NATL INST. OF STAND & TECH

AlllOb 2b0357

Reference

NBS

Publications

NBSIR 84-2831

Strategies for Energy Conservation

for A School Building

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, DC 20234

March 1 984

1 Prepared for Office of Building Energy Research and Development

Office of Conservation and Renewable Energy

S. Department of Energy

ashington, DC

100

,U36

34-2831

1934

v

i Oo

NBSIR 84-2831

STRATEGIES FOR ENERGY CONSERVATION

FOR A SCHOOL BUILDING

James V. Kao

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, DC 20234

March 1 984

Prepared for Office of Building Energy Research and Development

Office of Conservation and Renewable Energy

U.S. Department of Energy

Washington, DC

z

c o

o*

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

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director

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IT\

ABSTRACT

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

systems and control strategies commonly employed in education 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 an elementary school.

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

dual-duct, and unit ventilator systems. The control strategies tested are drybulb temperature economy cycle, 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.

Key words: school building control strategies; school building energy

conservation; school HVAC systems; school building thermal

performance

.

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.

iv
TABLE OF 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 and Weather Data 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 8

4. SUMMARY AND CONCLUSIONS 15

5. 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 26

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

vi
LIST OF FIGURES

Page

Figure 1. School building model 30

Figure 2. Classroom internal load profiles 31

Figure 3. Library internal load profiles 32

Figure 4. Office internal load profiles 33

Figure 5. Auditorium internal load profiles 34

Figure 6. Cafeteria internal load profiles 35

Figure 7. Gymnasium internal load profiles 36

Figure 8. Cooling and heating energy consumption of case 1 (classrooms and offices) — base reheat 37

Figure 9. Cooling and heating energy consumption of case 2 (classrooms and offices) — base reheat with temperature

economy cycle 38

Figure 10. Cooling and heating energy consumption of case 3

(classrooms and offices) — base reheat with enthalpy

economy cycle 39

Figure 11. Cooling and heating energy consumption of case 4

(classrooms and offices) — base reheat with supply air

temperature reset by zone load demand 40

Figure 12. Cooling and heating energy consumption of case 5 (classrooms and offices) — base reheat with enthalpy

economy and supply air temperature reset by zone

load demand 41

Figure 13. Cooling and heating energy consumption of cases 1 through 5 (classrooms and offices) — all reheat cases 42

Figure 14. Cooling and heating energy consumption of case 6

(classrooms and offices) — base variable air volume 43

Figure 15. Cooling and heating energy consumption of case 7 (classrooms and offices) — base variable air volume with

temperature economy cycle * 44

Figure 16. Cooling and heating energy consumption of case 8

(classrooms and offices) — base variable air volume with

enthalpy economy cycle 45

vii
LIST OF FIGURES

Page

Figure 17. Cooling and heating energy consumption of case 9

(classrooms and offices) — base variable air volume with

supply air temperature reset by zone load demand 46

Figure 18. Cooling and heating energy consumption of case 10

(classrooms and offices) — base variable air volume with

enthalpy economy cycle and supply air temperature reset by zone load demand 47

Figure 19. Cooling and heating energy consumption of cases 6 through 10

(classrooms and offices) — all variable air volume cases ... 48

Figure 20. Cooling and heating energy consumption of case 11

(classrooms and offices) — base dual-duct 49

Figure 21. Cooling and heating energy consumption of case 12

(classrooms and offices) — base dual-duct with enthalpy

economy cycle 50

Figure 22. Cooling and heating energy consumption of case 13

(classrooms and offices) — base dual-duct with enthalpy

economy cycle and hot air temperature reset 51

Figure 23. Cooling and heating energy consumption of case 14

(classrooms and offices) — base dual-duct with hot and cold

air temperature reset 52

Figure 24. Cooling and heating energy consumption of cases 11 through 14

(classrooms and offices) — all dual-duct cases 53

Figure 25. Cooling and heating energy consumption of case 15

(classrooms and offices) — unit ventilator system 54

Figure 26. Cooling and heating energy consumption of cases 5, 10, 14,

and 15 (classrooms and offices) 55

Figure 27. Cooling and heating energy consumption of case 16 (entire

school) — case 1 for classrooms and offices, base systems

for non-classroom/of f ice areas, all systems on for 10 hour

a day 56

Figure 28. Cooling and heating energy consumption of case 17 (entire

school) — case 1 for classrooms and offices, base systems

for non-classroom/office areas, all systems on according to

occupancy schedules 57

viii
LIST OF FIGURES

Page

Figure 29. Cooling and heating energy consumption of case 18 (entire

school) — case 3 for classrooms and offices, enthalpy

economy cycle for non-classroom/of f ice areas 58

Figure 30. Cooling and heating energy consumption of case 19 (entire

school) — case 5 for classrooms and offices, enthalpy

economy cycle for non-classroom/off ice areas 59

Figure 31. Cooling and heating energy consumption of case 20 (entire

school) — case 6 for classrooms and offices, base systems

for non-classroom/off ice areas ...» 60

Figure 32. Cooling and heating energy consumption of case 21 (entire

school) — case 8 for classrooms and offices, enthalpy

economy cycle for non-classroom/of f ice areas....... 61

Figure 33. Cooling and heating energy consumption of case 22 (entire

school) — case 10 for classrooms and offices, enthalpy

economy cycle for non-classroom/office areas 62

Figure 34. Cooling and heating energy consumption of case 23 (entire

school) — case 11 for classrooms and offices, base systems

for non-classroom/of f ice areas 63

Figure 35. Cooling and heating energy consumption of case 14 (entire

school) — case 13 for classrooms and offices, enthalpy

economy cycle for non-classroom/office areas 64

Figure 36. Cooling and heating energy consumption of case 25 (entire

school) — case 14 for classrooms and offices, enthalpy

economy cycle for non-classroom/of f ice areas 65

Figure 37. Cooling and heating energy consumption of case 25 (entire

school) case 15 for classrooms and offices, enthalpy

economy cycle for non-classroom/office areas 66

Figure 38. Cooling and heating energy consumption of cases 16 and 17

(entire school) 67
.
1. INTRODUCTION

This report is the fourth and last in a series of reports by researchers at the

National Bureau of Standards (NBS) which compare the energy consumption of

alternative heating, ventilating, and air-conditioning (HVAC) systems and control strategies for commercial and institutional buildings. The purpose of

this report, along with the three previous reports which studied a small office

building [1] , a large retail store [2], and a large office building [3], was

to generate comparative energy consumption data for various building types in

different geographical locations in the United States. These studies were

intended to derive general guidelines of air handling system control strategy

selections for building operators and designers. The results and conclusions

of these studies should aid the prospective users in making preliminary decisions about strategies for air-handling system controls in both new and renovative work. The present study specifically deals with an education building.

Although a large elementary school was used as the building sample, the study

results should be applicable to high school buildings of similar construction

and usage. The air handling systems and control strategies employed in this

study were those most commonly used for this type of building.

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, 2, and 3] 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 modeled building was a one-story elementary school. The total gross floor area was approximately 59,300 square feet (5,509 ra 3

). The classrooms, library,

and offices were located on the eastern part of the building. The non-classroom/office areas, such as auditorium, cafeteria, kitchen, and gymasium, were situated on the western part. There were 22 classrooms with a total floor

area of 21,500 square feet (1,997 m

3 ). The total floor area of the offices

was 6,400 square feet (5,946 m

3

) . The school population, including faculty

and students, was 860. The building dimensions, space arrangement, and other

pertinent building construction data are shown in figure 1.

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

Year (TMY) climatic tapes [5].

2.2 AIR HANDLING SYSTEM SIMULATION AND CONTROL STRATEGIES

The capacities of the air handling systems were sized to keep the space

temperature between 68°F (20.0°C) and 78°F (25.6°C) during occupied hours.

ASHRAE [6] 97.5 percent design dry-bulb temperature and 2.5 percent design drybulb/mean coincidence wet-bulb temperature were used in sizing system calculations. The night and weekend heating setback temperature was 55°F (12.8°C).

The air handling system fans ran continuously during occupied hours and ran intermittently during setback hours. It was assumed that both the cooling

and heating media (chilled and hot water) were available year-round. The

throttling rangeJL/ of the cooling coil controller was 3°F (1.7°C).

The daily occupancy, lighting, and equipment (in cafeteria) loadings and profiles

of the various spaces are shown in figures 2 through 6. At least 5 cfm (2.36 x

1CT3 m

3 /s) per person of outside air was used for ventilation calculations. The

kitchen had a total exhaust of 12 air changes per hour with the make-up air

coming from a heating and ventilating unit, the cafeteria and the halls.

Since the classrooms, offices, and the library were concentrated in the east

and central part of the building, they were simulated by using either two large

air handling systems or individual cooling type unit ventilators in each space.

The non-classroom/of f ice spaces — auditorium, cafeteria, kitchen, and gymnasium — were each supplied by an individual air handling system. These non- classroom/office spaces, with the exception of the kitchen, were air conditioned

by single-zone draw through systems having both heating and cooling coils.

The only control strategy used for these systems was the enthalpy economy

cycle. A heating and ventilating unit was provided for the kitchen heating

—

/

Throttling range is defined as the change required, in a proportional system,

in a controlled variable (such as air temperature) to move the controlled

device (such as a coil valve) from one of its extreme positions of travel to

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

2
and exhaust requirement. The classroom and office area were simulated by

four types of air handling systems commonly used for the schools. They were

the constant volume reheat, variable air volume, dual-duct, and cooling type

unit ventilators. The control strategies tested for the classroom area included

outside air economy cycles (both dry-bulb and enthalphy comparisons), cold and

hot air temperature reset and combination of these strategies. In one case (case 16), the air handling systems were in continuous operation for 10 hours

a day. In all the other cases, the air handling systems were in continuous

operation only during occupied hours. The energy consumption was simulated

for the entire year, although for most schools recess took place during summer

and Christmas periods. Details of the HVAC systems and control strategies are given in the following paragraphs. Cases 1 through 15 are for classrooms,

offices and the library. Case 16 through 27 are for the entire school.

A. Case 1 — Base Reheat (RH) System

Constant volume terminal reheat systems were used for the classroom, offices,

and library. The supply air temperature was 59 °F (15.0°C) which included the

fan heat gain. The amount of outside air was held constant at 20 percent of

the total supply air. The system serving the classrooms was in continuous

operation 7 hours a day. The system that supplied air to the library and

offices was in continuous operation 10 hours a day. The total pressure of the

supply air fans and return air fans were assumed to be 3.5 in. of water (8.7 x

lO^Pa) and 0.5 in. of water (1.2 x lO^Pa), respectively. Their efficiencies

were assumed to be 75 percent.

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

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

to above the setting of this sensor, the outside air damper was closed to its

minimum position of 20 percent of the supply air and the building cooling was accomplished entirely by the chilled water.

C. Case 3 — Reheat (RH) System with Enthalpy Economy Cycle

Enthalpy economy cycle was added to case 1. 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 system, provided 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 comparison was accomplished by having

enthalpy sensors in the return and outside air streams.

D . Case 4 — Reheat (RH) System with Supply Air Temperature Reset by Zone Load

Demand

Case 1 was modified to have variable supply air temperature. Zone temperature

sensors were simulated to reset the supply air temperature higher than 59 °F

(15°C) as determined by the zone having the highest cooling load. The supply

air temperature was limited to between 59°F (15°C) and 65°F (18.3°C).

3
E. Case 5 — Reheat (RH) System with Enthalpy Economy Cycle and Supply Air

Temperature Reset by Zone Load Demand

This case combined cases 3 and 4.

F. Case 6 — Base Variable Air Volume (VA) System

Variable air volume systems with terminal reheat coils were simulated for the

classrooms, offices and library. Terminal units for the perimeter zones were

provided with reheat coils. The minimum supply air of the terminal units were

set at 0.5 and 0.2 of the peak suppy air for classrooms and offices (including

library), respectively. The supply air fan pressure was assumed to be 4.0 in.

of water (1.0 x lO-^Pa) and inlet vanes were used for capacity throttling. The

supply air temperature was 59°F (15°C), the same as for the reheat system.

G. Case 7 — Variable Air Volume (VA) System with Temperature Economy Cycle

Temperature economy cycle was added to case 6.

H. Case 8 — Variable Air Volume (VA) System with Enthalpy Economy Cycle

Enthalpy economy cycle was added to case 6.

I. Case 9 — Variable Volume (VA) System with Supply Air Temperature Reset by

Zone Load Demand

The supply air temperature was allowed to vary between 59°F (15°C) and 65°F

(18.3°C) similar to the reheat system of case 4.

J . Case 10 — Variable Air Volume (VA) System with Enthalpy Economy Cycle and

Supply Air Temperature Reset by Zone Load Demand

This case combined cases 8 and 9.

K. Case 11 — Base Dual-Duct (DP) System

Dual-duct systems were used for the classrooms, offices and library. The dualduct systems had preheat coils in the mixed air stream with the main heating

and cooling coils in the hot and cold ducts. The cold air temperature was set

at 59°F (15°C) and the hot air temperature was set at 120°F (48.9°C). The

supply air fan pressure was assumed to be 4 in. of water (1.0 x lO-^Pa). The

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

the reheat system. The energy losses from mixing damper leakage were not

considered in this case and the other dual-duct cases.

L . Case 12 — Dual- Duct (DP) System with Enthalpy Economy Cycle

Enthalpy economy cycle was added to case 11.

4
M. Case 13 — Dual-Duct (DP) System with Enthalpy Economy Cycle and Hot Air

Temperature Reset

The hot air temperature of the dual-duct systems were reset by the outside

temperature. When the outside air temperature was 0°F (-17.8°C) and below, the

hot air temperature was 120°F (48.9°C) and when the outside air temperature was 70°F (21.1°C) and higher, the hot air temperature was 90°F (32.2°C). The hot

air temperature varied between 120°F (48.9°C) and 90°F (32.2°C) according to

the outside air temperature. Other than this reset schedule, the systems

operated the same as those of case 12.

N. Case 14 — Dual-Duct (DP) System with Fixed Outside Air and Reset of Both

Hot and Cold Air Temperature

The systems had fixed ventilation air during occupied hours. The hot air

temperature was reset as described in case 13 and the cold air temperature

was reset between 59°F (15°C) and 65°F (18.3°C) to satisfy the highest cooling

load zones.

O. Case 15 — Unit Ventilator (UV) System with Cooling

The thermal zones for the classrooms, offices, and library were simulated with

cooling type unit ventilators. The unit ventilators had heating and cooling

available year-round. The outside air dampers were capable of admitting 100

percent outside air. Room temperature sensors controlled the heating coil

valves, the dampers, and the cooling coil valves to maintain the space

temperature.

P . Case 16 — Case 1 for Classrooms and Offices, Draw-Through Systems with

Minimum Ventilation Air for Non-classroom/of f ice Spaces — All Systems On

for 10 Hours a Day

As described previously, the non-classroom/of f ice spaces which included the

auditorium, cafeteria, kitchen, and gymnasium, had draw-through type units.

The kitchen system had no cooling capability and its outside air dampers were

fully open when the system was on. All other systems served the auxiliary

spaces had cooling coils to supply a fixed air temperature of 59°F (18.3°C).

All systems in this case ran 10 hours a day regardless of their occupancy

schedules

.

Q. Case 17 — Case 1 for Classrooms and Offices, Draw-Through Systems with

Minimum Ventilation Air for Non-classroom/office Spaces (Base) — All

Systems On According to their Occupancy Schedules

This case was similar to case 16 above except that the system operation

schedules during school days followed the individual occupancy schedules of

the spaces. The classroom, office (including library), auditorium, cafeteria

and kitchen, and gymnasium systems were operating 7, 10, 3, 6, and 7 hours,

respectively. This case is used as the base case in tables 7 through 12 for

comparing the energy consumption of the entire school.

5
R. Case 18 — Case 3 for Classrooms and Offices, Enthalpy Economy Cycle Added

to Systems Serving Non-classroom/office Spaces

The base reheat systems of the classrooms and offices were combined with the

non-classroom/office systems, all under enthalpy economy cycles.

S . Case 19 — Case 5 for Classrooms and Offices, Enthalpy Economy Cycles Added

to Systems Serving Non-classroom/office Spaces

The classroom and office reheat systems with supply air temperature reset were

combined with the non-classroom/of f ice systems, all under enthalpy economy

cycle.

T. Case 20 — Case 6 for Classrooms and Offices, Base Systems for

Non-classroom/office Spaces

The classroom and office base variable air volume systems were combined with

the non-classroom office systems.

U . Case 21 — Case 8 for Classrooms and Offices, Enthalpy Economy Cycle Added

to Systems Serving Non-classroom/office Spaces

The classroom and office variable air volume systems were combined with the

non-classroom/of f ice systems, all under enthalpy economy cycle.

V . Case 22 — Case 10 for Classrooms and Offices, Enthalpy Economy Cycle Added

to Systems Serving Non-classroom/of f ice Spaces

The classroom and office variable air volume systems with supply air temperature

reset were combined with the non-classroom/of f ice systems, all under enthalpy

economy cycle.

W. Case 23 — Case 11 for Classrooms and Offices, Base System for

Non-classroom/of f ice Spaces

The classroom and office base dual-duct systems were combined with the

non-classroom/office systems.

X. Case 24 — Case 13 for Classrooms and Offices, Enthalpy Economy Cycle Added

to Systems Serving Non-classroom/office Spaces

The classroom and office dual-duct systems with hot air temperature reset were combined with the non-classroom/of f ice systems, all under enthalpy economy

cycle

.

Y . Case 25 — Case 14 for Classrooms and Offices, Enthalpy Economy Cycle Added

to Systems Serving Non-classroom/office Spaces

The classrooms and office dual-duct system with hot and cold air temperature

reset were operated with the minimum amount of ventilation air. The systems

6
serving the non-classroom/office spaces were operated under enthalpy economy

cycle.

Z. Case 26 — Case 15 for Classrooms and Offices, Enthalpy Economy Cycle Added

to Systems Serving Non-classroom/office Spaces

The classrooms and offices were simulated with individual cooling type unit

ventilators as described in case 15. The systems serving the non-classroom/

office spaces were operated under enthalpy economy cycle.

7
3. RESULTS AND DISCUSSION

3.1 ENERGY CONSUMPTION RESULTS

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

from diferent systems, strategies, and combination 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 gross floor area of the systems served. Tables 7 through 12 also give

the comparative energy consumption data normalized to the consumption of a base

case. Cases 1 through 15 are for classrooms and offices (including library)

only and the base reheat systems (case 1) is used as the base case. Cases 16

through 26 are for the entire school and case 17 is used as the base case. As

described previously, case 17 had reheat systems for the classrooms and offices

(including library) and single-zone, draw-through type systems for the

non-classroom/office spaces, all operated according to the space occupancy

schedules

.

The yearly cooling and heating energy consumption results are also plotted

against the cooling and heating degree days in figures 8 through 38. The reasons for using the 65°F (18.3°C) base degree days was given in references 2 and 3. The cooling and heating energy consumption data points of each case are fitted with a least-squares line. Figures 8 through 12 show the classroom and

office area under the reheat systems. Figure 13 is a comparison of figures 8

through 12. Figures 14 through 18 and figures 20 through 23 are for variable

air volume systems and dual-duct systems, respectively. Figures 19 and 24

show the various control strategies applied to these two systems, respectively.

Figure 25 shows the energy consumption of unit ventilators for the classrooms

and offices. Figure 26 puts four cases together for comparison—one case for

each of the four systems. Figure 27 through 37 show the yearly cooling and

heating energy consumption of cases 16 through 26 of the entire school. Fig- ure 38 has cases 16 and 17 together on the same charts to compare the energy

consumption of the entire school when the air-handling systems were operating

under different schedules.

3.2 COMPARISON OF STRATEGIES

A. Outside Air Economy Cycles

Two outside air economy cycles were applied to the reheat and variable air

volume systems. The temperature economy cycle mixed the outside air and return

air in order to maintain the temperature of the supply air setting. The enthalpy

economy cycle compared the enthalpies of the outside air and return air to

admit the minimum amount of ventilation air only when the outside air enthalpy

was higher than that of the return air. Otherwise the outside air damper

position was so determined that the mixed air temperature would not fall

below the supply air temperature setting. The dual-duct system used for the

classrooms and offices, and the single-zone draw-through systems used for the

non-classroom/of f ice spaces were also simulated with enthalpy economy cycle.

The table lists the annual energy consumption ratios of various economy cycles

of the six cities.

8
Table Showing Cooling and Heating Energy Consumption Ratios of Economy Cycles

Lake

Charles Madison Nashville

Santa

Maria Seattle

Washington,

DC

Cooling

Degree Days 2739 460 1694 84 129 1415

RH with Temperature Economy (Case 2)/Base RH (Case 1) , Classrooms & Offices

Cooling 0.92 0.68 0.80 0.87 0.52 0.73

Heating 1.02 1.02 1.02 1.02 1.02 1.02

RH with Enthalpy Economy (Case 3)/Base RH (Case 1), Classrooms & Offices

Cooling 0.85 0.53 0.69 0.46 0.25 0.61

Heating 1.03 1.02 1.01 1.07 1.03 1.03

VA with Temperature Economy (Case 7)/Base VA (Case 6) , Classrooms & Offices

Cooling 0.98 0.93 0.95 0.92 0.72 0.92

Heating 1.01 1.00 1.00 1.01 1.00 1.00

VA with Enthalpy Economy (Case 8)/Base VA (Case 6), Classrooms & Offices

Cooling 0.94 0.80 0.88 0.56 0.41 0.84

Heating 1.02 1.00 1.01 1.03 1.00 1.00

DD with Enthalpy Economy (Case 12) /Base DD (Case 11), Classrooms & Offices

Cooling 0.86 0.56 0.71 0.46 0.26 0.63

Heating 1.15 1.10 1.17 1.27 1.15 1.15

RH with Enthalpy Economy (Case 18) /Base RH (Case 17), Entire School

Cooling 0.86 0.55 0.71 0.47 0.26 0.63

Heating 1.03 1.02 1.03 1.06 1.05 1.03

VA with Enthalpy Economy (Case 21)/Base VA(Case 20), Entire School

Cooling 0.94 0.81 0.89 0.56 0.43 0.86

Heating 1.01 1.00 1.00 1.02 1.01 1.00

RH = reheat

VA = variable air volume

DD = dual-duct

In almost all cases, the percentage of cooling energy savings were higher in

low cooling degree day areas, such as Seattle, Santa Maria, and Madison. The

only exception was in Santa Maria, when temperature economy cycle was applied

to reheat systems (case 2 vs case 1), more cooling savings were achieved in

Washington, D.C. and Nashville than that of Santa Maria. This was caused by the

low setting of the 59 °F (15°C) discharge air temperature which eliminated a larger portion of the available free-cooling time in Santa Maria. The percentage of heating energy increase caused by the economy cycles were rather small,

except for the dual-duct cases. This small increase of heating energy was quite different from the results of other type of buildings [1, 2, 3]. This

9
phenomenon can be traced to the heavy internal load of the classrooms which

reduced the heating energy consumed and benefitted from the free-cooling of the

economy cycles. The results also indicated that the percentage reduction of

cooling energy in variable air volume systems (cases 7 and 8 vs case 6) were

not as prominent as in other systems.

In comparing temperature economy strategy with enthalpy economy strategy, it is

also true that the lower cooling degree day areas benefitted more from enthalpy

economy cycles than the other ciities. This may be seen from the following

table.

Table Comparing Cooling and Heating Energy Consumption Ratios of Enthalpy and

Temperature Economy Cycles

Lake

Charles Madison Nashville

Santa

Maria Seattle

Washington,

DC

Cooling

Degree Days 2739 460 1694 84 129 1415

RH with Enthalpy (Case 3)/with Temperature (Case 2), Classrooms & Offices

Cooling 0.92 0.79 0.85 0.53 0.48 0.84

Heating 1.02 1.01 1.01 1.06 1.01 1.01

VA with Enthalpy (Case 8)/with Temperature (Case 7), Classrooms & Offices

Cooling 0.96 0.86 0.93 0.61 0.57 0.91

Heating 1.01 1.00 1.00 1.03 1.01 1.00

RH = reheat

VA = variable air volume

B. Supply Air Temperature Reset

The following table compares the energy consumption results of the temperature

reset cases.

10
Table Showing Cooling and Heating Energy Consumption Ratios of Reset Strategies

Lake

Charles Madison Nashville

Santa

Maria Seattle

Washington

,

DC

Cooling

Degree Days 2739 460 1694 84 129 1415

Heating

Degree Days 1498 7730 3696 3053 5185 4211

RH System (Case 4)/Base RH (Case 1), Classrooms & Offices

Cooling 0.79 0.63 0.73 0.68 0.63 0.69

Heating 0.56 0.80 0.66 0.58 0.71 0.71

RH System with Enthalpy Economy Cycle (Case 5)/Base RH (Case 1),

Classrooms & Offices

Cooling 0.67 0.35 0.50 0.22 0.12 0.43

Heating 0.55 0.82 0.69 0.63 0.73 0.73

VA System (Case 9)/Base VA (Case 6), Classrooms & Offices

Cooling 0.94 0.88 0.91 0.72 0.70 0.89

Heating 0.69 1.01 0.92 0.44 0.97 0.97

VA System with Enthalpy Economy Cycle (Case 10)/Base VA (Case 6) > Classrooms & Offices

Cooling 0.87 0.66 0.79 0.31 0.25 0.74

Heating 0.69 1.01 0.92 0.46 0.97 0.97

DD System with Enthalpy Economy Cycle and Hot Air Reset (Case 13)/DD

System with Enthalpy Economy Cycle (Case 12), Classrooms & Offices

Cooling 0.77 0.65 0.75 0.51 0.60 0.71

Heating 0.52 0.91 0.92 0.72 0.92 0.84

DD System Hot & Cold Air Reset (Case 14)/Base DD (Case 11), Classrooms

& Offices

Cooling 0.72 0.57 0.66 0.53 0.55 0.62

Heating 0.23 0.77 0.53 0.29 0.57 0.63

RH = reheat

VA = variable air volume

DD = dual-duct

Cases 4 and 9 were single strategy cases for reheat and variable air systems

respectively. The supply air temperature was reset by the thermal zones of the

highest cooling demand. Case 14 was for dual-duct system. The cold air temperature was reset by cooling demand and the hot air was reset by the outside air

temperature. In comparing these three cases with their corresponding base systems (cases 1, 6, and 11), the cities having lower cooling degree days also had more cooling energy reduction (in percentages) than the cities having higher

degree days. This reflected the skewed temperature distribution pattern which

showed more hours in the higher temperature ranges for the high cooling degree

day areas of this study. When the reset strategy was combined with the economy

11
cycles (cases 5, 10, and 13), more energy reduction was achieved. In every

case the percentage reduction in heating energy was less in areas of higher

heating degree days.

C. Unit Ventilation Systems

Unit ventilators have long been used in schools. The flexibility of both

individual room temperature control and damper operation make them suitable for

classroom use. The unit ventilator simulated in this study had wall thermostats

for temperature modulation. Therefore, the spaces had no humidity control.

The table below compares the yearly energy consumption of unit ventilator system

with the other systems. The reheat (case 5) and variable air volume (case 10)

had both enthalpy economy cycles and supply air temperature reset. The dualduct system (case 14) had hot and cold air temperature only. The unit ventilators saved more cooling energy than the dual-duct systems in all six cities.

They wasted more cooling than the variable air volume cases. When compared

with the reheat system, the unit ventilators saved energy in low cooling degree

days cities and wasted energy in other cities. The constant air flow rate

during partial cooling period caused the unit ventilators to use more cooling

energy than the variable air volume systems. The biggest savings of the unit

ventilators were for heating. It was obvious that the high internal load of

classrooms required little heating and the unit ventilators matched the heating

load well.

Table Comparing Cooling and Heating Energy Ratios of RH, VA, DD , and UV Systems

Lake

Charles Madison

Santa

Nashville Maria Seattle

Washington,

DC

Cooling

Degree Days 2739 460 1694 84 129 1415

Heating

Degree Days 1498 7730 3696 3053 5185 4211

RH vs UV (C ase 5/Case 15), Classrooms & Offices

Cooling 1.11 1.00 1.03 0.79 0.66 1.03

Heating * 4.25 * * * *

VA vs UV (C ase 10/Case 15), Classrooms & Offices

Cooling 0.88 0.68 0.81 0.40 0.38 0.78

Heating * 3.21 * * * *

DD vs UV (C ase 14/Case 15), Classrooms & Offices

Cooling 1.05 1.34 1.17 1.58 2.48 1.26

Heating * 3.54 • * * * *

* more than 5.

RH = reheat

VA = variable air volume

DD = dual-duct

UV = unit ventilator

12
D. Fan Energy Consumption

The fan energy consumption ratios of some selected cases are listed in the

following table for comparison. A base value of 1 is used for the reheat case. When the supply air temperature was reset in the variable air volume system,

the fans consumed between 1 percent and 9 percent higher than without reset

(based on reheat system consumption). The dual-duct system had 9 percent to 13

percent more than the reheat system. This was caused by the added 0.5 in. of

water (1.2 x lO^Pa) pressure for the mixing boxes. Obviously, the best systems

were variable air volume and unit ventilator systems. It should be noted here

that the fan energy consumption of the simulations were based on a set of

assumed pressure requirements which were given in section 2.2.

Table Showing Fan Energy Consumption Ratios As Compared to RH System

Lake

Charles Madison Nashville

Santa

Maria Seattle

Washington,

DC

RH (Case 5) 1.00 1.00 1.00 1.00 1.00 1.00

VA, No Temp. Reset (C

0.61

ase 8)

0.54 0.57 0.54 0.55 0.56

VA, with Temp . Reset

0.70

(Case 10)

0.56 0.63 0.55 0.56 0.60

DD (Case 14) 1.12 1.11 1.10 1.13 1.09 1.10

UV (Case 15) 0.62 0.43 0.50 0.63 0.44 0.45

RH = reheat DD = dual-duct

VA = variable air volume UV = unit ventilator

E. System Operation Schedule

The air handling system operating schedules of all the simulations, except case

16, were based on space occupancy schedules. The system operating schedules

were given in paragraph Q of section 2.2. Case 16 had all air handling systems

operated 10 hours a day regardless of the occupancy schedule. The following

table shows the annual cooling, heating, and fan energy consumption ratios of

10 hour operation to individual scheduled operations (case 16 vs case 17).

Both cases were for the entire school operated under the same systems and

control strategies.

13
Table Showing Energy Consumption Ratios of 16 hour/day to 10 hour/day Operation

Lake

Charles Madison Nashville

Santa

Maria Seattle

Washington,

DC

Cooling

Degree Days 2739 460 1694 84 129 1415

Heating

Degree Days 1498 7730 3696 3053 5185 4211

Cooling 1.35 1.28 1.33 1.31 1.29 1.31

Heating 2.14 1.12 1.40 1.48 1.29 1.27

Fan 1.43 1.14 1.28 1.39 1.31 1.21

14
4. SUMMARY AND CONCLUSIONS

The comparative energy consumption of different air-handling systems was simulated for a large elementary school 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 unit ventilator systems. The control strategies studied included

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

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

combination of these strategies. Comparisons were also made for air-handling

system operating schedules.

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 8 through 38 depict these results correlated with cooling and heating

degree days.

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

school building, based on the parameters used in the study.

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

cycle saved more than the temperature economy cycle. Generally, more savings in percentages predicted for the cities having lower cooling degree

days. See paragraph A of section 3.2 for comparative values of these

savings

.

B. For most cities studied, the classrooms and offices had less than 3 percent

heating energy increase when economy cycles were applied to reheat and variable air volume systems. Therefore, economy cycles were particularly

suitable for school buildings with these types of air handling systems.

Dual-duct systems for the classrooms and offices had higher heating energy

consumption ranging between 10 and 27 percent when compared with systems

without enthalpy economy cycle.

C. Resetting of cold and hot supply air temperature reduced air handling

system energy consumption considerably. The energy reduction data are given in paragraph B of section 3.2. The cities of lower cooling degree

days benefitted more in cooling energy reduction than higher degree day

cities. The heating energy reduction in higher heating degree day areas were not as prominent as in lower heating degree day cities.

D. The energy consumptions of the variable air volume and unit ventilator

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 changing building loads. The heating energy savings of unit ventilators were especially large. In most cities the unit

ventilators consumed less than one-fifth of the heating energy of the other

systems. The variable air volume systems performed better than the unit

15
ventilators in cooling energy consumption. Comparison data may be seen in

paragraph C of section 3.2.

E. Substantial air transportation energy savings were obtained when variable

air volume and unit ventilator systems were used. Dual-duct systems used

more energy for transporting air than the other systems compared in this

study, because of the added pressure requirements of the mixing boxes. The

numerical comparisons are shown in paragraph D of section 3.2.

F. The difference in operating hours of the air handling systems resulted in

substantial difference in energy consumption. The cooling, heating, and

fan energy consumption ratios (10 hours a day operation vs operation according to occupancy schedules) of the entire school, with the classrooms and

offices under base reheat, were 28 to 35 percent, 12 to 48 percent, and 14

to 43 percent, respectively. Detailed ratios may be found in paragraph E

of section 3.2.

It should be mentioned again that the energy consumption predictions presented

in this study were based on assumptions for a particular school 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.

16
5. 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] Kao, J.Y., Strategies for Energy Conservation for a Large Office Building,

U.S. National Bureau of Standards, NBSIR 83-2746, July 1983.

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

Meteorological Observations, National Climatic Center, Ashville, NC,

August 1978.

[6] 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

Cooling Energy

Btu x 10^ Heating EnergyBtu x 10^

Fan Energy

Btu x 10"

For

1

Classrooms and Offices (C&0):

Base RH 1.682 0.671 0.190

2. Base RH + temperature economy 1.549 0.683 0.190

3 Base RH + enthalpy economy 1.422 0.694 0.190

4 Base RH + supply air reset by zone cooling demand 1.331 0.379 0.190

5 Base RH + enthalpy economy + supply

air reset by zone cooling demand 1.129 0.396 0.190

6 Base VA 1.023 0.080 0.117

7 Base VA + temperature economy 0.998 0.081 0.117

8 Base VA + enthalpy economy 0.960 0.082 0.117

9 Base VA + supply air reset by zone cooling demand 0.959 0.055 0.134

10 Base VA + enthalpy economy + supply

air reset by zone cooling demand 0.892 0.055 0.133

11 Base DD 1.490 0.496 0.212

12 Base DD + enthalpy economy 1.275 0.571 0.212

13 Base DD + enthalpy economy + hot

air reset 0.979 0.299 0.212

14 Base DD + hot & cold air reset 1.068 0.113 0.211

15 UV 1.019 0.001 0.118

For

16

Entire School

C/0—Case 1, Non-C/0—base* 2.523 1.501 0.331

17 C/0—Case 1, Non-C/0—base 1.874 0.701 0.232

18 C/0—Case 3, Non-C/0—base 4- enthalpy

economy 1.608 0.724 0.232

19 C/0—Case 5, Non-C/0—base 4 enthalpy

economy 1.315 0.426 0.232

20 C/ 0—Case 6 , Non-C/ 0—base 1.215 0.110 0.159

21 C/O—Case 8, Non-C/0—base 4 enthalpy

economy 1.145 0.111 0.159

22 C/0—Case 5, Non-C/0—base 4 enthalpy

economy 1.078 0.085 0.175

23 C/0—Case 11, Non—C/0—base 1.683 0.526 0.254

24 C/0—Case 13, Non-C/0—base + enthalpy

economy 1.164 0.328 0.254

25 C/0—Case 14, Non-C/O—base 4 enthalpy

economy 1.254 0.143 0.254

26 C/O—Case 15, Non-C/ 0—base 4 enthalpy

economy 1.205 0.031 0.160

* Air handling systems operating 10 hours a day.

C/0 = classroom/office areas Non-C/0 = Non-classroom/office areas —auditorium, cafeteria, kitchen, and gymnasium

RH * reheat VA *= variable air volume

DD = dual-duct

UV * unit ventilator

18
Table 2. Annual Energy Consumption - Madison, WI

Case Strategy

Cooling Energy

Btu x 10^ Heating Energy

Btu x 10^ Fan Energy

Btu x lo”

For Classrooms and Offices (C&O):

1 Base RH 0.982 1.711 0.392

2. Base RH + temperature economy 0.663 1.739 0.392

3 Base RH + enthalpy economy 0.522 1.752 0.392

4 Base RH + supply air reset by zone cooling demand 0.620 1.373 0.392

5 Base RH + enthalpy economy + supply

air reset by zone cooling demand 0.343 1.397 0.392

6 Base VA 0.354 1.042 0.211

7 Base VA + temperature economy 0.329 1.043 0.211

8 Base VA + enthalpy economy 0.283 1.044 0.211

9 Base VA + supply air reset by zone cooling demand 0.312 1.057 0.220

10 Base VA + enthalpy economy + supply

air reset by zone cooling demand 0.235 1.057 0.219

11 Base DD 0.812 1.506 0.436

12 Base DD + enthalpy economy 0.451 1.660 0.436

13 Base DD + enthalpy economy + hot

air reset 0.295 1.504 0.436

14 Base DD + hot & cold air reset 0.460 1.164 0.436

15 UV 0.344 0.329 0.170

For Entire School

16 C/O—Case 1, AUS —base* 1.320 2.715 0.569

17 C/0—Case 1, Non-C/0—base 1.029 2.424 0.501

18 C/O—Case 3, Non-C/0—base + enthalpy

economy 0.563 2.465 0.501

19 C/0—Case 5, Non-C/O—base + enthalpy

economy 0.383 2.111 0.501

20 C/O—Case 6, Non-C/0—base 0.402 1.756 0.321

21 C/O—Case 8, Non-C/0—base + enthalpy

economy 0.324 1.757 0.321

22 C/0—Case 5, Non-C/0—base + enthalpy

economy 0.276 1.770 0.329

23 C/0—Case 11, Non-C/0—base 0.859 2.219 0.546

24 C/0—Case 13, Non-C/0—base + enthalpy

economy 0.336 2.217 0.546

25 C/0—Case 14, Non-C/0—base + enthalpy

economy 0.501 1.877 0.546

26 C/0—Case 15, Non-C/0—base + enthalpy

economy 0.385 1.043 0.280

* Air handling systems operating 10 hours a day.

C/0 = classroom/office areas

Non1-C/O = Non-classroom/office areas —auditorium, cafeteria, kitchen, and gymnasium

RH = reheat

VA = variable air volume

DD = dual-duct

UV '= unit ventilator

19
Table 3. Annual Energy Consumption - Nashville, TN

Case Strategy

Cooling Energy Heating Energy Fan Energy

Btu x 10^ Btu x 10^ Btu x lo"

For Classrooms and Offices (C&0)

1 Base RH 1.366 0.977 0.260

2. Base RH + temperature economy 1.096 1.001 0.260

3 Base RH + enthalpy economy 0.937 1.015 0.260

4 Base RH + supply air reset by zone cooling demand 0.992 0.644 0.260

5 Base RH + enthalpy economy + supply

air reset by zone cooling demand 0.687 0.671 0.260

6 Base VA 0.683 0.319 0.149

7 Base VA + temperature economy 0.646 0.320 0.149

8 Base VA + enthalpy economy 0.601 0.321 0.149

9 Base VA + supply air reset by zone cooling demand 0.621 0.295 0.164

10 Base VA + enthalpy economy + supply

air reset by zone cooling demand 0.540 0.295 0.164

11 Base DD 1.178 0.787 0.287

12 Base DD + enthalpy economy 0.831 0.923 0.287

13 Base DD + enthalpy economy + hot air reset 0.622 0.727 0.287

14 Base DD + hot & cold air reset 0.775 0.418 0.287

15 UV 0.664 0.055 0.130

For Entire School

16 C/0—Case 1, Non-C/0—base* 1.963 1.592 0.416

17 C/ 0—Case 1 , Non-C/ 0—base 1.480 1.139 0.324

18 C/0—Case 3, Non-C/0—base + enthalpy

economy 1.045 1.177 0.324

19 C/0—Case 5, Non-C/0—base + enthalpy

economy 0.795 0.833 0.324

20 C/0—Case 6, Non—C/0—base 0.797 0.481 0.214

21 C/0—Case 8, Non-C/O—base + enthalpy

economy 0.709 0.483 0.214

22 C/0—Case 5, Non-C/0—base + enthalpy economy 0.648 0.457 0.228

23 C/0—Case 11, Non-C/0—base 1.293 0.949 0.352

24 C/0—Case 13, Non-C/O— base + enthalpy

economy 0.730 0.889 0.352

25 C/0—Case 14, Non-C/0—base + enthalpy economy 0.883 0.580 0.352

26 C/0—Case 15, Non-C/0—base + enthalpy economy 0.772 0.217 0.194

* Air handling systems operating 10 hours a day.

C/O = classroom/off ice areas

Non -C/0 = Non-classroom/office areas —auditorium, cafeteria, kitchen. and gymnasium

RH - reheat VA *= variable air volume

DD “ dual-duct

UV >= unit ventilator

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

Cooling Energy

Btu x 10^ Heating Energy Fan Energy

Case Strategy Btu x 10^ Btu x 10^

For Classrooms and Offices (C&0):

1 Base RH 1.166 0.856 0.168

2. Base RH + temperature economy 1.014 0.870 0.168

3 Base RH + enthalpy economy 0.541 0.912 0.168

4 Base RH + supply air reset by zone cooling demand 0.792 0.493 0.166

5 Base RH + enthalpy economy + supply

air reset by zone cooling demand 0.258 0.539 0.168

6 Base VA 0.422 0.146 0.090

7 Base VA + temperature economy 0.388 0.147 0.090

8 Base VA + enthalpy economy 0.235 0.151 0.090

9 Base VA + supply air reset by zone cooling demand 0.305 0.064 0.094

10 Base VA + enthalpy economy + supply

air reset by zone cooling demand 0.131 0.067 0.093

11 Base DD 0.964 0.644 0.189

12 Base DD + enthalpy economy 0.448 0.817 0.189

13 Base DD + enthalpy economy + hot

air reset 0.230 0.591 0.189

14 Base DD + hot & cold air reset 0.514 0.188 0.189

15 UV 0.325 0.007 0.106

For Entire School

16 C/0—Case 1, Non-C/0—base* 1.560 1.325 0.273

17 C/0—Case 1, Non-C/0—base 1.192 0.897 0.196

18 C/O—Case 3, Non-C/0—base + enthalpy

economy 0.560 0.952 0.196

19 C/0—Case 5, Non-C/0—base + enthalpy

economy 0.276 0.580 0.196

20 C/0—Case 6, Non-C/0—base 0.448 0.187 0.118

21 C/0—Case 8, Non-C/O—base + enthalpy

economy 0.253 0.191 0.118

22 C/0—Case 5, Non-C/0—base + enthalpy

economy 0.149 0.107 0.121

23 C/0—Case 11, Non-C/0—base 0.990 0.684 0.217

24 C/0—Case 13, Non-C/0—base + enthalpy

economy 0.248 0.631 0.217

25 C/0—Case 14, Non-C/O—base + enthalpy

economy 0.533 0.228 0.217

26 C/0—Case 15, Non-C/0—base + enthalpy

economy 0.343 0.047 0.135

* Air handling systems operating 10 hours a day.

C/0 = classroom/of f ice areas Non-C/0 = Non-classroom/of f ice areas —auditorium, cafeteria, kitchen, and gymnasium

RH = reheat VA = variable air volume

DD “ dual-duct

UV = unit ventilator

21
Table 5. Annual Energy Consumption - Seattle, WA

Case Strategy

Cooling Energy

Btu x 10 9 Heating EnergyBtu x 10 9 Fan Energy

Btu x 109

For

i

Classrooms and Offices (C&0):

Ease RH 0.963 1.191 0.291

2. Base RE + temperature economy 0.497 1.220 0.291

3 Base RE + enthalpy economy 0.241 1.232 0.291

4 Base RE + supply air reset by tone cooling demand 0.603 0.846 0.291

5 Base RE + enthalpy economy + supply

air reset by zone cooling demand .0.116 0.873 0.291

6 Base VA 0.266 0.529 0.160

7 Base VA + temperature economy 0.192 0.531 0.160

8 Base VA + enthalpy economy 0.109 0.531 0.160

9 Base VA + supply air reset by zone cooling demand 0.185 0.513 0.164

10 Base VA + enthalpy economy + supply

air reset by zone cooling demand 0.067 0.514 0.164

11 Base DD 0.785 0.995 0.316

12 Base DD + enthalpy economy 0.206 1.144 0.316

13 Base DD + enthalpy economy + hot

air reset 0.124 1.504 0.316

14 Base DD + hot & cold air reset 0.434 0.571 0.316

15 UV 0.175 0.059 0.127

For

16

Entire School

C/0—Case 1, Non—C/O—base* 1.264 1.662 0.419

17 C/ 0—Case 1 , Non—C/ 0—base 0.980 1.290 0.319

18 C/0—Case 3, Non-C/O—base + enthalpy

economy 0.252 1.354 0.319

19 C/0—Case 5, Non-C/O—base + enthalpy economy 0.127 0.981 0.319

20 C/0-—Case 6, Non—C/0—-base 0.277 0.539 0.188

21 C/ 0—Case 8, Non-C/O—base + enthalpy

economy 0.120 0.543 0.188

22 C/0—Case 5, Non-C/O—base + enthalpy

economy 0.077 0.501 0.192

23 C/ 0—Case 11, Non-C/O—base 0.802 1.084 0.344

24 C/0—Case 13, Non-C/O—base + enthalpy

economy 0.134 1.205 0.344

25 C/0—Case 14, Non-C/O—base + enthalpy

economy 0.445 0.722 0.344

26 C/0—Case 15, Non-C/O—base + enthalpy

economy 0.186 0.209 0.155

* Air handling systems operating 10 hours a day.

C/0 = classroom/office areas Son-C/0 = Non-classroom/of f ice areas —auditorium, cafeteria, kitchen, and gymnasium

RE = reheat VA = variable air volume

DD = dual-duct

UV « unit ventilator

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

Cooling Energy Heating Energy Fan Eneri Case Strategy Btu x 10 9 Btu x 10 9 Btu x 10

For Classrooms and Offices (C&0):

i Base RH 1.221 1.191 0.319

2. Base RH + temperature economy 0.893 1.220 0.319

3 Base RH + enthalpy economy 0.749 1.232 0.319

4 Base RH + supply air reset by zone cooling demand 0.842 0.846 0.319

5 Base RH + enthalpy economy + supply

air reset by zone cooling demand 0.529 0.873 0.319

6 Base VA 0.544 0.529 0.178

7 Base VA + temperature economy 0.500 0.531 0.178

8 Base VA + enthalpy economy 0.456 0.531 0.178

9 Base VA + supply air reset by zone cooling demand 0.486 0.513 0.191

10 Base VA + enthalpy economy + supply

air reset by zone cooling demand 0.404 0.514 0.190

11 Base DD 1.039 0.995 0.352

12 Base DD + enthalpy economy 0.658 1.144 0.352

13 Base DD + enthalpy economy + hot

air reset 0.470 0.965 0.352

14 Base DD + hot & cold air reset 0.649 0.630 0.352

15 UV 0.515 0.123 0.142

For Entire School

16 C/0—-Case 1, Non—C/O—base* 1.712 1.902 0.490

17 C/O—Case 1, Non—C/0—base 1.306 1.496 0.405

18 C/0—Case 3, Non-C/0—base + enthalpy

economy 0.827 1.538 0.405

19 C/0—Case 5, Non-C/0—base + enthalpy

economy 0.607 1.179 0.405

20 C/ 0—Case 6, Non—C/O—base 0.622 0.835 0.263

21 C/0—Case 8, Non-C/O—base + enthalpy

economy 0.534 0.837 0.263

22 C/0—Case 5, Non-C/0—base + enthalpy

economy 0.483 0.819 0.276

23 C/0—Case 11, Non—C/0—base 1.123 1.301 0.438

24 C/0—Case 13, Non-C/0—base + enthalpy

economy 0.548 1.270 0.438

25 C/0—Case 14, Non-C/0—base + enthalpy

economy 0.727 0.935 0.438

26 C/0—Case 15, Non-C/O—base + enthalpy

economy 0.593 0.428 0.228

* Air handling systems operating 10 hours a day.

C/0 = classroom/off ice areas Non-C/0 = Non-classroom/office areas—auditorium, cafeteria, kitchen, and gymnasium

RH *= reheat VA = variable air volume

DD dual-duct

UV * unit ventilator

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

Cooling Energy Keating Energy Fan Energy Consumption, lO-’ Btu/ft^

Case Strategy Ratio-Relative to Case 1

For Classroom and Offices (C&O)

1 Base RH 37,99 15.16 4.28

1.00 1.00 1.00

2 Base RH + temperature economy 34.99 15.43 4.28

0.92 1.02 1.00

3 Base RH + enthalpy economy 32.12 15.68 4.28

0.8S 1.03 1.00

4 Base RH + supply air reset by 30.07 8.56 4.28

zone cooling demand 0.79 0.56 1.00

5 Base RH + enthalpy economy + supply 25.50 8.95 4.28

air reset by zone cooling demand 0.67 0.59 1.00

6 Base VA 23.11 1.80 2.63

0.61 0.12 0.62

7 Base VA + temperature economy 22.54 1.82 2.63

0.59 0.12 0.62

8 Base VA + enthalpy economy 21.69 1.84 2.63

0.57 0.12 0.62

9 Base VA + supply air reset by 21.66 1.24 3.02

zone cooling demand 0.57 0.08 0.70

10 Base VA + enthalpy economy + supply 20.15 1.24 3.00

air reset by zone cooling demand 0.53 0.08 0.70 n Base DD 33.66 11.20 4.79

0.89 0.74 1.12

12 Base DD + enthalpy economy 28.80 12.90 4.79

0.76 0.85 1.12

13 Base DD + enthalpy economy + hot 22.11 6.75 4.79

air reset 0.58 0.45 1.12

14 Base DD + hot & cold air reset 24.13 2.55 4.79

0.63 0.17 1.12

15 UV 23.02 0.03 2.67

0.61 0.002 0.62

For Entire School

16 CO—Case 1, Non-C/O— base* 42.56 25.32 5.58

1.35 2.14 1.43

17 CO—Case 1, Non-C/O— base 31.61 11.82 3.91

1.00 1.00 1.00

18 CO—Case 3, Non-C/0—base + enthalpy 27.12 12.21 3.91 economy 0.86 1.03 1.00

19 C/O—Case 5, Non-C/0—base + enthalpy 22.18 7.19 3.91 economy 0.70 0.61 1.00

20 C/0—Case 6, Non-C/O— base 20.49 1.86 2.68 0.65 0.16 0.69

21 C/O—Case 8, Non-C/O— base + enthalpy 19.31 1.87 2.68 economy 0.61 0.16 0.69

22 C/0—Case 3, Non-C/O— base + enthalpy 18. 18 1.43 2.95 economy 0.58 0.12 0.75

23 C/ 0—Case 11, Non-C/0—base 28.39 8.87 4.28

0.90 0.75 1.09

24 C/0—Case 13, Non-C/O— base + enthalpy 19.63 5.53 4.28 economy 0.62 0.47 1.09

25 C/0—Case 14, Non-C/0—base + enthalpy 21.15 2.41 4.28 economy 0.67 0.20 1.09

26 C/O—Case 15, Non-C/O— base + enthalpy 20.33 0.52 2.70 economy 0.64 0.04 0.69

* Air handling systems on 10 hours a day.

C/O - classroom/office areas

Non--C/0 * Non-classroom/of flee areas —auditorium, cafeteria, kitchen. and gymnasium

RH = reheat DD dual-duct

VA > variable air volume UV - unit ventilator

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

Cooling Energy Heating Energy Fan Energy Consumption, 10^ Btu/ft^

Case Strategy Ratio-Relative to Case 1

For Classroom and Offices (C&O)

:

1 Base RH 22.18 38.65 8.85

1.00 1.00 1.00

2 Base RH + temperature economy 14.98 39.28 8.85

0.68 1.02 1.00

3 Base RH + enthalpy economy 11.79 39.58 8.85

0.53 1.02 1.00

4 Base RH + supply air reset by 14.01 31.01 8.85

zone cooling demand 0.63 0.80 1.00

5 Base RH + enthalpy economy + supply 7.75 31.56 8.85

air reset by zone cooling demand 0.35 0.82 1.00

6 Base VA 7.80 23.54 4.77

0.36 0.82 0.54

7 Base VA + temperature economy 7.80 23.54 4.77

0.36 0.61 0.54

8 Base VA + enthalpy economy 7.43 23.56 4.77

0.33 0.61 0.54

9 Base VA + supply air reset by 6.39 23.58 4.97

zone cooling demand 0.29 0.62 0.56

10 Base VA + enthalpy economy + supply 5.31 23.88 4.95

air reset by zone cooling demand 0.24 0.62 0.56

11 Base DO 18.34 34.02 9.85

0.83 0.88 1.11

12 Base DD + enthalpy economy 10.19 37.50 9.85

0.46 0.97 1.11

13 Base DD + enthalpy economy + hot 6.66 33.97 9.85

air reset 0.30 0.88 1.11

14 Base DD + hot & cold air reset 10.39 26.29 9.85

0.47 0.68 1.11

15 UV 7.77 7.43 3.84

0.35 0.19 0.43

For Entire School

16 C/0—case 1, Non-C/0—base* 22.27 45.80 9.60

1.28 1.12 1.14

17 C/0—case 1, Non-C/0—base 17.36 40.89 8.45

1.00 1.00 1.00

18 C/0—case 3, Non-C/0—base + enthalpy 9.50 41.58 8.45 economy 0.55 1.02 1.00

19 C/0—Case 5, Non-C/0—base + enthalpy 6.46 35.61 8.45 economy 0.37 0.87 1.00

20 C/ 0—-Case 6, Non—C/0——base 6.78 29.62 5.41 0.39 0.72 0.64

21 C/0—Case 8, Non-C/0—base + enthalpy 5.47 29.64 5.41 economy 0.31 0.72 0.64

22 C/0—Case 5, Non-C/0—base + enthalpy 4.66 29.86 5.55 economy 0.27 0.73 0.66

23 C/0—Case 11, Non-C/0—base 14.49 37.43 9.21 0.83 0.92 1.09

24 C/0—Case 13, Non-C/O—base + enthalpy 5.67 37.40 9.21 economy 0.33 0.91 1.09

25 C/0—Case 14, Non-C/0—base + enthalpy 8.45 31.66 9.21 economy 0.49 0.77 1.09

26 C/0—Case 15, Non-C/0—base + enthalpy 6.49 17.59 4.72 economy 0.37 0.43 0.56

* Air handling systems on 10 hours a day.

C/0 * classroom/office areas Non-C/0 Non-classroom/of f ice areas—auditorium, cafeteria, kitchen, and gymnasium

RH * reheat DD dual-duct

VA * variable air volume UV * unit ventilator

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

Cooling Energy Heating Energy Fan Energy Consumption, 10^ Btu/ft^

Case Strategy Ratio-Relative to Case 1

For Classroom and Offices (C&O):

1 Base RH 30.86 22.07 5.87 1.00 1.00 1.00

2 Base RH + temperature economy 24.76 22.61 5.87 0.80 1.02 1.00

3 Base RH + enthalpy economy 21.17 22.93 5.87 0.69 1.04 1.00

4 Base RH + supply air reset by 22.41 14.55 5.87 zone cooling demand 0.73 0.66 1.00

3 Base RH + enthalpy economy + supply 15.52 15.16 5.87

air reset by zone cooling demand 0.50 0.69 1.00

6 Base VA 15.43 7.21 3.37 0.50 0.33 0.57

7 Base VA + temperature economy 14.59 7.23 3.37

0.47 _0. 33 0.57

8 Base VA + enthalpy economy 13.58 7.25 3.37 0.44 0.33 0.57

9 Base VA + supply air reset by 14.03 6.66 3.70

zone cooling demand 0.45 0.30 0.63

10 Base VA + enthalpy economy + supply 12.20 6.66 3.70

air reset by zone cooling demand 0.40 0.30 0.63

11 Base DD 26.61 17.78 6.48

0.86 0.81 1.10

12 Base DD + enthalpy economy 18.77 20.85 6.48

0.61 0.94 1.10

13 Base DD + enthalpy economy + hot 14.05 16.42 6.48

air reset 0.46 0.74 1.10

14 Base DD + hot & cold air reset 17.51 9.44 6.48

0.57 0.43 1.10

15 UV 15.00 1.24 2.94

0.49 0.06 0.50

For Entire School

16 C/0—Case 1, Non-C/0—base* 33.11 26.85 7.02

1.33 1.40 1.28

17 C/ 0—Case 1, Non-C/0—base 24.96 19.21 5.47

1.00 1.00 1.00

18 C/0—Case 3, Non-C/O— base + enthalpy 17.63 19.85 5.47 economy 0.71 1.03 1.00

19 C/0—Case 5, Non-C/0—base + enthalpy 13.41 14.05 5.47 economy 0.54 0.73 1.00

20 C/ 0—Case 6, Non—C/0—base 13.44 8.11 3.61 0.54 0.42 0.66

21 C/0—Case 8, Non-C/0—base + enthalpy 11.96 8.15 3.61 economy 0.48 0.42 0.66

22 C/0—Case 5, Non-C/0—base + enthalpy 10.93 7.71 3.85 economy 0.44 0.57 0.70

23 C/0—Case 11, Non-C/0—base 21.81 16.01 5.94

0.87 0.83 1.09

24 C/0—Case 13, Non-C/0—base + enthalpy 12.31 15.00 5.94 economy 0.49 0.78 1.09

25 C/0—Case 14, Non-C/O— base + enthalpy 14.89 9.78 5.94 economy 0.60 0.51 1.09

26 C/O—Case 15, Non-C/0—base + enthalpy 13.02 3.66 3.27 economy 0.52 0.19 0.60

* Air handling systems on 10 hours a day.

C/0 * classroom/office areas

Non -C/0 - Non-classroom/office areas—auditorium, cafeteria, kitchen. and gymnasium

RH =* reheat DD - dual-duct

VA - variable air volume UV unit ventilator 26
Table 10* Comparative Annual Energy Consumption - Santa Maria, CA

Cooling Energy Heating Energy Fan Energy Consumption, 10^ Btu/ft^

Case Strategy Ratio-Relative to Case 1

For Classroom and Offices (C&O)

:

1 Base RH 26.34 19.34 3.79 1.00 1.00 1.00

2 Base RH + temperature economy 22.91 19.65 3.79

0.87 1.02 1.00

3 Base RH + enthalpy economy 12.22 20.60 3.79

0.46 1.07 1.00

4 Base RH + supply air reset by 17.89 11.14 3.79

zone cooling demand 0.68 0.58 1.00

5 Base RH + enthalpy economy + supply 5.83 12.18 3.79

air reset by zone cooling demand 0.22 0.63 1.00

6 Base VA 9.53 3.30 2.03

0.36 0.17 0.54

7 Base VA + temperature economy 8.76 3.32 2.03

0.33 0.17 0.54

8 Base VA + enthalpy economy 5.31 3.41 2.03

0.20 0.18 0.54

9 Base VA + supply air reset by 6.89 1.45 2. 12 zone cooling demand 0.26 0.07 0.56

10 Base VA + enthalpy economy + supply 2.96 1.51 2.10

air reset by zone cooling demand 0.11 0.08 0.55

11 Base DD 21.78 14.55 4.27

0.83 0.75 1.13

12 Base DD + enthalpy economy 10.12 18.46 4.27

0.38 0.95 1.13

13 Base DD + enthalpy economy + hot 5.20 13.35 4.27

air reset 0.20 0.69 1.13

14 Base DD + hot & cold air reset 11.61 4.25 4.27 0.44 0.22 1.13

15 OV 7.34 0.16 2.39

0.28 0.01 0.63

For Entire School

16 C/0—Case 1, Non-C/0—base* 26.31 22.35 4.60

1.31 1.48 1.39

17 C/0—Case 1, Non-C/0—base 20.11 15.13 3.31

1.00 1.00 1.00

18 C/0—Case 3, Non-C/O—base + enthalpy 9.45 16.06 3.31 economy 0.47 1.06 1.00

19 C/0—Case 5, Non-C/0—base + enthalpy 4.66 9.78 3.31 economy 0.23 0.65 1.00

20 C/0—Case 6, Non-C/0—base 7.56 3.15 1.99 0.38 0.21 0.60

21 C/0—Case 8, Non-C/0—base + enthalpy 4.27 3.22 1.99 economy 0.21 0.21 0.60

22 C/O—Case 5, Non-C/O—base + enthalpy 2.51 1.80 2.04 economy 0.13 0.12 0.62

23 C/0—Case 11, Non-C/O—base 16.70 11.54 3.66 0.83 0.76 1.11

24 C/0—Case 13, Non-C/0—base + enthalpy 4.18 10.64 3.66 economy 0.21 0.70 1.11

25 C/0—Case 14, Non-C/0—base + enthalpy 8.99 3.85 3.66 economy 0.45 0.25 1.11

26 C/0—Case 15, Non-C/0—base + enthalpy 5.79 0.79 2.78 economy 0.29 0.05 0.69

* Air handling systems on 10 hours a day.

C/0 = classroom/office areas Non-C/0 * Non-classroom/office areas —auditorium, cafeteria, kitchen, and gymnasium

RH reheat DD dual-duct

VA variable air volume UV unit ventilator

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

Cooling Energy Heating Energy Fan Energy Consumption, 10^ Btu/ft^

Case Strategy Ratio-Relative to Case 1

For Classroom and Offices (C&0):

1 Base RH 21.75 26.90 6.57

1.00 1.00 1.00

2 Base RH + temperature economy 11.23 27.56 6.57

0.52 1.02 1.00

3 Base RH + enthalpy economy 5.44 27.83 6.57

0.25 1.03 1.00

4 Base RH + supply air reset by 13.62 19.11 6.57

zone cooling demand 0.63 0.71 1.00

5 Base RH + enthalpy economy + supply 2.62 19.72 6.57

air reset by zone cooling demand 0.12 0.73 1.00

6 Base VA 6.01 11.95 3.61 0.28 0.44 0.55

7 Base VA + temperature economy 4.37 11.99 3.61 0.20 0.45 0.55

8 Base VA + enthalpy economy 2.46 11.99 3.61 0.11 0.45 0.55

9 Base VA + supply air reset by 4.18 11.59 3.70

zone cooling demand 0.19 0.43 0.56

10 Base VA + enthalpy economy + supply 1.51 11.61 3.70

air reset by zone cooling demand 0.07 0.43 0.56

11 Base DD 17.73 22.48 7.14

0.82 0.84 1.09

12 Base DD + enthalpy economy 4.65 25.84 7.14

0.21 0.96 1.09

13 Base DD + enthalpy economy + hot 2.80 23.81 7.14

air reset 0.13 0.88 1.09

14 Base DD + hot & cold air reset 9.80 12.90 7.14

0.45 0.48 1.09

15 UV 3.95 1.33 2.87 0.18 0.05 0.44

For Entire School

16 C/ 0—Case 1 , Non-C/ 0—base* 21.32 28.03 7.07

1.29 1.29 1.31

17 C/ 0—Case 1 , Non-C/ 0—base 16.53 21.76 5.38

1.00 1.00 1.00

18 C/0—Case 3, Non-C/ 0—base + enthalpy 4.25 22.84 5.38 economy 0.26 1.05 1.00

19 C/0—Case 5, Non-C/0—base + enthalpy 2.14 16.55 5.38 economy 0.13 0.76 1.00

20 C/0—Case 6, Non-C/0—base 4.67 9.09 3.17 0.28 0.42 0.59

21 C/0—Case 8, Non-C/O—base + enthalpy 2.02 9.16 3.17 economy 0.12 0.42 0.59

22 C/0—Case 5, Non-C/0—base + enthalpy 1.30 8.45 3.24 economy 0.08 0.39 0.60

23 C/0—Case 11, Non-C/0—base 13.53 18.28 5.80

0.82 0.84 1.08

24 C/0—Case 13, Non-C/0—base + enthalpy 2.26 20.33 5.80 economy 0.14 0.93 1.08

25 C/0—Case 14, Non-C/0—base + enthalpy 7.51 12.18 5.80 economy 0.45 0.59 1.08

26 C/0—Case 13, Non-C/O—base + enthalpy 3.14 3.53 2.61 economy 0.19 0.16 0.49

* Air handling systems on 10 hours a day.

C/0 classroom/office areas

Non--C/0 Non-classroom/office areas —auditorium, cafeteria, kitchen. and gymnasium

RH - reheat DD * dual-duct

VA < variable air volume UV unit ventilator 28
Table 12. Comparative Annual Energy Consumption - Washington, DC

Cooling Energy Heating Energy Fan Energy Consumption, 10^ Btu/ft^

Case Strategy Ratio-Relative to Case 1

For Classroom and Offices (C&O):

1 Base RH 27.58 26.90 7.21 1.00 1.00 1.00

2 Base RH + temperature economy 20.17 27.56 7.21 0.73 1.02 1.00

3 Base RH + enthalpy economy 16.92 27.83 7.21

0.61 1.03 1.00

4 Base RH + supply air reset by 19.02 19.11 7.21 zone cooling demand 0.69 0.71 1.00

5 Base RH + enthalpy economy + supply 11.95 19.72 7.21 air reset by zone cooling demand 0.43 0.73 1.00

6 Base VA 12.29 11.95 4.02

0.45 0.44 0.56

7 Base VA + temperature economy 11.29 11.99 4.02

0.41 0.45 0.56

8 Base VA + enthalpy economy 10.30 11.99 4.02

0.37 0.45 0.56

9 Base VA + supply air reset by 10.98 11.59 4.31

zone cooling demand 0.40 0.43 0.60

10 Base VA + enthalpy economy + supply 44.27 11.61 4.29

air reset by zone cooling demand 0.33 0.43 0.60

11 Base DD 23.47 22.48 7.95 0.85 0.83 1.10

12 Base DD + enthalpy economy 14.86 25.84 7.95

0.54 0.96 1.10

13 Base DD + enthalpy economy + hot 10.62 21.80 7.95

air reset 0.38 0.81 1.10

14 Base DD + hot & cold air reset 14.66 14.23 7.95 0.53 0.53 1.10

15 uv 11.63 2.78 3.21 0.42 0.10 0.45

For Entire School

16 CO--Case 1, Non-C/ 0—base* 28.88 32.08 8.27

1.31 1.27 1.21

17 CO—Case 1, Non-C/0—base 22.03 25.23 6.83

1.00 1.00 1.00

18 CO—Case 3, Non-C/0—base + enthalpy 13.95 25.94 6.83 economy 0.63 1.03 1.00

19 C/0—Case 5, Non-C/0—base + enthalpy 10.24 19.89 6.83 economy 0.46 0.79 1.00

20 C/0—Case 6, Non-C/0—base 10.49 14.08 4.44 0.48 0.56 0.65

21 C/0—Case 8, Non-C/0—base + enthalpy 9.01 14.12 4.44 economy 0.41 0.56 0.65

22 C/0—Case 5, Non-C/ 0—base + enthalpy 8.15 13.81 4.66 economy 0.37 0.55 0.68

23 C/0—Case 11, Non-C/0—base 18.94 21.95 7.39

0.86 0.87 1.08

24 C/0—Case 13, Non-C/0—base + enthalpy 9.24 21.42 7.39 economy 0.42 0.85 1.08

25 C/0—Case 14, Non-C/O— base + enthalpy 12.26 15.77 7.39 economy 0.56 0.63 1.08

26 C/0—Case 15, Non-C/0—base + enthalpy 10.00 7.22 3.85 economy 0.45 0.29 0.56

* Air handling systems on 10 hours a day.

C/0 - classroom/office areas

Non -C/0 = Non-classroom/office areas —auditorium, cafeteria, kitchen. and gymnasium

W :* reheat, variable air volume

• dual-duct , unit ventilator

29
Exterior Wall:

4" (102 mm) face brick, 2" (51 mm ) rigid insulation, and

8" ( 203 mm) concrete block

Roof : built-up roof, 2" (51 mm) rigid insulation, metal deck,

air space, and 3/4" ( 19 mm) ceiling panels

Partition

8" ( 203 mm) concrete block, or

1/2" ( 13 mm) gypsum board on both sides of metal frame

Window

single pane sheet glass and light color ventilation blind

Figure 1. School building model

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4-t to X o

CO X

X

CO

(1) XXwXXQXXXX

C5z

4-t P—4 XxMX

35

Figure

6.

Cafeteria

internal

load

profiles
Fraction

of

total

Fraction

of

total

<rCM

CMCMo

CM

00

VO

00

v£>

CM

>1

M <0 3 -a O M X 0)

a) co

CAM

a)ac

a>aa

a>

vO X

cOO

CM

CMCMo

CM

00

vO

CM

00

M3

CM

CJ

(0U

[1-1

uaoX

aj XX

a)

<u 3

CM

a3

vO

OO

CM

4-1 4-1 3

oooX

COO

<r

CM

CM

CMo

CM

CO

r-l vO

Cl3OX

00

\£>

CM

>>

CO X£3X.

CO X

Cl3

4J

CO to

(0

<uCL

COXXXQXXoX

>1Xz<XXxXo

<rCM

CM

CMo

CM

CO

so

oo

M3

>,

CO Xc3

CO

-<3

>» X

Cl3

4-1 <0

•HOCT'OOr^'-OLTlMroOCMH O t-l COCl 04 *

CO

<DCL XXXXQXXXX

C3z

H-l HXX

36

Figure

7.

Gymnasium

internal

load

profiles
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10^

Btu

3 . 0

CN

2.5

2.0

CDD CITY

84 Santa Maria

129 Seattle

460 Madison

1415 Washington

1694 Nashville

2739 Lake Charlei

__ 00.0

_ _ 50 .

0

<

__ -10.0

30.0

1.0 __ 20.0

.5 -- 10 . 0

0.0 1 1 1 r-50

i 1 i—I 1 1 r r 100 150 Cooling degree days x 10

T” ’ |

I » — » I ITT

200 250

-l

0.0

300

Figure 8. Cooling and heating energy consumption of case 1 (classrooms and offices) — base reheat

37

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10 J

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

HT

Btu

3 . 0

COD CITY __ 00.0

2.5 - 84 Santa Marla

129 Seattle

460 Madison

2.0 - " 1415 Washington

• 1694 Nashville

2739 Lake Charle

1 .!

1.0 —

o

0.0

50 100 150

(N

__ 50.0 <

- - -40.0

-- 30.0

30 . 0

10.0

200

-i 1 * i

| 250

I I i r- 0.0

300 Cooling degree days x 10

-1

60 . 0

50.0

40.

0

30.0

20.0

10.0

0.0

Heating degree days x 10

Figure 9. Cooling and heating energy consumption of case 2 (classrooms and offices) — base reheat with temperature

economy cycle

38

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10 J

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10*

Btu

3.0

(N

Heating degree days x 10

Figure 10. Cooling and heating energy consumption of case 3 (classrooms and offices) — base reheat with enthalpy

economy cycle

39

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10 J

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

Heating degree days x 10

Figure 11. Cooling and heating energy consumption of case 4

(classrooms and offices) — base reheat with supply air

temperature reset by zone load demand

40

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

60 . 0 D

4-J PQ 50.0 **'

40.0

30.0

uiu

0)c

0)00c

20.0

10.0 M

03

tt) >< 0.0

>»

00

(Uc

0)00c

03

0) X

rH

0)

0) tn

Heating degree days x 10

Figure 12. Cooling and heating energy consumption of case 5 (classrooms and offices) — base reheat with enthalpy

economy and supply air temperature reset by zone load

demand

41
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

3.0

CDD CITY

2.5 - 64 Santa Maria

129 Seattle

' 460 Madison

2.0 - - 1415 Washington

1694 Nashville

2739 Lake Charle

CN REHEAT

Case 1 —base RH Case 2 —temperature economy

Case 3—enthalpy economy

Case 4 —zone reset Case 5 —enthalpy economy +

zone reset

__ o0.e

50 . e t

-- -»o.«

30. e

JO. 0

10 . 0

0.0

200 250

Cooling degree days x 10

^

60 . 0

50 . 0

40.

0

30.0

20.0

10.0

0.0

Figure 13. Cooling and heating energy consumption of cases 1 through 5 (classrooms and offices) — all reheat cases

42

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

Figure 14. Cooling and heating energy consumption of case 6

(classrooms and offices) — base variable air volume

43

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

Heating degree days x 10

Figure 15. Cooling and heating energy consumption of case 7 (classrooms and offices) — base variable air volume with

temperature economy cycle

44

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

3.0

o0. e 2.5

2.0

CDD CITY

84 Santa Maria

129 Seattle

460 Madison

1415 Washington

1694 Nashville

2739 Lake Charle

i

-- 50.0

{SI

r

-- -10.0

30.0

1G0 150 Cooling degree days x 10

20. 0

10.0

0.0

60. 0

50. 0

40. u

30.0

20. 0

10.0

0.0

heating degree days x 10

Figure 16. Cooling and heating energy consumption of case 8

(classrooms and offices) —1 base variable air volume with

enthalpy economy cycle

45

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10*

Btu

Heating degree days x 10

Figure 17. Cooling and heating energy consumption of case 9

(classrooms and offices) — base variable air volume with

supply air temperature reset by zone load demand

46

Yearly

heating

energy,

10

Btu/ft

Yearly

coollng

energy>

10 3

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

Figure 18. Cooling and heating energy consumption of case 10

(classrooms and offices) — base variable air volume with

enthalpy economy cycle and supply air temperature reset by zone load demand

Yearly

heating

energy,

10

Btu/fc

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10^

Btu

Yearly

cooling

energy,

10

Bt

3.0

1.5

1.0

CDD CITY

2.5 - 84 Santa Maria

129 Seattle

460 Mad 1 8 on

2.0 1 - 1415 Washington

1694 Nashville

2739 Lake Charlei

VARIABLE AIR VOLUME

Case 6—base VAV

Case 7 —temperature economy

Case 8—enthalpy economy

Case 9 —zone reset Case 10—enthalpy economy +

zone reset

150 200 250

Cooling degree days x 10 1

-- 60 . e 3

4J a

--50 .0 '"’l

40.0

3O.0

-- 20.0

10.0

0.0

300

>>

00L

0)c

oi00c

Li

oi

tN

3«

>

00

Li

0)c

QJ00a

•H

to

01 JC

Li

tO

01 <

Figure 19- Cooling and heating energy consumption of cases 6 through 10

(classrooms and offices) — all variable air volume cases

48
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10*

Btu

3.0

60.0

CDD CITY

•

84 Santa Maria

129 Seattle * 460 Madison -- 1415 Washington - 1694 Nashville - 2739 Lake Charles

CM

50 .

•40.0

30.

0

30.0

10 . 0

0.0 0.0

100 150 200 250 300

Cooling degree days x 10

-1

Figure 20. Cooling and heating energy consumption of case 11

(classrooms and offices) — base dual-duct

49

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

3.0

o0. e 2.5

2.0

I.!

0.0

CDD CITY

84 Santa Maria

129 Seattle

460 Madison

1415 Washington

1694 Nashville

2739 Lake Charle

S0.

0

CM

C

- - 40.0

30.

0

20.0

10 . 0

“I 1 1 1—*“l 1 1 1 1 1 1 T— 0.0

50 100 150 200 250

Cooling degree days x 10

300

60.0

50.0 f

40 . 0

30.0

20.0

10.0

0.0

Figure 21. Cooling and heating energy consumption of case 12

(classrooms and offices) — base dual-duct with enthalpy

economy cycle

50

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

CM

60.

0

50.0

•JO . 0

30.

0

20 . 0

10.0

0.0

Heating degree days x 10

Figure 22. Cooling and heating energy consumption of case 13

(classrooms and offices) -— base dual-duct with enthalpy

economy cycle and hot air temperature reset

51

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

Figure 23. Cooling and heating energy consumption of case 14

(classrooms and offices) — base dual-duct with hot and cold

air temperature reset

52

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

1C>

Btu

Yearly

cooling

energy,

10

Btu

3. U

CM CDD CITY

64 Santa Maria

129 Seattle

460 Madison

1415 Washington

1694 Nashville

2739 Lake Charle

DCAL DUCT

Case 11 —base DD Case 12 —enthalpy economy

Case 13—enthalpy economy

hot air reset Case 14—base DD + hot 4 cold

air reset

-- 60. 0

- - 50. a

-- 40.0

1.5

1.0

-- 30.

a

-- 20.0

-- io. a

o.o e.a

100 150 Cooling degree days x 10

300

Figure 24. Cooling and heating energy consumption of cases 11 through 14

(classrooms and offices) — all dual-duct cases

53

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10^

Btu

CM

60. 0

so.

•jo. o

30.0

20.0

10. 0

0.0

60.0

S0.0

JO. 0

30.0 u

m

20.0 <u j:

>> fH 10.0 £

0) «

0.0

Figure 25. Cooling and heating energy consumption of case 15

(classrooms and offices) — unit ventilator system

54

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

1(T

Btu

Yearly

cooling

energy,

10

Btu

a.e

CM CDD CITY

84 Santa Maria

129 Seattle

460 Madison

1415 Washington

1694 Nashville

2739 Lake Charle

Case 5—base RH + enthalpy economy +

zone reset Case 10—base VAV + enthalpy economy + zone reset Case 14 —base DD +hot & cold air reset Case 15—unit ventilator

be. a

se. a

•jo . o

3

i-i 03

occ

3c

4)noc

o0

u

I—

I

c

CO

01 >*

no

Ci

0)c

0)occ

•HO

Cfl 0) JZ

i-HCl

CO

0) >*

Figure 26. Cooling and heating energy consumption of cases 5, 10, 14,

and 15 (classrooms and offices)

55
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

5B.0-

40.0

30. 0

20 0

10 . 0

e.e

Figure 27. Cooling and heating energy consumption of case 16 (entire

school) — case 1 for classrooms and offices, base systems

f° r non-classroom/office areas, all systems on for

10 hours a day

56

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10 3

Btu/ft
Yearly

heating

energy,

10

Btu

YearLy

cooling

energy,

10

Btu

50.0 ^

40.0

30. 0

:u.u

10. 0

0.

0

Figure 28. Cooling and heating energy consumption of case 17 (entire

school) — case 1 for classrooms and offices, base svstems

for non-classroom/office areas, all systems on

according to occupancy schedules

57

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10 9

Btu

3.e se. e

2.5

2.0

t

T

1 .

0

CDD CITY .

84 Santa Marla • 129 Seattle . 460 Madison

1415 Washington

1694 Nashville -- 2739 Lake Charles

C. 0

r

-t- e

-- 10.0

0 . 0 300 Cooling degree days x 10

Heating degree days x 10

50.0

40.0

30 . 0

20.0

10 . 0

0.0

Figure 29. Cooling and heating energy consumption of case 18 (entire

school) — case 3 for classrooms and offices, enthalpy

economy cycle for non-classroom/office areas

58

Yearly

heating

energy,

10

Btu/il

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

3.0 5-e e

0.5 t

CDD CITY

84 Santa Karla

129 Seattle

460 Hadison

1415 Washington

1694 Nashville

2739 Lake Charle

>.5 -j0.0

100 150 000 050

Cooling degree days x 10

-1

--43.0

j1

A

so. e

:o. o

13 e

0.e

30c

: igure 30. Cooling and heating energy consumption of case 19 (entire

school) — case 5 for classrooms and offices, enthalpy

economy cvcle for non-classroom/of f ice areas

59

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
Yearly

heating

energy,

10

Bt,u

3.0 tee

CDD CITY

2 2.5- 84 Santa Maria

CQ 129 Seattle

O'o 460 Madison

_l 2.0 - h 1415 Washington

1694 Nashville

ocu 2739 Lake Charles

0 50 100 ISO 000 050 300 Cooling degree aays x 10

CN

40 0

30 0

20 0

10.0

0.0

Figure 31. Cooling and heating energy consumption of case 20 (entire

school) — case 6 for classrooms and offices, base systems

for non-classroom/office areas

60

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

1Q

J

Btu/ft
Yearly

heating

energy,

II) 9

Btu

Yearly

coolln

*

e

"

er

RX.

10»

tu

50.0 ^

42 e

30 . 0

tu.e

;a. a

e.e

50 2

40 a

30 a sc

20 a

10 0

a a

Figure 32. Cooling and heating energy consumption of case 21 (entire

school) — case 5 for classrooms and offices, enthalpy

economy cycle non- c 1 a s s r oom/ o f f ic e areas

61

Yearly

cooling

energy,

10

Htu/ft
Yearly

cooling

energy,

10

Btu

CN

3

d_i ec

u

u

01ca

occ

CM

>>

ac

a;

3/ac

>>b

u

>>

Figure 33. Cooling and heating energy consumption of case 22 (entire

school) — case 10 for classrooms and offices, enthalpy

economy cycle for non-classroom/off ice areas

62
Yearly

cooling

energy,

10

Btu

heating degree days x 10

sa. e

4Q. a

30. a

20. a

10. a

e.e

Figure 34. Cooling and heating energy consumption of case 23 (entire

school) — case 11 for classrooms and offices, base systems

for non-classroom/of f ice areas

63

Yearly

heating

energy,

IQ 3

Btu/ft

2

cooling

energy,

10

Btu/ft
Yearly

cooling

energy,

10

Btu

se.e

fN

40 a

ae. e

20.0

i0 e

e.a

Heating degree days x 10

Figure 35. Cooling and heating energy consumption of case 14 (entire

school) — case 13 for classrooms and offices, enthalpy

economy cycle for non-classroom/office areas

64

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10 3

Btu/ft
Yearly

heating

energy,

10

litu

Yearly

cooling

energy,

10^

Btu

3.0 se. a

2.5

2.0

1.5

CDD CITY

64 Santa Maria

129 Seattle —

460 Madison

1415 Washington

1694 Nashville

2739 Lake Charles i

-- 40 3

3

4J

cc rn

>>oC

1 .

0.0

— 20 3

Cooling degree days x 10

ccc

-r 10 3

0.3

Figure 36. Cooling and heating energy consumption of case 23 (entire

school) — case 14 for classrooms and offices, enthalpy

economy cvcle for non-classroom/office areas

65

Yearly

heating

energy,

10

Btu/ft
Yearly

heating

energy,

10

Btu

Yearly

coollng

energy,

10 9

Btu

“M

atu

0)c

0)

at

TO

01 s:

>su

TOU

>-

Figure 37. Cooling and heating energy consumption of case 25 (entire

school) — case 15 for classrooms and offices, enthalpy

economy cycle for n on - c 1 a s s r o om / o 1 f i c e areas

66
Yearly

heating

energy,

10

Btu

Yearly

cooling

energy,

10

Btu

3.0 st).

a

CNI

2.5 --

2.0 --

1.5

1.0

CDD CITY

84 Santa Maria " 129 Seattle

460 Madison

i 1415 Washington — 1694 Nashville

; 2739

o

Lake Charles

-- 40.

a

-- 30.8

20 . a

Case 16—systems on 10 hours a day Case 17 —systems on during occupied hours

10.0

0.0 1 1 1 1 1 1 > r- —i

1 1 r I 1 1 1 1 1 1 1 r- 0.0

50 100 150 200 250

Cooling degree days x 10

^

300

50 . 0

40.0

30 . 0

20.0

10 . 0

0.0

Figure 38. Cooling and heating energy consumption of cases 16 and 17

(entire school)

Yearly

heating

energy,

10

Btu/ft

Yearly

cooling

energy,

10

Btu/ft
NBS-114A (rev. 2 -ac) U.S. DEPT. OF COMM. 3. Publication Date

March 1984

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 84-2831

2. Performing Organ. Report No.

4.

TITLE AND SUBTITLE

Strategies for Energy Conservation for a School Building

5. AUTHOR(S)

James Y. Kao

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7. Contract/Grant No. national bureau of standards

DEPARTMENT OF COMMERCE I. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. Stote, 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

| | 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 education 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 an elementary school. The

HVAC systems simulated are constant volume reheat, variable air volume, dual-duct,

and unit ventilator systems. The control strategies tested are dry-bulb temperature

economy cycle, 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) school building control strategies; school building energy conservation; school

HVAC systems; school building thermal performance.

13.

AVAILABILITY 14. NO. OF

PRINTED PAGES

[X] Unlimited

| | For Official Distribution, Do Not Release to NTIS

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

77

15. Price

pTj Order From National Technical Information Service (NTIS), Springfield, VA. 22161 $11 .50

USCOMM-DC 6043-P80