consumption - Nashville, TN B

Heating Energy Cooling Energy Fan Energy

Consumption, 10 3 Btu/ft 2 Case Strategy Ratio--Relative to Case 1

1 Base RH 29.55 54.86 10.76

1.00 1.00 1.00

2 Base RH + temperature economy 34.05 41.98 10.76

1.15 0.77 1.00

3 Base RH + return air economy 37.35 38.44 10.76

1.26 0.70 1.00

4 Base RH + enthalpy economy 36.55 36.28 10.76

1.24 0.66 1.00

5 Base RH + supply air reset by 24.75 47.10 10.76 outside air 0.84 0.86 1.00

6 Base RH + supply air reset by 13.98 38.58 10.76

zone cooling demand 0.47 0.70 1.00

7 Base RH + enthalpy economy + supply 20.38 26.13 10.76 air reset by zone cooling demand 0.69 0.48 1.00

8 Base VAV 5.61 25.33 6.12

0.19 0.46 0.57

9 Case 8 + enthalpy economy 5.71 20.08 6.08

0.19 0.37 0.56

10 Interior base RH 27.53 52.42 11.86 Perimeter base DD 0.93 0.96 1.10

11 Interior base VAV 22.72 47.55 11.21 Perimeter base DD 0.77 0.87 1.04

12 Interior base RH + enthalpy economy 36.63 34.43 11.86

Perimeter base DD + enthalpy economy 1.24 0.63 1.10

13 Interior base VAV + enthalpy economy 25.89 32.11 11.17 Perimeter base DD + enthalpy economy 0.88 0.59 1.04

14 Interior base RH + enthalpy econmy 24.74 24.67 11.86

Perimeter base DD + enthalpy economy +

hot deck reset by O.A. 0.84 0.45 1.10

15 Interior Base VAV + enthalpy economy 17.92 23.72 11.17 Perimeter Base DD + enthalpy economy +

hot deck reset by O.A.

0.61 0.43 1.04

16 Interior base RH + enthalpy economy + 21.21 23.11 11.86

Perimeter

supply air reset by zone demand

base DD + enthalpy economy +

hot and cold decks reset by

zone demand

0.72 0.42 1.10

17 Interior base VAV + enthalpy economy 14.49 22.17 11.17 Perimeter base DD + enthalpy economy +

hot and cold decks reset by zone demand

0.49 0.40 1.04

18 Interior base RH + enthalpy economy + 12.23 21.03 6.78

supply air reset by zone demand 0.41 0.38 0.63

Perimeter base VAV + enthalpy economy

19 Interior base RH + enthalpy economy + 13.61 19.70 6.21 supply air reset by zone demand 0.46 0.36 0.58

Perimeter FC

20 Interior base VAV + enthalpy economy 7.10 18.76 5.52

Perimeter FC 0.24 0.34 0.51

26
Table 10. Comparative Annual Energy Consumption - Santa Marla, CA

Heating Energy Cooling Energy Fan Energy

Consumption, 10^ Btu/ft^

Case Strategy Ratio--Relative to Case 1

1 Base RH 20.75 41.81 7.45

1.00 1.00 1.00

2 Base RH + temperature economy 25.89 32.47 7.45

1.25 0.78 1.00

3 Base RH + return air economy 31.35 17.70 7.45

1.51 0.42 1.00

4 Base RH + enthalpy economy 31.30 18.02 7.45

1.51 0.43 1.00

5 Base RH + supply air reset by 15.03 35.28 7.45

outside air 0.72 0.84 1.00

6 Base RH + supply air reset by 11.05 31.90 7.45 zone cooling demand 0.53 0.76 1.00

7 Base RH + enthalpy economy + supply 18.16 13.75 7.45

air reset by zone cooling demand 0.88 0.33 1.00

8 Base VAV 1.26 19.55 4.52

0.06 0.47 0.61

9 Case 8 + enthalpy economy 1.51 10.67 4.45

0.07 0.26 0.60

10 Interior base RH 19.44 40.28 8.11

Perimeter base DD 0.94 0.96 1.09

11 Interior base VAV 14.86 35.71 7.53

Perimeter base DD 0.72 0.85 1.01

12 Interior base RH + enthalpy economy 31.80 17.11 8.11

Perimeter base DD + enthalpy economy 1.53 0.41 1.09

13 Interior base VAV + enthalpy economy 29.69 15.97 7.48

Perimeter base DD + enthalpy economy 1.43 0.38 1.00

14 Interior base RH + enthalpy econmy 21.90 13.15 8.11

Perimeter base DD + enthalpy economy +

hot deck reset by O.A.

1.06 0.31 1.09

15 Interior Base VAV + enthalpy economy 22.31 12.60 7.46

Perimeter Base DD + enthalpy economy +

hot deck reset by O.A.

1.08 0.30 1.00

• 16 Interior base RH + enthalpy economy + 18.61 11.26 8.13

supply air reset by zone demand 0.90 0.27 1.09

Perimeter base DD + enthalpy economy +

hot and cold decks reset by

zone demand

17 Interior base VAV + enthalpy economy 17.75 10.71 7.46

Perimeter base DD + enthalpy economy +

hot and cold decks reset by zone demand

0.86 0.26 1.00

18 Interior base RH + enthalpy economy + 8.65 11.22 5.09

supply air reset by zone demand 0.42 0.27 0.68

Perimeter base VAV + enthalpy economy

19 Interior base RH + enthalpy economy + 9.80 12.00 4.70

supply air reset by zone demand 0.47 0.29 0.63

Perimeter FC

20 Interior base VAV + enthalpy economy 2.65 11.45 4.07

Perimeter FC 0.13 0.27 0.55

27
Table 11. Comparative Annual Energy Consumption - Seattle, VA

Heating Energy Cooling Energy Fan Energy

Consumption, 10^ Btu/ft^

Case Strategy Ratio-Relative to Case 1

1 Base RH 29.83 41.80 10.33 1.00 1.00 1.00

2 Base RH + temperature economy 36.91 20.37 10.33

1.24 0.49 1.00

3 Base RH + return air economy 40.35 11.48 10.33

1.35 0.27 1.00

4 Base RH + enthalpy economy 40.33 11.58 10.33

1.35 0.28 1.00

5 Base RH + supply air reset by 25.92 33.90 10.33

outside air 0.87 0.81 1.00

6 Base RH + supply air reset by 14.17 25.91 10.33

zone cooling demand

.

0.47 0.62 1.00

7 Base RH + enthalpy economy + supply 24.12 7.87 10.33

air reset by zone cooling demand 0.81 0.19 1.00

8 Base VAV 6.74 15.20 5.10

0.23 0.36 0.49

9 Case 8 + enthalpy economy 6.85 6.15 5.02

0.23 0.15 0.49

10 Interior base RH 28.85 40.37 11.31 Perimeter base DD 0.97 0.97 1.10

11 Interior base VAV 23.98 35.75 10.69

Perimeter base DD 0.80 0.86 1.04

12 Interior base RH + enthalpy economy 42.55 10.95 11.31 Perimeter base DD + enthalpy economy 1.43 0.26 1.10

13 Interior base VAV + enthalpy economy 32.83 10.23 10.62

Perimeter base DD + enthalpy economy 1.10 0.24 1.03

14 Interior base RH + enthalpy econmy 35.68 7.81 11.29

Perimeter base DD + enthalpy economy +

hot deck reset by O.A.

1.20 0.19 1.09

15 Interior Base VAV + enthalpy economy 29.04 7.47 10.63 Perimeter Base DD + enthalpy economy +

hot deck reset by O.A.

0.97 0.18 1.03

16 Interior base RH + enthalpy economy + 29.71 6.43 11.29 supply air reset by zone demand 1.00 0.15 1.09 Perimeter base DD + enthalpy economy +

hot and cold decks reset by zone demand

17 Interior base VAV + enthalpy economy 22.61 6.09 10.63 Perimeter base DD + enthalpy economy +

hot and cold decks reset by zone demand

0.76 0.15 1.03

18 Interior base RH + enthalpy economy + 15.89 6.49 5.71 supply air reset by zone demand 0.53 0.16 0.55

Perimeter base VAV + enthalpy economy

19 Interior base RH + enthalpy economy + 18.64 6.63 5.91 supply air reset by zone demand 0.62 0.16 0.57

Perimeter FC

20 Interior base VAV + enthalpy economy 9.60 6.28 5.22

Perimeter FC 0.32 0.15 0.51

28
Table 12. Comparative Annual Energy Consumption - Washington, D.C.

Heating Energy Cooling Energy Fan Energy

Consumption, 10^ Btu/ft^

Case Strategy Ratio-Relative to Case 1

1 Base RH 32.51 51.20 11.42

1.00 1.00 1.00

2 Base RH + temperature economy 37.70 34.89 11.42

1.16 0.68 1.00

3 Base RH + return air economy 40.90 31.43 11.42

1.26 0.61 1.00

4 Base RH + enthalpy economy 40.34 29.81 11.42

1.24 0.58 1.00

5 Base RH + supply air reset by 28.15 43.22 11.42

outside air 0.87 0.84 1.00

6 Base RH + supply air reset by 16.58 34.52 11.42 zone cooling demand 0.51 0.67 1.00

7 Base RH + enthalpy economy + supply 24.60 21.81 11.42

air reset by zone cooling demand 0.76 0.43 1.00

8 Base VAV 8.20 21.62 5.45

0.25 0.42 0.48

9 Case 8 + enthalpy economy 8.28 15.76 5.40

0.25 0.31 0.47

10 Interior base RH 30.65 48.95 12.53

Perimeter base DD 0.94 0.96 1.10

11 Interior base VAV 25.70 44.14 11.85

Perimeter base DD 0.79 0.86 1.04

12 Interior base RH + enthalpy economy 40.98 28.03 12.53

Perimeter base DD + enthalpy economy 1.26 0.55 1.10

13 Interior base VAV + enthalpy economy 29.80 26.08 11.81

Perimeter base DD + enthalpy economy 0.92 0.51 1.03

14 Interior base RH + enthalpy econmy 30.81 19.66 12.54

Perimeter base DD + enthalpy economy +

hot deck reset by O.A. 0.95 0.38 1.10

15 Interior Base VAV + enthalpy economy 22.73 18.85 11.79

Perimeter Base DD + enthalpy economy +

hot deck reset by O.A. 0.70 0.37 1.03

. 16 Interior base RH + enthalpy economy + 26.45 18.47 12.54

supply air reset by zone demand 0.81 0.36 1.10

Perimeter base DD + enthalpy economy +

hot and cold decks reset by

zone demand

17 Interior base VAV -1- enthalpy economy 118.48 17.66 11.79

Perimeter base DD + enthalpy economy +

hot and cold decks reset by zone demand

0.57 0.34 1.03

18 Interior base RH + enthalpy economy + 16.14 16.57 6.12

supply air reset by zone demand 0.50 0.32 0.54

Perimeter base VAV + enthalpy economy

19 Interior base RH + enthalpy economy + 18.15 15.87 6.44

supply air reset by zone demand 0.56 0.31 0.56

Perimeter FC

20 Interior base VAV + enthalpy economy 10.28 15.06 5.72

Perimeter FC 0.32 0.29 0.50

29
Exterior wall:

spandrel glass, 2" (0.05 m) insulation K = 0.033 Btu/h*ft*°F

(0.057 W/m* °K) , and 1/2" (0.013 m) gypsum board.

Roof

:

built-up roof, 2" (0.05 m) insulation K = 0.033 Btu/h*ft*°F

(0.057 W/m*°K), 3 1/2" (0.09 m) lightweight concrete, metal deck,

air space, and 3/4" (0.019 m) ceiling panels.

Typical floor:

3 1/2" (0.09 m) concrete, air space, 3/4" (0.019 m) ceiling panels,

and carpet. 13' (3.96 m) floor to floor.

Partition

:

1/2" (0.013 m) gypsum board, air space, 1/2" (0.013 m) gypsum board.

Window:

single pane bronze plate, transmittance 0.24. light color Venetian

blind

.

Figure 1. Large office building model
Fraction

of

total

Fraction

of

total

<0- CM

CM

CMo

CM

00

SO

Vi CM 3 H O« O

oo

so

>s

cO T3

(U

CM

Mj- CMCM

CMO

CM

00

Es sO cO *—

1

•o3

-O’ 3

i—

1

Vl CO

CM 3 SO

i—

1

O

sc O CO rH •3

V4 00 3

u

CO sO CO

-O’

CM

4J • O r-f

COu

fa

CM

CM

CMO

CM

00iH

sO

t-H

-o- iHCM

iHO

r—

I

00

sO

CM

<0 T3

<U

0) 5

CM CM

'O’ CM

CM

CMo

CM00

SO

CM

00

SO

>.

CO TJc

3

co

cO T3

Vi3

4-1 cO CO

'0-

CM

Figure 2. Internal load profiles

31

I

Peak

lighting:

3.6

W/ft

^(38.8

W/m!

Peak

equipment:

0.5

W/ft

(5.4

W/m'

LIGHTING

AND

EQUIPMENT

SCHEDULES
Yearly

cooling

energy,

10 9

Btu

Yearly

cooling

energy,

10

Btu

CN

• 75.2

• 72.0

85.2

62.0

• 55.0

50.0

45.0

40.0

35.0

30.0

25.0

• 20.0

15.0

10 . 0

5.0

0.0

Cooling degree days

Figure 3. Cooling energy consumption of case 1 —base reheat

Cooling degree days

Figure 4. Cooling energy consumption of case 2 —base reheat

with temperature economy cycle

32

Yearly

cooling

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

cooling

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

Cooling degree days

Figure 5. Cooling energy consumption of case 3 —base reheat with

temperature economy cycle

Figure 6. Cooling energy consumption of case 4—--base reheat with

enthalpy economy cycle

33

Yearly

cooling

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

cooling

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

Cooling degree days

Figure 7. Cooling energy consumption of case 5 —base reheat with

supply air reset by outside air

Cooling degree days

Figure 8. Cooling energy consumption of case 6 —base reheat with

supply air reset by zone load demand

Yearly

cooling

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

cooling

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

CM

!>> 00

i-4 a)c

<u00e

•HO

O

a

rH

J-l nJa)

>-<

Cooling degree days

Figure 9. Cooling energy consumption of case 7 —base reheat with

enthalpy economy cycle and supply air reset by zone load

demand

Cooling degree days

Figure 10. Cooling energy consumption of case 8—base VAV

35
Figure 11. Cooling energy consumption of case 9 —base VAV with

enthalpy economy cycle

Figure 12. Cooling energy consumption of case 10—base RH for

interior zones, base DD for perimeter zones

36

Yearly

cooling

energy,

10 J

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

cooling

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

Figure 13. Cooling energy consumption of case 11 —base VAV for

interior zones, base DD for perimeter zones

Figure 14. Cooling energy consumption of case 12 —base RH with

enthalpy economy cycle for interior zones, base DD

with enthalpy economy cycle for perimeter zones

37

Yearly

cooling

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
CN

3

4-1 03 m

o

ao

<ue

<Uocco

o

(J

rH

V-i TO<u

Figure 15. Cooling energy consumption of case 13 —base VAV with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot deck reset by outside

air for perimeter zones

Figure 16. Cooling energy consumption of case 14 —base RH with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot deck reset by outside air

for perimeter zones

38
18 . 0

- 75.0

17.0-

16. 0— _ CDD CITY

3 15.0-

4J ~ 84 Santa Maria

CQ 14.0- ~ 129 Seattle

O' 13.0- O

" 460 Madison

rH 12.0- " 1415 Washington

« 11.0“ ‘ 1694 Nashville

00 10.0—

u

' 2739 Lake Charles

<Uc

a>bOc

•HrHOoa

rt

(U >> 1000 0000 2500 3000

3

4-1 PQ COo

Po

bO

a)c

0)bOc

•H

T—

(

o

oo

)-l CO

<u

>-•

Cooling degree days

Figure 17. Cooling energy consumption of case 15 —base VAV with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot deck reset by outside air

for perimeter zones

Figure 18. Cooling energy consumption of case 16 —base RH with

enthalpy economy cycle and supply air reset by zone demand for interior zones, base DD with enthalpy

economy cycle and hot - cold decks reset by zone demands for perimeter zones

39
Yearly

cooling

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

Cooling degree days

Figure 19. Cooling energy consumption of case 17 —base VAV with

enthalpy economy cycle for interior zones, base DD

with enthalpy economy cycle and hot-cold decks reset

by zone demands for perimeter zones

Figure 20. Cooling energy consumption of case 18 —base RH with

enthalpy economy cycle and supply air reset by zone demand for interior zones, base VAV with enthalpy

economy cycle for perimeter zones

40

Yearly

cooling

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Figure 21. Cooling energy consumption of case 19 —base RH with

enthalpy economy cycle and supply air reset by zone demand for interior zones, fan-coil for perimeter zi

Figure 22. Cooling energy consumption of case 20—base VAV with

enthalpy economy cycle for interior zones, fan-coil

for perimeter zones

41

Yearly

cooling

energy,

10

Btu/ft

03

Yearly

cooling

energy,

10

Btu/ft
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0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0

'

0

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8. 7. 6.

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6

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0

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cn

(3

(3

in

(\j

0

(3

C3

CVJ

(3

<3

in

(30

0

0

0

in

0

42

Cooling

degree

days

Figure

23.

Cooling

energy

consumption

of

cases

1

through

7

—

all

RH

cases
z33 '"33

e ot ‘ASxaua Suxxooo XiaeaA

0 0 0 0 0 0 0 0 0 0 0 0 o 0 0 o

in 0 in 0 in 0 in 0 in 0 in 0 in

0’

in 0 N N kfl in in XT m cn (\j H

n^g 01 ‘^Sjaua Suxxooo Xianaj.

43

500

1000

1500

2000

2500

3000

Cooling

degree

days

Figure

24.

Cooling

energy

consumption

of

cases

8

and

9

—

all

VAV

cases
3^3/^a

E 0I ‘A8aaua Suftooo X‘[ JE9A

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

in 0 in 0 in 0 in 0 in 0 in 0 in 0 in 0 N N in in in in 0 0 C\J cu rH rH

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

•0 •0 m N 0 in 0 0J rH 0 cn CD N 0 in 0 0 rH O

rH rH rH rH rH rH rH rH rH

0

0

0

0

CDID

(\J

0

0

CD0

0

0

in

rH

0

0

0

rH

0

0

in

n^g oi ‘48;iaua Sutiood Ax^ea^

44

Cooling

degree

days

Figure

25.

Cooling

energy

consumption

of

cases

11,

13,

15,

and

17

—

VAV

for

interior

zones,

DD

for

perimeter

zones
z*

3 '”TM

£

01 ‘ASaaua 2uf[°o:)

Q 0 G Q Q g G ® G Q G CD G G g G

in G in d in d in d in d in <3 in Q in d

N N 0) UD m in m m aj aj H H

G Q Q G G G G G Q G G G G G G G G G Q

m N d in T d ai tH Q cr> d N 0 in n a] t-H Q

rH rl rH rH tH H

G

G

Q

(T)

G

G

inai

g

q

Q

C\J

G

G

in

g

g

G

Q

G

in

G

nig 6 0I ‘^Saaua Sufiooo Axjeaj.

i

45

Cooling

degree

days

Figure

26.

Cooling

energy

consumption

of

cases

7,

9,

17,

and

20-

selected

case

comparisons
Yearly

heating

energy,

10

Btu

Yearly

heating

energy,

10

Btu

Heating degree days

Figure 27. Heating energy consumption of case 1 —base reheat

Heating degree days

Figure 28. Heating energy consumption of case 2 —base reheat

with temperature economy cycle

46

Yearly

heating

energy,

10

Btu/ft

Yearly

heating

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

heating

energy,

10

Btu

Figure 29. Heating energy consumption of case temperature economy cycle

3 —base reheat with

Heating degree days

Figure 30. Heating energy consumption of case 4 —base reheat with

enthalpy economy cycle

47

Yearly

heating

energy,

10

Btu/ft

Yearly

heating

energy,

10

Btu/ft
Heating degree days

CN

3

4J PQ

f*. ao

Vi

<Uc

<u60

(3 •H

•U

CO

(0 JC

>•.

i—

I

V

CO

(U

>-!

Figure 31. Heating energy consumption of case 5 —base reheat with

supply air reset by outside air

cO

QJ x:

r—

I

M

CO

(U >*

Figure 32. Heating energy consumption of case 6 —base reheat with

supply air reset by zone load demand

48
15 .

&

60.0 CN 3

•u PQ

CT\

00

QJc

cu00e

•HU

CO

0) 40

>-l cO

<U ><

14.0- ~ HDD CITY

13.0-

1498 Lake Charles

12.0- " 3053 Santa Maria

11.0- - 3696 Nashville

10.0- - 4211 Washington

9.0-

0.0-

5185

7730

Seattle

Madison

1000 2000 3000 4000 5000 6000

Heating degree days

7000 0000

C

Figure 33. Heating energy consumption of case 7

-—base reheat with

enthalpy economy cycle and supply air reset by zone lo;

demand

Heating degree days

Figure 34. Heating energy consumption of case 8 —base VAV

49

Yearly

heating

energy,

lCr

Btu/ft

o.

Yearly

heating

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

heating

energy,

10

Btu

Figure 35. Heating energy consumption of case 9 —base VAV with

enthalpy economy cycle

Heating degree days

Figure 36. Heating energy consumption of case 10 —base RH for

interior zones, base DD for perimeter zones

50

Yearly

heating

energy,

IQ 3

Btu/ft

2

Yearly

heating

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

heating

energy,

10

Btu

Figure 37. Heating energy consumption of case ll--base VAV for

interior zones, base DD for perimeter zones

Heating degree days

Figure 38. Heating energy consumption of case 12 —base RH with

enthalpy economy cycle for interior zones , base DD

with enthalpy economy cycle for perimeter zones

51

Yearly

heating

energy,

10

Btu/ft

Yearly

heating

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

heating

energy,

10

Btu

Figure 39. Heating energy consumption of case 13 —base VAV with

enthalpy economy cycle for interior zones, base DD wi

enthalpy economy cycle and hot deck reset by outside

air for perimeter zones

Figure 40. Heating energy consumption of case 14 —base RH with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot deck reset by outside air

for perimeter zones

52

Yearly

heating

energy,

10

Btu/ft

Yearly

heating

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

^

Yearly

heating

energy,

10

Btu

41. Heating energy consumption of case 15 —base VAV with

enthalpy economy cycle for interior zones, base DD with

enthalpy economy cycle and hot deck reset by outside air

for perimeter zones

Figure 42. Heating energy consumption of case 16 —base RH with

enthalpy economy cycle and supply air reset by zone demand for interior zones, base DD with enthalpy

economy cycle and hot - cold decks reset by zone demands for perimeter zones

53
Figure 43. Heating energy consumption of case 17 —base VAV with

enthalpy economy cycle for interior zones, base DD

with enthalpy econony cycle and hot-cold decks reset

by zone demands for perimeter zones

Heating degree days

Figure 44. Heating energy consumption of case 18 —base RH with

enthalpy economy cycle and supply air reset by zone demand for interior zones, base VAV with enthalpy

economy cycle for perimeter zones

54
Yearly

heating

energy,

10

Btu

£

Yearly

heating

energy,

10

Btu

15 . 0

- 60 .

0

CNl 14.0

13.0

12 . 11 . 10 . 9 . e.7 . 6 . 5 . 4 . 3 . 2 .

1 .

0

0 . 0

- 1000

gure 45.

HDD CITY

1498 Lake Charlei

3053 Santa Maria

3696 Nashville

4211 Washington

5185 Seattle

7730 Madison

2000 3000 4000 5000 6000

Heating degree days

7000

55.0

50.0

45.0

40.0

35.0

30.0

25.0

20.0

15.0

10.0

5.0

0.0

a

6000

Heating energy consumption of case 19—base RH with

enthalpy economy cycle and supply air reset by zone demand for interior zones, fan-coil for perimeter zones

Heating degree days

Figure 46. Heating energy consumption of case 20 —base VAV with

enthalpy economy cycle for interior zones, fan-coil

for perimeter zones

55

Yearly

heating

energy,

10

Btu/ft

Yearly

heating

energy,

10

Btu/ft
^3j/ n:ig ^_qT ‘ASaaua Suf^Baq Xx-iEa^

0 0 q 0 0 0 0 0 0 0 0 0

<3 in q in 0 in 0 in 0 in 0 in 0

<U in in n ro oj (\j H H

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

in cn CVJ tH 0 CD N CO in * cn ft] T-t Q

mg oi ‘^S-isua Surreal} Ax^na^

6

56

Heating

degree

days

Figure

47.

Heating

energy

consumption

of

cases

1

through

7

—

all

RH

cases
£.01 ‘4g;iaua Su-Heaq Aqaea^

0 0 0 0 0 0 0 0 0 0 0 0 0

0 in 0 in 0 in 0 in 0 in 0 in 0

U3 in in m- m m 0J N rl H

in^nN'HQcnraNUDin^nojrH© rH tH tH tH t-H

n^a OT ‘^*9U9 Su-f^Baq Aianax

57

000

2000

3000

4000

5000

6000

7000

8000

Heating

degree

days

Figure

48.

Heating

energy

consumption

of

cases

8

and

9

—

all

VAV

cases
qj/nrjg QI ‘Xgaaua guxrjaaq Xx^Ba^

3 0

0 0 0 0 0 0 0 0 0 0 0 0 0

0 to* 0 10 0 to* 0 to 0 to 0 to 0

0 to to n cn OJ OJ H rH 0

0

0

(D

0

0

N

0

0

Q

UD

0

0

0

10

0

0

0

<1

0

0

0

cn

0

0

0

OJ

0

0

0

10

rH rH rotH oj 0 oo 0 0 to (D OJ 0

nxg 01 ‘Xgjaua girpneaq Xx^a^

6

58

Heating

degree

days

Figure

49.

Heating

energy

consumption

of

cases

11,

13,

15,

and

17

—

VAV

for

interior

zones,

DD

for

perimeter

zones
e 0T ‘ASaaua SuT^Baq Ajjlwx

I o

CM

"3c

to

<Js

o

LO

<uM

3

bD

•H

nng
NBS») I4A irev. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 83-2746

2. Performing Organ. Report No 3. Publication Date

July 1983

4. TITLE AND SUBTITLE

Strategies for Energy Conservation for a Large Office Building

5. AUTHOR(S)

James Y. Kao

6. PERFORMING ORGANIZATION (If joint or other than NBS, see in struction s) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

Office of Building Energy Research and Development

Office of Conservation and Renewable Energy

U.S. Department of Energy

Washington, DC 20585

10. SUPPLEMENTARY NOTES

1 Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bl iography or literature survey, mention it here)

A comparative analysis is made of the thermal performance of selected HVAC systems

and control strategies commonly employed in large office buildings. The comparisons

are made for six geographical locations representing wide Climatic variations within

the continental United States.

Hour-by-hour simulations with the BLAST computer program are used to obtain the

yearly heating, cooling, and fan energy consumption of a twelve-story large office

building. The HVAC systems simulated are constant volume reheat, variable air

volume, dual-duct, and fan-coil systems. The control strategies tested are dry

bulb temperature economy cycles, enthalpy economy cycle, supply air temperature

resetting, and the combinations of these strategies. The results of these simulations are presented and discussed. Substantial energy consumption differences are shown to exist.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) building control strategies; building energy conservation; building thermal

performance; HVAC systems

13. AVAILABILITY

|y~| Unlimited For Official Distribution. Do Not Release to NTIS

[^] Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

[7C] Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

69

15. Price

$ 10.00

USCOMM-DC 6043-P80