NAT'L INST. OF STAND & TECH

AlllOb bTOESl

NBSIR 75-683

The Effect of Attic Ventilation on the

Energy Required to Air Condition a

One-Story Building

C. I. Siu, C. M. Hunt, and T. Kusuda

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

August 4, 1975

Final Report

Prepared for The Tri-Services

QC

100

.U56

75-683

1975
(
NBSIR 75-683

THE EFFECT OF ATTIC VENTILATION ON THE

ENERGY REQUIRED TO AIR CONDITION A

ONE-STORY BUILDING

C. I. Siu, C. M. Hunt, and T. Kusuda

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D. C. 20234

August 4, 1975

Final Report

Prepared for Hie Tri-Services

U.S. DEPARTMENT OF COMMERCE, Rogers C.B. Morton, Secretary

James A. Baker, III, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Qirector

The Effect of Attic Ventilation on the Energy

Required to Air Condition a One-Story Building

C. I. Siu, C. M. Hunt, and T. Kusuda

Thermal Engineering Section

Building Environment Division

Center for Building Technology

5 Institute for Applied Technology

ABSTRACT

Measurements were made on a masonry building at Fort Myer , Arlington,

Virginia to determine the effects of attic ventilation on energy require10 ments for air conditioning. Also, the National Bureau of Standards Load

Determination computer program, NBSLD, was used to calculate the hourly

room and attic air temperatures of this building for different values of

attic air changes and the results were compared with measured values.

Except for one day of testing, weather conditions during the testing

15 period were similar. Experimental results for test periods of similar

weather conditions indicated that the energy for air conditioning was

greater, by as much as 7 percent, with attic fan in operation than without. In addition, in one case the total energy consumption (air conditioner plus attic fan) with attic fan in operation was found to be great2 0 er by as much as 17.5 percent, than that in which the attic fan was inoperative.

i
The values of the hourly room air temperature calculated using NBSLD

were within 6 F (-14 °C) of the measured values. The calculated values

of the attic air temperatures for attic ventilation rates of 0.7 and 5

air changes per hour were within 10 F (-12 °C) and 5 F (-15 °C), respec5 tively, of the measured values.

\ Some general guidelines regarding the application of attic ventilation to other buildings are derived from this study.

Key Words: Attic air temperature; attic ventilation; energy

conservation

ii
TABLE OF CONTENTS

Page

1. Introduction 1

5 2. Building 219, Fort Myer 1

3. Instrumentation

.

3

4. Experimental Procedure 6

5. Results 7

5.1 Experimental Results 7

10 5.2 NBSLD Results 12

6. Discussion 13

7. Conclusions 16

8. Acknowledgments 17

9. References 17

15 10. SI Units 17

Figures 1 through 10 19

iii

1. Introduction

Air conditioning techniques which lead to a reduction of energy requirements in buildings without impairing the health or aggravating illnesses of the occupants or without causing too much discomfort to the

occupants are most desirable. It has often been speculated that attic

ventilation leads to a reduction in the energy requirements for air conditioning. Experimental data relating to this conjecture are lacking.

However, computer programs such as the National Bureau of Standards Load

Determination, NBSLD, exist which are able to determine the validity of

this conjecture.

The objectives of this work were to gather experimental data in order to determine the effect of attic ventilation on energy consumption

and to compare NBSLD temperature predictions with experimental data. For

this purpose, measurements were made on the Facilities Engineering Building (Building 219) at Fort Myer , Arlington, Virginia. Room temperature

as a function of attic ventilation was of particular interest.

2. Building 219, Fort Myer

The Facilities Engineering Building, Building 219 (Figure 1), at

Fort Myer, Arlington, Virginia was selected for this study. The building was built in 1895* to serve as a granary. After World War II, it

was remodeled into an office building-'. Presently, about two thirds of

Building 219 is used for offices; the remaining one third consists of a

plumbing shop (Figure 1).

Information furnished by the Office of Facilities Engineering.
Building 219 is made of red brick and has a gable roof. The gables

face the north-south direction. Building 219 (offices) used in this study

was 23 ft. (7 m) high. The basic construction data of Building 219 are

given in Table 1. Figure 2 is a schematic diagram of the floor plan of

5 that portion of Building 219 which was used in this study.

Table 1 Basic Construction of Building 219

Construction Material

10

roof green slate, 1/2 in. (1.3 cm)

wood sheathing, 7/8 in. (2.2 cm)

attic wall red brick, 13 in. (33.0 cm)

attic floor fibrous glass wool insulation, 6

in. (15.2 cm)

gypsum board, 1/4 in. (0.6 cm)

15

room wall red brick, 13 in. (33.0 cm)

air space, 3/4 in. (1.9 cm)

gypsum board, 3/8 in. (0.9 cm)

room floor asphalt tile, 1/8 in. (0.3 cm)

wood floor, 3/4 in. (1.9 cm)

wood subfloor, 2 in. (5.1 cm)

window single pane glass

Other information about Building 219 pertinent to this study is giv20

en in Table 2

.

2
Table 2 Additional Information About Building 219

10

Lighting

Occupancy

Central Air Conditioner

Total Floor Area

Window Area: east wall

south wall

west wall

Door Area: west wall

9,800 watts

2 0 persons

9

5 ton* (1.5 X 10 Joules)

3,255 sq. ft. (325 )

12 0 sq. ft. (11 m^)

4.5 sq. ft. (0.4 m2)

155 sq. ft. (14 in2)

50 sq. ft. (4.6 m^)

For purposes of NBSLD calculations, the sensible heat output

is assumed to be 45,000 Btu/hr (16 kw) based upon the sensible heat ratio of 0.75 and the total capacity of the air con- ditioner of 5 ton (1.5 X 10^ Joules).

15

3. Instrumentation

Figure 1 is a photograph of Building 219 prior to instrumentation.

The louver in the south gable was the only ventilation port in the building (see Figure 1). It was necessary to construct a ventilation port at

the north end of the attic. This was done by using a 12 in. (30 cm) flexible canvas duct. The duct was made to pass through the window and ceil2Q ing. The assembled duct is shown in Figures 3A and 3B. A 1/2 hp (373

watt) centrifugal fan was used to provide attic ventilation. A box-attachment assembly was built to permit attachment of the blower to cover

the existing ventilation louver. The attic louver was about 11 ft. (3.3

m) above ground so that it was necessary to use scaffolding to set the

2^ blower as close as possible to the louver, Figure 4.

3
Attic air change rates were determined by a tracer-gas technique

and by use of a calibrated hot wire anemometer. In the tracer method,

a small amount of sulfur hexafluoride gas, SF, , was introduced into the

D attic inlet port with the attic fan on. The concentration of SF, was

6

5 monitored at the attic outlet. When a concentration of the order of 12-

15 parts per billion was reached, and the rate of increase slowed, the

tracer was turned off. Monitoring of the gas at the attic exhaust was

continued. Ventilation rate was estimated from the rate of decay of

tracer concentration. The tracer gas was also used to measure the fan

10 exhaust rate by determining the degree of dilution when tracer was introduced into the fan at a known rate.

In the anemometer method measurements were made at the fan exhaust

by scanning at a total of twelve points, six in the vertical and six in

the horizontal positions with each point corresponding to an equivalent

15 concentric flow area. The fan exhaust rate obtained from these measurements and the volume of the attic were used to estimate the ventilation

rate. A similar estimate was made from tracer measurements.

Solar radiation was determined by use of a calibrated pyranometer

positioned at the south end of Building 219. The pyranometer was at the

20 same height as the top of the roof but placed at a distance 8 ft. (2.5

m) away from the gable at the south end of the building. A millivolt

recorder with digital printout was used to record the output from the

pyranometer

.

4
Four thermocouples were fixed to the outside surface of the roof using adhesive tape. Two of these thermocouples were located at the centers of two equal halves of the east facing roof surface. Likewise, two

thermocouples were located at similar positions on the west facing roof.

5 These thermocouples were used to determine the temperature of the surface

of the roof.

Four thermocouples were used to determine the attic air temperature.

These were located plumb with the thermocouples at the roof surface and

were placed at a distance mid-height between the roof and the attic floor.

I

j 10 Four thermocouples were used to determine the temperature of the attic

floor. These were located about an inch above the attic floor insulation

material and were plumb with the thermocouples used to determine the attic air temperature.

Room and ceiling temperatures were determined only for the large of15 fice located in the northwest corner of Building 219. The ceiling temperature was determined from a thermocouple attached to the ceiling using

adhesive tape. This thermocouple was located within a few feet of the

central air conditioner shown in Figure 2 . A thermocouple suspended below the ceiling thermocouple at mid-height distance was used to determine

2 0 the room temperature. A thermocouple was suspended under the eaves, located just outside of this room, to determine the outdoor air temperature.

This thermocouple was placed in the center of a 3 1/2 in. (25.4 cm) diameter aluminum foil cylinder to shield it from direct solar radiation.

A thermocouple was placed at the outlet of the central air condition25 er to determine the outlet air temperature. Indoor and outdoor wet-bulb

temperatures were determined using a sling psychrometer

5
Power to the central air conditioner and blower were monitored using

i watt-hour meters. The window air conditioner unit was not in operation

throughout the testing period.

The central air conditioner, shown as AC in Figure 2, was automati5 cally controlled by fixing the setting of the thermostat in the room at

76 F (24 °C).

4. Experimental Procedure

The energy consumption of the central air conditioner of Building

10 219 was monitored when the attic fan was turned off and when the attic

was subjected to various modes of ventilation. The experimental attic

intake duct was left open throughout the testing period. Ventilation

was accomplished by turning the blower on. Three separate modes of ventilation were used: continuous, cyclic and selective. In the continu15 ous mode, the blower was allowed to operate continuously for a period of

48 hours. In the cyclic mode, the blower was left on for a period of 4

hours and turned off for a duration of 4 hours. This cycle was followed

for a complete day. Two selective modes were followed. The blower was

left on during the night and cut off during the day. In the other selec2 0 tive mode, the blower was turned on whenever the attic air temperature

was 14 deg F (8 deg C) above the outdoor ambient air temperature.

All data, temperatures, solar radiation, watt-hour meter readings,

etc., were recorded at the beginning of each hour for a period of one

week (August 27 - September 3, 1973). Results of NBSLD calculations were

2 5 compared with measured values.

6
5. Results

5.1 Experimental Results

Values of hourly records are given in Figures 5, 6, and 7. Actual

2

solar radiation intensities are obtained by subtracting 11 Btu/ft -hr

5 2

(1.25 X 10 Joules/m hr), the background noise level of the pyranometer,

from values shown in Figure 5. Figures 6 and 7 also include the operation modes of the blower (which shall be referred to as an attic fan for

purposes of discussion). The measured values of attic air change rates

when the attic fan was OFF and ON are given in Table 3. It can be seen

that an attic air change of 0.7 air changes per hour occurred when the

attic fan measurement of fan delivery rate was not in operation.

Table 3 Attic Ventilation Rates in Building 219

Measurement Method

Air Changes

Per Hour

ATTIC FAN OFF

ATTIC FAN ON

Hot wire anemometer scan of fan

exhaust

Hot wire anemometer scan of fan

exhaust

Measurement of the fan exhaust

rate by measuring dilution of

tracer

Measurement of decay rate of

tracer concentration at attic

exhaust

0.7

4.8

5.1

4.8

Maximum values of solar radiation were recorded at about noon of

each day (Figure 5). Wet -bulb temperatures were maximum and minimum at

about the 16th and 5th hour of each day, respectively (Figure 5).
The outdoor air temperature was at a maximum value at about the 16th

hour of each day (Figures 6 and 7). This also corresponded to the time

at which the temperature of the surface of the west-facing roof was at

its maximum value. The maximum temperature of the surface of the east5 facing roof occurred about four hours earlier (Figure 6). The temperatures of the room air, ceiling, attic floor and attic air closely followed that of the outdoor air temperature (Figures 6 and 7). Temperature

ranges are summarized in Table 4. Weather conditions and the various

modes of attic fan operation are also included in this table.

10 Solar radiation (Figure 5 and Table 4), outdoor air temperature

(Figures 6 and 7 and Table 4) and weather conditions (Table 4) were similar from one test day to the next day during August 27, 1973 to September 3, 1973. Rain occurred at about the 16th hour of September 2, 1973

and lasted for three hours. Thus, except for the last day of testing,

15 any significant changes should not be attributed to variations in daily

weather.

The energy consumption of the central air conditioner and attic fan

for the various modes of attic fan operation are given in Table 5.

Average values of outdoor, room, ceiling and attic floor tempera20 tures for various modes of fan operations are presented in Table 6.

Figure 8 gives differences between attic air and outdoor air temperatures, T^, for the various modes of attic fan operation. In general, T^ begins to decrease at about the 2 0th hour to a minimum value at

about the same time at which the outdoor temperature reaches it maximum.

25 Shortly after sunrise, T^ attains a local minimum, then it advances to

its maximum value somewhere between the 19th and 20th hour.
9
Table 5 Energy Consumption of the Central Air Conditioner and

Attic Fan in Building 219 for Various Modes of Attic

Fan Operation+

Attic Fan Mode

Daily Energy Consumption (kw-hour)

Air Con- Attic

ditioner Fan

Difference**

Total (%)

0. Cyclic: 4-hour ON/OFF cycle

ON at 0800

139.3 8.44 147.74 4.2

10

1.

2.

3.

OFF: 0800-0800^

ON: whenever T > T + 14* aa o OFF: otherwise

OFF: 0800-2 000

ON: 2 000-0800

14 1 . 7 0 14 1 . 7

146.3 3.66 150.0

151.4 8.54 159.94 12.8

4. ON: 0800-0800^ 150.4 16.71 166.57 17.5

+

15

Attic fan capacity: 5 air changes per hour.

Continuously for 48 hours.

T and T denote attic and outdoor air temperatures, respectively.

**

^ _ (Total consumption: fan mode) ~ (Total consumption; mode 1) ^ ^^qq (Total consumption: mode 1)

20 1 kilowatt-hour = 3.4130 x 10 Btu.

10
Table 6 Average Temperatures (F)** for Various Modes of Fan Operation

^ Office Attic +

Mode Outdoor Room OR Ceiling Floor CA

0 81.6 76.2 5.4 77.1 89.2 12.1

1 85.8 76.7 9.1 77.3 94.8 17.5

2 86.8 78.1 8.7 79.6 95.7 16.1

3 87.8 79.4 8.4 80.8 95.6 14.8

4 87.5 78.6 8.9 79.5 94.5 15.0

T denotes the difference between outdoor and room temperatures. OR

t„^ = 5 (tp - 32)/9.

^ T . denotes the difference between attic floor and office ceiling

temperatures.

11
The difference between attic and outdoor air temperatures, for all

modes of attic ventilation, was greater than 14 deg F (7.8 deg C) for a

duration of about 7 hours, from the 14- 15th hour to the 21-22nd hour.

During this period, the largest difference between attic and outdoor air

5 temperature was obtained when the attic fan was ON during the night and

early morning and OFF during the day. The smallest difference between

attic and outdoor air temperature was obtained in the mode where the attic and outdoor air temperature was obtained in the mode where the attic

fan was turned on only when this difference exceeded 14 deg F (7.8 deg

10 C).

Figure 9 gives measured values of temperatures, AT, between the attic floor, T . ^1 , and the office ceiling, T , for Modes 2, attic floor ^ ceiling

4 and 5 relative to Mode 1 (fan completely off). Figure 9 indicates that

operation of the attic fan led in general to a smaller value of AT.

15

5.2 NBSLD Results

Calculations using NBSLD give 1.07 x 10 Btu (313 kw-h) as the total daily cooling load of Building 219.

NBSLD computed and measured hourly values of room and attic air tem2 0 peratures are shown in Figure 10, comparing continuous operation and fanoff conditions. The computer analysis correctly predicted the times of

maximum and minimum attic temperatures, but predicted a greater temperature change due to increased ventilation than was observed. The agreement between the observed and calculated temperatures was much closer

25 when averaged over a 24-hour period than it was at the maximum or minimum. In the fan-off condition a 24-hour average temperature of 98 F

12
(37 °C) was observed, while the computed value was the same. In the fanon condition 96 F (35 °C) was observed and 92 F (33 °C) computed.

In the office space, comparison between computed and observed values was available only for the fan-off condition. However the computed

5 curves for 0.7 and 5 air changes per hour did vary significantly. A maximum divergence of 4 deg F (2 deg C) was obtained. However at 0.7 air

changes per hour the measured temperature averaged about 2 1/2 deg F

(1.4 deg C) higher with the fan on than with the fan off.

6. Discussion

10

Figure 9 and Table 6 indicate that, on the average, the temperature

difference between the attic floor and the ceiling below decreases when

an attic fan was in operation. Thus, the usefulness of attic ventilation

is suggested. However, it cannot be concluded from this alone that the

15 energy consumption of the air conditioner will also be reduced. Other

factors such as infiltration, building construction, weather conditions,

and outdoor air temperature must also be considered.

Applying the expression Q = UaT, where U is the coefficient of transmission to the ceiling construction of Building 219 and using the mea3 20 sured mean value of AT across this element, one arrives at Q = 2.5 x 10

Btu/hr (0.73 kw) when the attic fan was not in operation (Mode 1). The

3

average downward flow of heat through the attic floor, 2.5 x 10 Btu/hr

(0.73 kw), represents about 5.6 percent of the total heat load of 4.5 x

4

10 Btu/hr (13.2 kw) as computed using NBSLD. With the attic fan oper3

2 5 ating continuously (Mode 4), Q correspondingly .becomes 2.1 x 10 Btu/hr

3

(0.61 kw). A reduction of 0.4 x 10 Btu/hr (0.12 kw), i.e., 16 percent,

13
of the downward heat load through the attic floor is obtained. This reduction corresponds to less than one percent of the total cooling load

as calculated by NBSLD. It is seen from Table 5 that energy consumption

3

of the air conditioner was increased by 1.0 x 10 Btu/hr (0.36 kw). This

3

^ value exceeds the beneficial decrease in cooling load of 0.4 x 10 Btu/hr

(0.12 kw). Adding the energy required to operate the fan decreases further the beneficial effects derived from the operation of the attic fan.

This conclusion is applicable to the other modes of fan operation; however, in the case of Mode 0 differences in weather conditions must be

taken into account.

The above result is compatible with the conclusion drawn by Nelson

et . al. [1], who made simulation calculations on a 900-square foot (274

2

m ) 2 -bedroom house having a maximum of 4 inches (10 cm) of fibrous glass

insulation in the attic floor and concluded that it was not economically

feasible to ventilate the attic using a fan.

Now if air leakage through the attic floor were of such a magnitude

that the sensible heat associated with such infiltration exceeded the reduction in cooling load which arises from the decrease in temperature

gradients across. the attic floor and exterior walls, then, as generally

20 shown in Table 5, the demand for the cooling would increase with increased

usage of the attic fan. Increasing the air change rate in the office

space of Building 219 by 0.5 air change per hour, for example, would lead

to an 8 percent increase in the cooling load. This amount of air change

is realized if ten percent of the air removed by the attic fan originated

25 from the office spaces below.

14
In siimmary, using an attic fan to draw outdoor air through the

space between ceiling and roof can affect the air conditioning load of

the rooms below in the following two ways:

1. It can reduce the downward heat flow through the ceiling,

5 if the attic temperature is lowered appreciably.

2. It can increase infiltration of outdoor air into the airconditioned rooms if there are air passages through the

ceiling construction, such as loose-fitting trap doors,

pipe chases, leaks around ducts that penetrate the ceil10 ing, etc.

These two processes would typically have opposite effects on the

air conditioning load and would tend to cancel each other.

The beneficial effect from reduction of attic temperature by attic

ventilation will be small in buildings such as Building 219 at Fort Myer

15 having the following characteristics:

a. high thermal resistance in the ceiling

b. low thermal resistance in the roof

c. low thermal resistance in the walls of the air-conditioned

spaces

2 0 The operation of a fan for attic ventilation will typically increase

the infiltration in the spaces below the ceiling. To minimize this adverse effect, all cracks and openings between the attic and air-conditioned spaces should be sealed. These include loose-fitting trap doors,

poor-fitting ducts that penetrate the ceiling, pipe chases through the

25 ceiling, air leaks through studs spaces into the attic, and poor-fitting

penetrations of the ceiling by light fixtures.
Thus, both the workmanship in the ceiling-wall construction and the

thermal resistance of the ceiling in relation to roof and walls need to

be considered in any proposed addition of an attic fan to an existing

building.

5

7. Conclusions

Measurements of energy used to air condition Building 219 at Fort

Myer indicated that operating an attic fan to reduce the attic temperature resulted in a small increase in the energy used by the air condi10 tioner over a 24-hour period, whether the fan was operated intermittently or continuously. The increase amounted to about 7 percent when the

fan was on from 2 000 to 0800 and off from 0800 to 2 000 and approximately

3 percent when the fan was operated only when the attic temperature exceeded the outside temperature by more than 14 deg F (7.8 deg C). The

15 increase amounted to about 6 percent with the fan operated continuously.

These estimates do not include the energy used to operate the fan.

Total cooling load of the building calculated by NBSLD was 1.07 x

6 9

10 Btu (1.13 X 10 Joules) over a 24-hour period. Calculations of heat

transfer through the ceiling based on measured attic and room air tem20 peratures indicated that tjhe maximum reduction in total cooling load to

be expected with the fan operating would be less than 1 percent.

The reason for the increase in energy used by the air conditioner

has not been established experimentally, but a small increase in the ventilation rate of the occupied space with the fan operating could account

2 5 for increases in cooling requirement comparable with those observed.

16
8.^ Acknowledgments

The authors wish to thank two members of the Military Construction

Directorate, Mr. W. I. Jacob, Facilities Engineering Division, and Mr.

) W. Y. Sato, Engineering Division, for their kind assistance in making

5

Building 219 available for this study. The authors also wish to thank

Lt . Col. J. A. Sulik, Post Engineer, Fort Myer , and his staff for the

efficient manner in which all of our requests were fulfilled and for

their kind hospitality. The authors wish to thank Mr. P. R. Achenbach

of the Center for Building Technology, NBS , for his critical review of

10

the manuscript. The help provided by Messrs J. W. Bean, W. M. Ellis

and D. R. Showalter of the NBS staff is acknowledged.

9. References

1. L. Nelson et . al., Honeywell Interoffice Correspondence, "Attic

15

Ventilation - Effect on Air Conditioning Requirements", April 10,

. 1973.

10. SI Units

Familiar English units have been used in this report. To convert

20

to SI units the following conversions are given.

(tp - 32) 5/9 = t„^

inches x 0.0254 = meters

feet X 0.3048 = meters

25 sq. feet x 0 . 092 9 0 = sq . meters

cubic feet x 0.02 832 = cubic meters

17
Tons of refrigeration x 3.039 x 10 = Joules

Horsepower (electric) x 746.0 = watts

British Thermal Units (mean) x 1055.9 = Joules

2 2

Btu/hr ft x 3.1543 = watts/m

USCOMM-NBS-DC

18
19
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20



(dH-gid/nia) Noiiviavy yvios

a:

d '3ynivy3di/\i3i

24
Figure 6 Outdoor Air, Roof Surface, Attic Air, and Room Temperature.

(See Section 10 for Conversion to SI Units.)

25
Figure 7 Attic Air, Attic Floor, Room, and Ceiling Temperatures.

(See Section 10 for Conversion to SI Units.)

26
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27
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I6|—

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2 -

0800

AF= ATTIC FLOOR

C = CEILING

ATTIC FAN • OFF= 0800-0800

O 0N= 0800-0800

V OFF= 0800-2000

0N= 2000-0800

T 0N= 1430-1900

OFF: OTHERWISE

1200 1600 2000

TIME OF DAY (HOUR)

2400 0400 0800

Figure 9 Difference Between Attic Floor and Office Ceiling Temperature

for Several Modes of Attic Fan Operation. (See Section 10 for

Conversion to SI Units.)

28
TIME OF DAY (HOUR)

Figure 10 Comparison Between NBSLD and Measured Values for the Attic

Air Temperature for Different Attic Air Changes Per Hour

(Air Changes Per Hour Indicated in Parentheses). (See Section 10 for Conversion to SI Units.)

29
HBS-114A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLIC ATION OR REPORT NO.

NBSIR 75-683

2. Gov't Accession

No.

3. Recipient's Acces.sion No.

4. TITLE AND SUBTITLE

The Effect of Attic Ventilation on the Energy Required to Air

Condition a One-Story Building

5. Publication Date August 1975

6. Performing Organization Code

7. AUTHOR(S)

C. I. Siu, C. M. Hunt, and T. Kusuda

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 4624410

11. Contract/Grant No.

1 2* Spon sor ing Org anization Name and Complete Address (S treet, Ci ty , Stste , ZIP)

The Tri-Services

13. Type of Report & Period

Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

/

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

bibliography or literature survey, mention it here.)

Measurements were made on a masonry building at Fort Myer, Arlington, Virginia to

determine the effects of attic ventilation on energy requirements for air conditioning.

Also, the National Bureau of Standards Load Determination computer program, NBSLD, was

used to calculate the hourly room and attic air temperatures of this building for different values of attic air changes and the results were compared with measured values.

Except for one day of testing, weather conditions during the testing period were

similar. Experimental results for test periods of similar weather conditions indicated

that the energy for air conditioning was greater, by as much as 7 percent, with attic

fan in operation than without. In addition, in one case the total energy consumption

(air conditioner plus attic fan) with attic fan in operation was found to be greater,

by as much as 17.5 percent, than that in which the attic fan was inoperative.

The values of the hourly room air temperature calculated using NBSLD were within

6 F (-14 °C) of the measured values. The calculated values of the attic air temperatures for attic ventilation rates of 0.7 and 5 air changes per hour were within 10 F

(-12 °C) and 5 F (-15 °C), respectively, of the measured values.

Some general guidelines regarding the application of attic ventilation to other

buildings are derived from this study.

17. KEY WORDS (six to twelve entries; alphabetical order;' capitalize only the first letter of the first key word unless a proper name; separated by semicolons

)

Attic air temperature; attic ventilation; energy conservation

18. AVAILABILITY Unlimited

For Official Distribution. Do Not Release to NTIS

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' Order From Sup. of Doc, U.S. Government Printing Office Washington. D.C. 20402. SD Cat. No. C13

1 1 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

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21. NO. OF PAGES

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USCOMM-DC 29042-P74