A111D2 b23T51

NATL INST OF STANDARDS & JECH R.I.C.

A1 11 02623951

Kusuda. Tamaml/Savlngs In electric coo^l QC100 !U5753 NO. 1138 1981 V19 C.1 NBS-P Z%

V) J

NBS TECHNICAL NOTE 1138

NBS

PUBLICATIONS

U.S. DEPARTMENT OF COMMERCE/National Bureau of Standards

Savings in Electric Cooling Energy

By the Use of a Whole-House Fan
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress on March 3, 1901

The Bureau's overall goal is to strengthen and advance the Nation's science and technology

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the Institute for Computer Sciences and Technology.

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2 Some divisions within the center are located at Boulder, CO 80303.
Savings in Electric Cooling Energy

By the Use of a Whole-House Fan

T. Kusuda

J. W. Bean

Center for Building Technology

National Engineering Laboratory

National Bureau of Standards

Washington, D C 20234

This report was prepared under NBS STRS project 7421216 and NBS/CBT DACTAP project 7421219

^T °F oQt

%e*u of *

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

NATIONALBUREAUOF STANDARDS, ErnestAmbler, Director

Issued May 1981
National Bureau of Standards Technical Note 1138

Nat. Bur. Stand. (U.S.), Tech. Note 1 1 38, 39 pages (May 198 1) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1981

For sale by the c jperintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

Price $2.75

(Add 25 percent for other than U.S. mailing)
Savings in Electric Cooling Energy by

the Use of a Whole-House Fan

T. Kusuda and J. W. Bean

ABSTRACT

Hour-by-hour cooling performances of a typical ranch house, with and without

the use of a whole-house fan, were compared for the climate conditions

throughout the contiguous United States. The comparative analyses were

made by the use of NBSWHF, a modified version of NBSLD, to simulate the

complex thermal coupling of whole-house-fan ventilated attic space. The

calculations were performed for two operational modes: a cyclic fan mode

and a stepwise continuous mode. The calculation predicted a large cooling

energy savings as compared to the house without the use of the whole-house

fan, without significant deterioration of indoor thermal comfort.

Key Words: building thermal performance; energy calculation; energy

conservation; thermal comfort; whole-house ventilation.

111
ACKNOWLEDGMENT

The work reported in this Technical Note was sponsored by the National

Bureau of Standards. Part of the motivation for this analytical study

was the extremely beneficial results revealed in a limited field study

of the whole-house-fan approach to cooling. That field study was a minor

part of a DOE/NBS project sponsored by the U.S. Department of Energy.

The authors gratefully acknowledge DOE ' s interest and support of that

project, entitled Attic Ventilation Criteria, which was conducted in

Houston, Texas in 1977-78.

IV
CONTENTS

Page

ABSTRACT iii

ACKNOWLEDGMENT iv

1. INTRODUCTION 1

2. COMPUTER SIMULATION 2

3. TEST HOUSES 2

4. CALCULATED COOLING ENERGY CONSUMPTION 3

5. CONCLUSIONS 7

6. REFERENCES 7

1. INTRODUCTION

During the summer of 1977, NBS engineers conducted extensive tests on attic

ventilation in three unoccupied test houses in Houston, Texas . Although

this NBS test concluded that the attic fan was ineffective for savings in

cooling energy consumption, a limited study conducted on the attic wholehouse fan proved to be extremely beneficial.

While an attic fan is usually installed at the gable and draws the outdoor

air through gable and soffit ventilation openings, the attic whole-house fan

is mounted at the ceiling, and draws outside air through windows and exhausts

it through the attic space. The fan would be turned on whenever the outdoor

temperature is low enough to provide natural cooling. Since an average

whole-house fan would require 400 to 500 watts of electrical energy as contrasted to the 2500 to 3000 required for central air conditioning, it is

easy to see that significant electrical energy savings are possible by

substituting the use of a whole-house fan for a central air conditioner.

Most of the whole-house fans are designed to ventilate a house at 1/2 to 1 air change per minute. If the house temperature is to be maintained at a reasonably comfortable condition, the use of a whole-house fan could be

substituted for that of an air conditioner whenever the outdoor temperature

is less than about 82 °F.

Table 1 shows the number of hours during the year when the outdoor temperature is less than 82° but higher than 65° for ten different cities in the

United States. The lower limit of 65° was chosen because it would be

unlikely that either natural or whole-house ventilation would be used when

the outdoor temperature was that low. Natural ventilation simply by

opening windows (but without the fan running) may be sufficient below 72 °F.

The number of hours shown in Table 1 that occur when the outdoor temperature

falls within the 72-82° temperature bin, therefore, represents a potential

number of hours when the whole-house fan can be utilized.

The actual number of hours when the whole-house fan is used, however, depends

strongly upon the interaction between the building heat transfer and storage

characteristics with respect to the cooling potential of the outdoor air.

The actual electrical energy savings obtained by the use of the whole-house

fan is also dependent upon the manner in which it is operated. The purpose

of this study is to evaluate the effectiveness of whole-house ventilation by

simulating the detailed building heat transfer process with respect to the

mode of operation of a whole-house fan.

The whole-house fan may be activated as soon as the outdoor temperature falls

below a set point, and left running continuously not only to maintain the

comfort condition but also even to undercool the house. The undercooling is

done intentionally to store the coolness to counter the hot daytime condition

that follows. Unless carefully monitored, however, this mode of operation

may end up wasting a large amount of fan energy.
The wasting of the fan energy may be reduced by reducing the fan speed in

accordance with a predetermined control strategy. The fan also may be cycled

by an indoor thermostat. This paper addresses several selected modes of

whole-house-fan operation. Additional work is needed to identify the energy

savings potential of other possible modes of operation.

2. COMPUTER SIMULATION

The National Bureau of Standards Heating and Cooling Load Determination

Program, NBSLD, is a comprehensive hourly simulation computer program based on detailed radiant exchange heat balance among the interior surfaces of

the building, as well as the transient heat conduction through the various

components of the building envelope. Details of this program are given in

reference 2. NBSLD was first modified to simulate the detailed heat transfer

and thermal storage process of whole-house-fan operation. The modified

NBSLD, called NBSWHF, was then validated by comparing its results with the

measured results of the Houston test house. The modification is in the

attic temperature and heat transfer algorithm to account for precise radiant

heat exchange between the underside roof and attic floor surfaces. Also

included in NBSWHF are the capabilities to determine Fanger's Predicted Mean

Vote (PMV), which is a well-recognized comfort indicator. Figure 1 shows

the calculated and measured indoor temperature and cooling load of the Houston

test house for the whole-house-fan operating period covering September 2 7 through October 1 of 197 7. Except for the last day, the measured and NBSWHF

calculated cooling loads are in good agreement.

3. TEST HOUSES

Using this validated NBSWHF computer program, the simulation studies were

conducted for the Hastings Ranch House (a three-bedroom house with 1,176 ft^

floor area), which embodies current energy conservation designs and is more energy efficient than conventional houses. ' The computer model of the

house was, however, modified in accordance with the prevailing local building

practices and moved around to the ten cities listed in Table 1. The essential

features of the house are:

Floor:

Roof:

4-inch concrete slab-on-grade over 1

" rigid foam insulation for

California, Arizona, and Texas houses.

Wooden floor with R-7 insulation over crawl space for the Atlanta

and Portland houses.

Basement floor for the Washington, Minneapolis, and Chicago houses

22.6° pitched roof with 1-1/2 ft overhang over the walls.

R-19 attic floor insulation, except for the Minneapolis house,

which had R-22 attic floor insulation.
Walls :

° R-ll insulation with aluminum siding, except for the house in

California, which had stucco walls.

Windows ;

Double-glazed windows for Minneapolis, Chicago, Portland, and Washington.

Other data used such as window characteristics, air leakage datay and internal

heat source data were made consistent with those used in the DoE's Building

Energy Performance Standards (BEPS). Details for the BEPS residential building

data are given in reference 4. The building had 15% of floor area as the

glazing area, which was evenly distributed among all four walls. This assumption was intended to model current practice, in which windows are not preferentially oriented. An internal load of 15.5 kWh/day was distributed in accordance with a typical household lighting, cooking, appliance-use schedule, as well as the occupancy pattern. As to the air leakage data, it was assumed that

the infiltration under standard design condition is 0.6 air change per hour.

The hourly air change values, however, were adjusted with respect to actual

wind speed and indoor/outdoor temperature difference using the Achenbach and

Coblentz relationship. '

4. CALCULATED COOLING ENERGY CONSUMPTION

Tables 2 and 3 show the results of the NBSWHF calculations in terms of annual

cooling load comparison between the houses with and without the whole-house

fan, determined for the ten cities using ASHRAE TRY weather data tapes. '

The ASHRAE TRY weather data tapes contain hourly coincident values of outdoor

temperature, humidity, wind speed, wind direction, and cloud cover. In

NBSWHF the cloud cover data were converted into hourly solar radiation data

by the Kimura/Stephenson method. '

The whole-house fan may be operated in many different ways with regard to

starting/stopping, setting of the fan speed, and continuous vs cycling, etc.

In this study, the operation of the whole-house fan was simulated in two

different modes. In mode #1, the hourly total volume of the outside air

introduced into the house was precisely regulated to satisfy the net sensible

cooling requirements of the house for a 78 °F room temperature set point.

This was done in the following sequences:

(1) The hourly sensible cooling requirement without whole-house fan for

a given thermostat setting was first determined by a rigorous building

heat transfer calculation on an hourly basis.

(2) If the coincident outdoor temperature DB was below the indoor

thermostat setting 78° and yet higher than 70 °F, the necessary volume

of outdoor air to satisfy that cooling requirement was then calculated

by the following relation:

c f m = Sensible Cooling Requirement . 1.08 (78 - DB)
(3) The calculation for that hour was then repeated to determine the room and attic temperature under the condition when the air conditioner

was off and the whole-house fan would introduce the volume of air determined in step 2 on the basis that the room air was exhausted through the

attic space. In order for a given whole-house fan to deliver exactly

the right volume of air as determined by the equation in step 2, however,

it is intrinsically assumed that the fan is cycled. In other words, the

total running time of the fan was assumed proportional to the required

cfm as specified in step (2) divided by the full-load capacity of the fan

(to deliver an equivalent of 1 air change per minute of the house air.).

The second, iterative calculation showed that the whole-house fan was indeed able to maintain the room temperature at the set value within 1 °F

.

(4) The energy consumption of the fan was determined by multiplying the

standard power rating (in this example 450 watts) by the fan running

time. If the calculated air delivery rate exceeded the rated air delivery

rate of the fan, the rated fan air delivery rate was used.

Table 2 also lists the total number of hours of the whole-house fan operation,

estimated fan energy consumption, and estimated electrical energy savings on air conditioning (based upon the seasonal COP of 2.5) as a result of the

whole-house-fan use, as well as the net seasonal electrical energy savings

obtainable by the use of the whole-house fan.

In typical applications, however, the whole-house fan is not cycled by the room thermostat as simulated in the mode #1 calculation. It is operated

continuously with full capacity of one air change per minute as long as the

outdoor temperature is above 78°F but below 82 °F , with the room air conditioner

turned off. This mode of operation, designated as mode 2, was simulated

using NBSWHF. The whole-house fan in the mode #2 analysis is also assumed

to operate at half capacity (i.e., 0.5 air change per minute) when the outdoor

temperature is below 78 °F but above 7 2°F. When the outdoor temperature was below 72 °F it was also assumed that the fan was stopped and the house was cooled with natural ventilation of 6 air changes per hour, or one-tenth of

the standard whole-house-fan rate. The indoor temperature will be very close

to the outdoor temperature when the whole-house fan is introducing the outdoor

air with a rate of one air change per minute, which would create a breeze of

100 200 ft per minute. The breeze makes the occupant comfortable under higher

temperatures than 80°F, as shown in Figure 2, which depicts the Fanger comfort

index. The PMV stands for the "Predicted Mean Vote" and represents the

average thermal sensation of people representing many social strata and age

groups on the combined effect of temperature, humidity, mean radiant temperature, and air speed across the body. The scale for the PMV is as follows:
3 hot

2 warm

1 slightly warm

neutral

-1 slightly cool

-2 cool

-3 cold.

The physiological fundamentals of PMV with respect to thermal environment,

effect of sex, race, age, food and other factors are given in reference 3.

Figure 2 shows also that the full-capacity whole-house-fan breeze (100~200 fpm)

would make the occupant feel too cool if the room temperature were below

80°F. This is the reason that the fan capacity was assumed to be cut down

to a half of full capacity. Furthermore, it was assumed that the natural

ventilation without fan could provide approximately 6 air changes per hour of

outdoor air circulation and is good enough to provide a comfortable condition

when the outdoor temperature is below 72°F but above 65°F.

Table 3 shows the result of the mode #2 calculations for the same houses used

in the mode #1 simulation. A marked increase in the electric energy savings

is mostly due to the fact that the number of hours when the fan is on (WHF

hours) to replace the air conditioner is larger than in the mode #1 operation.

The increase of the cooling kWh savings was, however, somewhat offset by the

increased fan energy consumption. The fan power in this case was estimated by

examining typical commercial whole-house fan ratings and was assumed to be 450

watts at full capacity and 130 watts at half capacity. It appears that the

electrical power consumption varies with 1.7 power of air delivery rate while

the theoretical fan brake horse power should vary with the cubic power of the

air delivery rate, in accordance with the fan law. The deviation from the

fan law is due to the reduction in the electrical motor efficiency as its rpm

is reduced.

Figures 3 through 12 show the daily cooling kWh plotted versus daily average

outdoor temperature for the ten cities used in the analysis. For this

analysis, the whole-house-fan was operated in mode #2. Most of the figures

show the marked decrease of the daily cooling kWh when the whole-house-fan

was utilized, except for Phoenix and Fresno, where the cooling kWh savings

are somewhat smaller than in the other cities. This is because the percentage

of possible whole-house fan hours during the summer in these two cities is

considerably smaller than in the other cities, as shown in Table 1 and Figure

24. The two straight lines shown in these figures are least-squares-fit

representations of the calculated daily total cooling kWh points.

Figures 13 through 22 show the hourly frequency of calculated PMV's for the

houses with and without the use of whole-house ventilation. These hourly frequency profiles under shaded histogram represent the house without whole-house

fan, while the unshaded histograms represent the house with whole-house fan.

The house with a whole-house fan operated under mode 2 tends to show many hours

with higher PMVs. The PMVs in these calculations, however, were calculated on the basis of a predetermined set of occupancy responses to the hot environments

as follows:
1) The occupant wears typical business suit (clo = 1.0). The room air

motion is zero.

2) When the occupant feels warm as the indoor temperature increases

(PMV = 2.0), he starts shedding his clothes until the clo value

becomes 0.5 or the equivalent of light summer clothing.

3) If the PMV value is still higher than 2 . at clo = 0.5, the PMV is

recalculated with increased air speeds at steps of 0.1 m/s until

0.5 m/s is reached.

In figures 13 through 22, the PMV values in the abscissa are shown to represent

these three conditions. Although these figures clearly indicate that the use of

whole-house fans would shift the comfort profile toward "warm," a majority of

occupants would be comfortable even during the hottest period of the season by

wearing light clothes and staying in the breezy areas in the house. The same figures also indicate that the whole-house fan would make the occupant feel cool

in many hours during the year unless he wears heavy clothes and stays in nonbreezy areas.

The higher PMV values shown in Figures 13 through 22, especially for the

whole-house fan calculation, could therefore be reduced by as much as 1.0, if

they were evaluated at 0.5 clo and at 0.5 m/s (or approximately 100 fpm)

instead of zero. In other words, a thermal comfort level of about 1.0

(slightly warm condition) could be maintained throughout the summer for all

of the whole-house-fan houses in the United States.

In order to compare the cooling kWh effectiveness of the whole-house fan at

indoor thermostat settings other than 78°F, figure 23 is prepared for the

Washington, D.C. ranch house. This figure was obtained for the mode #1

condition so that the effectiveness of the whole-house fan could be compared

at identical indoor conditions. It is shown also that the relative amount of

cooling kWh saving becomes greater as the indoor cooling thermostat is set at

a higher temperature. The implication of this particular figure is that an equal or greater amount of cooling kWh savings can be obtained simply by

increasing the cooling thermostat setting without even using a whole-house

fan. For example, the annual cooling kWh reduction by whole-house fan at

78°F for the Washington D.C. ranch house is from 2500 kWh to 1900 kWh, or 600 kWh. Figure 23 shows that the same kWh savings can be obtained by simply

turning the thermostat from 78° to 82°F. The comfort aspect at 82°F can be

made similar to that of 78°F by using ceiling fan or similar room circulating

fan as long as the room humidity level is not excessive.

This point merits attention for economic considerations, since the cost of

purchasing and installing a whole-house fan is not trivial.
5. CONCLUSIONS

A large amount of net cooling energy savings — as much as 56 percent — is

possible by replacing the air conditioner with a whole-house fan, without

causing undue thermal discomfort.

Cooling energy savings by the use of a whole-house fan appear to be less

effective in desert climates such as Phoenix and Fresno, than in other

cities. It is generally true that the cooling kWh savings become greater as the number of potential hours for whole-house ventilation increases, as shown in Figure 23.

More studies are needed to develop the sensitivities of major parameters and

the effectiveness of whole-house cooling — such as house thermal mass,

indoor thermostat setting, and size of the whole-house fan. Also to be

included in the future studies are economic analyses as well as the indoor

relative humidity problems (when the outdoor air humidity level is high).

6 . REFERENCES

1. D.M. Burch and S.J. Treado, "Ventilating Residences and Their Attics for

Energy Conservation, " Summer Attic and Whole-House Ventilation, NBS

Special Publication 548, pp. 73-104, June 1979.

2. T. Kusuda, "NBSLD, the Computer Program for Heating and Cooling Loads

in Buildings," NBS Building Science Series 69, July 1976.

3. P.O. Fanger, "Thermal Comfort — Analysis and Applications in Environmental

Engineering." McGraw-Hill Book Co., 1972.

4. M. Levine, "Economical Analysis of Proposed Building Energy Performance

Standards," Lawrence Berkeley Laboratory Report PNL 3044, Sept. 1979.

5. C. Coblentz and P.R. Achenbach, "Field Measurements of Air Infiltration

in Ten Electrically Heated Houses." ASHRAE Transactions 69, 1963.

6. E. Stamper, "Weather Data," ASHRAE Journal, p. 47, Feb. 1977.

7. K. Kimura and D. G. Stephensen, "Solar Radiation on Cloudy Days,"

ASHRAE Transactions 75, Part I, pp. 227-233, 1969.
Table 1. Number of Hours During the Year When Temperature

Falls Within Various Temperature Bins

Temperature Bins*

col 1 col 2 col 3 col 4 col 5 Locations 65-71 72-77 78-82 above 82 above 72

Atlanta, GA 1878 1217 663 439 2319

Burbank, CA 1967 528 67 53 648

Chicago, IL 1102 717 330 275 1322

Fresno, CA 1087 745 526 1195 2466

Ft. Worth, TX 1117 1378 934 1422 3754

Houston, TX 1374 1808 1160 1244 4212

Minneapolis, MN 906 704 389 452 1545

Phoenix, AR 1157 900 718 2422 4040

Portland, OR 755 345 192 138 675

Washington, DC 1110 1008 601 722 2331

Percent

Possible whole- house-fan hours

col 2 + col 3 x 100

col 5

81%

92%

79%

52%

62%

70%

71%

40%

78%

69%

The bin data were generated from ASHRAE TRY (Test Reference Year) weather

data tapes.

Table 2. Annual Cooling Requirement of Hastings Ranch House With and

Without the Use of Whole-House Fan (WHF)

Control Mode #1 (Whole-house fan cycled by room thermostat)

Annual C ooling Estimated* Net Savings

kWh WHF Hours

of

Cooling

Savings

Fan Power

Consumption

Electri c Energy

Without With

Locations WHF WHF Operation kWh kWh kWh %

Atlanta, GA 3098 2056 288 1042 130 912 29.4

Burbank, CA 1870 1444 107 426 48 378 20.2

Chicago, IL 1725 1189 173 536 78 548 26.6

Fresno, CA 2845 2342 182 503 82 421 14.8

Ft. Worth TX 3894 2992 275 902 124 778 20.0

Houston, TX 4394 3172 361 1222 162 1068 24.1

Minneapolis, MN 1853 1332 162 521 73 448 24.2

Phoenix, AR 4580 4078 182 502 82 420 9.2

Portland, OR 1347 1025 90 322 41 281 20.9

Washington, 1 DC 2567 1859 201 708 90 618 24.1

* Assumed fan size 450 watt
Table 3. Annual Cooling Requirement of Hastings Ranch House With and

Without the Use of Whole-house Fan

Locations

Atlanta, GA

Burbank, CA

Chicago, IL

Fresno, CA

Ft. Worth, TX

Houston, TX

Minneapolis, MN

Phoenix, AR

Portland, OR

Washington, DC

Control Mode #2 (stepwise fan speed control)*

Annual Cooling Estimated* Net Savings

kWh WHF Hours Cooling Fan Power Electric Energy

Without With of Savings Consumption

WHF WHF Operation kWh kWh kWh %

3098 879

1870 961

1725 629

2845 1722

3894 2037

4394 1834

1853 755

4580 3356

1347 655

2567 1094

1880

595

1047

1271

2312

2968

1093

1618

537

1609

2219

909

1096

1123

1857

2560

1098

1224

692

1473

469

124

249

341

613

775

274

449

135

412

1750 56.4

785 42.0

847 49.1

782 27.5

1244 31.9

1785 40.6

824 44.5

775 16.9

554 41.3

1061 41.3

DB>82 air conditioner with no whole-house fan 0.6 AC/hr

82>DB>78 no air conditioner with whole-house fan 60 AC/hr

78>DB>72 no air conditioner with whole-house fan 30 AC/hr

72>DB natural ventilation, no air conditioner

and no whole-house fan, 6 AC/hr

when DB = outdoor temperature
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-0 1 ^v 83°F "^"

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-0 3 \82°F ^^^^

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— 80° f\ ^ 81°F \w

\ i >^ 1 •

I i 05 10 15 20 25 MS

100 ?00 300 400 500 m Ipm

AIR VELOCITY AROUND THE BODY

Figure 2. Fanger's comfort index with respect to

air speed around the body.

11
50

48

46

4442

40

38

x36

134

-32

%30

" : 28

+ 26

O WITHOUT WHF * WITH WHF

tfOUSE WHF BflS^LDG ATLANTA

DBVMflXr8*.flT

DBVMIN=65.0

Tl)L = 78.0

66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88

TEMPERATURE

89 90

Figure 3. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Atlanta, GA with and without the use of whole-house fan (WHF)

12
CD

50

48

46

44

42

40

38

36

34

32

dO

28

26

24

22

20

18

16

14

12

10

8

6

42

i r

' i i *r O WITHOUT WHF * WITH WHF

r " i i i r i r 1-

BEPS HOUSE WHF BASE BLOG BURBANK

0BVMAX=82.0

0BVMIN=65.0

TUL=78.0

5 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88

TEMPERATURE

89 90

Figure A. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Burbank, CA with and without the use of whole-house fan (WHF)

13
50

48

46

44

42

40 - 38

x36

?34

32

30

28

26

I O WITHOUT WHF * WITH WHF

HOUSE WHF BASE BLDG CHICAGO

" 0BVMAX=82.0

0BVMIN=65.0

66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86

J 87

!— J

TEMPERATURE

88 89 90

Figure 5. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Chicago, IL with and without the use of whole-house fan (WHF),

14
50

48

46

44

42

40

38

x36 - 134 - 32

30

28

26

i i

<D WITHOUT WHF * WITH WHF

BEPS HOUSE WHF BASE BLDG FRESNO

0BVMflX=82.0

DBVMIN=65.0

TUL=78.0

67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90

TEMPERATURE

Figure 6. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Fresno, CA with and without the use of whole-house fan (WHF),

15
50

48

46

44

42

40

38

z:36

134

32

30 h 28

26

-i r~ ~i r- —

,

, 1 i i i i 1 »——

i

r r" f r- r O WITHOUT WHF * WITH WHF

% 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87

TEMPERATURE

88 89 90

Figure 7. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Ft. Worth, TX with and without the use of whole-house fan (WHF),

16
50

48

46

44

42

40

38

x36

534

32

30

28

26 h

T" t I " " I ' ""I -I F I

' -l 1 1 1 r- O WITHOUT WHF * WITH WHF

%

BLDG HOUSTON

66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90

TEMPERATURE

Figure 8. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Houston, TX with and without the use the whole-house fan (WHF),

17
50

48

46

44

42

40

38

or 36

^34

32

30

* 28

26

£24

322

o20

5l8

ol6

Sl4

12

10

8

6

42

i

© WITHOUT WHF * WITH WHF

BEPS HOUSE WHF BASE BLOG MPLS

0BVMHX=82.0

0BVMIN=65.0

TUL=78.0

-M-m- 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90

TEMPERATURE

Figure 9. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Minneapolis, MN with and without the use of whole-house fan (WHF),

18
50

48

46

44

42

40

38

-I 1 1 1 * 1 1 I ' I 1 1 1 1~ l 1 1 r 1 1 1 1 1- O WITHOUT WHF * WITH WHF

BEPS HOUSE WHF BASE BLDG PHOENIX

0BVMAX=82.0

0BVMIN=65.0

TUL=78.0

>5 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90

TEMPERATURE

Figure 10. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Phoenix, AZ with and without the use of whole-house fan (WHF),

19
50

48 • 46 • 44

42 • 40 • 38

x36h

534

32

30

28

26

£24

322

o20

5l8

ol6

Sl4

12

10

8

6

42%

-i 1 r ——i 1 r—— r- © WITHOUT WHF * WITH WHF

-i 1 1 1 1 1 1 1 1 t 1 r i rHOUSE WHF BASE BLDG PORTLAND

0BVMflX=82.0

DBVMIN=65.0

TUL=78-0

66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88

TEMPERATURE

89 90

Figure 11. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Portland, OR with and without the use of whole-house fan (WHF).

20
50

48

46

44

42

40

38

n36

134

32

30

28

26

%

-I 1 r- -i 1 1 r 1 1 "— 1 1 r- O WITHOUT WHF * WITH WHF

BLDG WASHINGTON

5 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88

TEMPERATURE

89 90

Figure 12. Predicted daily total cooling energy consumption vs. daily

average outdoor temperature for a typical ranch house in

Washington, DC with and without the use of whole-house fan (WHF),

21
flTLRNTR

V)

8-1

8-

^

NDWf

LM-IC* pfnr

ez&%%444

0.0 0.2 0.4 0.6 0.B 1.0 1.2 1.4 1.6 1.8 PMV (PREDICTED MERN VOTE) AT CLO-1.0, V-0 M/S

2.0 2.2

I

1 1 1 1 "T 1 1 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

-I 1 1.6 1.8 PMV f PREDICTED MEAN VOTE) RT CLO-0.5, V-0 M/S

i 1

1

*

1 0.0 0.4 0.8 1.2 PMV (PREDICTED MEAN VOTE) RT CLO-0.5, V-0. 5 M/S

Figure 13. Predicted hourly frequency of comfort index in a typical ranch

house in Atlanta, GA with and without the use of whole-house fan

(WHF).

PMV=Fanger's Predicted Mean Vote

IMV=0 comfortable; PMV=1 slightly warm; PMV=2 warm.

22
BURBRNK

|-

|-

|i

8-

§-

9-

8

0.0 0.2

HHF

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.6 2.0 2.2 PMV (PREDICTED MEAN VOTE) AT CLO-1.0, V-0 M/S

I 1 1 1 1 :—

1 1 1 1 0.0 0.2 0.4 0.6 0.6 1.0 1.2 1.4 1.6 1.8 PMV (PREDICTED MEAN VOTE) AT CLO-0.5, V-0 M/S

i 1 r—

1 0.0 0.4 0.8 1.2 PMV (PREDICTED MEAN VOTE) AT CLO-0.5, V-0. 5 M/S

Figure 14. Predicted hourly frequency of comfort index in a typical ranch

house in Burbank, CA with and without the use of whole-house

fan (WHF).

IMV=Fanger's Predicted Mean Vote

PMV=0 comfortable; PMV=1 slightly warm; PMV=2 warm.

23
CHICAGO

8-

t 1 r t 1 r^NOMHF

HHF

o.o 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 PflV (PREDICTED HERN VOTE) RT CLO-1.0, V-0 li/S

i

1

1 i i———*i 1 1 1 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 PMV (PREDICTED MEAN VOTE) RT CLO-0.5, V-0 tt/S

i

1—~~—i— 1 0.0 0.4 0.8 1.2

2.2

1.8

PMV (PREDICTED HERN VOTE) RT CLO-0.5, V-0. 5 M/S

Figure 15. Predicted hourly frequency of comfort index in a typical ranch

house in Chicago, IL with and without the use of whole-house

fan (WHF).

PMV=Fanger's Predicted Mean Vote

PMV-0 comfortable; PMV=1 slightly warm; PMV=2 warm.

24
FRESNO

-i 1 1 1 1 1

i

1 r

1*

8-

8-

8-

^S3

.. JNOHHF

0.0 0.2 •n—

2.0 2.2

1.8

0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 PMV (PREDICTED MEAN VOTE) RT CLO-1.0, V-0 M/S

i

1 1 1 1 H 1 1 1

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 PMV (PREDICTED MEAN VOTE) AT CLO-0.5, V-0 M/S

i

1 1—4 1 0.0 0.4 0.8 1.2 PMV (PREDICTED MEAN VOTE) AT CLO-0.5, V-0. 5 M/S

Figure 16. Predicted hourly frequency of comfort index in a typical ranch

house in Fresno, CA with and without the use of whole-house

fan (WHF).

PMV=Fanger's Predicted Mean Vote

PMV=0 comfortable; PMV=1 slightly warm; PMV=2 warm.

25
FT. WORTH

to3§

77777,

NO HHf

HHF

o.o 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 PMV (PREDICTED HERN VOTE) AT CLO-1.0, V-0 M/S

i 1 1 1

1

;—*i 1 i 1 1 0.0 0.2 0.4 0.6 0.6 1.0 1.2 1.4 1.6 1.8 PMV (PREDICTED MEAN VOTE) AT CLO-0.5, V-0 M/S

0.0 0.4 0.8 1.2 PMV (PREDICTED MEAN VOTE) AT CLO-0.5, V-0. 5 M/S

Figure 17. Predicted hourly frequency of comfort index in a typical ranch

house in Ft. Worth, TX with and without the use of whole-house

fan (WHF).

PMV=Fanger's Predicted Mean Vote

MV=0 comfortable; MV=1 slightly warm; PMV=2 warm.

26
HOUSTON

|-

8-

|

§-

in§1-

x

8-

8-

8-

8-

0.0 -T—0.2

^NOWHF

HHF

0.4 0.6 0.6 1.0 1.2 1.4 1.6 1.8 2.0 2.2 PMV (PREDICTED MEAN VOTE) AT CLO-1.0, V-0 M/S

I 1 1 1 1 : T 1 1 1 I 0.0 0.2 0.4 0.6 0.6 1.0 1.2 1.4 1.6 1.8 PMV (PREDICTED MEAN VOTE) AT CLO-0.5. V-0 M/S

i

1———i— 1 0.0 0.4 0.8 1.2 PMV (PREDICTED MEAN VOTE) AT CLO-0.5, V-0. 5 M/S

Figure 18. Predicted hourly frequency of comfort index in a typical ranch

house in Houston, TX with and without the use of whole-house

fan (WHF).

PMV=Fanger's Predicted Mean Vote

PMV=0 comfortable; PMV=1 slightly warm; PMV=2 warm.

27
MINNEAPOLIS

t r t r Y///A N0 WHF

WHF

0.4 0.6 0.8 1.0 1.2 1.4 1.6 PMV (PREDICTED MEAN VOTE) AT CLO-1.0, V-0 M/S1.8 2.0 2,2

I 1 i 1 i " i 1 i 1 i 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 PMV (PREDICTED MEAN VOTE) AT CL0-0.5, V-0 M/S

i 1

1

1 0.0 0.4 0.8 1.2 PMV (PREDICTED MEAN VOTE) AT CLO-0.5, V-0. 5 M/S

Figure 19. Predicted hourly frequency of comfort index in a typical ranch

house in Minneapolis, MN with and without the use of whole-house

fan (WHF).

PMV=Fanger's Predicted Mean Vote

PMV=0 comfortable; PMV=1 slightly warm; PMV=2 warm.

28
PHOENIX

Sit 1 1 1 1 r i i ^3 NO WHF

HHF

zzzz:

0.0 0.2 =F

0.4 0.6 0.B 1.0 1.2 1.4 1.6 1.8 PMV (PREDICTED MERN VOTE) AT CLO-1.0, V-0 M/S

i 1 1 1 1 'i i 0.0 0.2 0.4 0.6 0.6 1.0 1.2

2.0 2.2 T 1 I 1.4 1.6 1.8 PMV t PREDICTED MERN VOTE) RT CLQ-0.5, V-0 M/S

I

1

' r~* 1 0.0 0.4 0.8 1.2 PMV t PREDICTED MERN VOTE) RT CLO-0.5, V-0. 5 M/S

Figure 20. Predicted hourly frequency of comfort index in a typical ranch

house in PJioenix, A2 with and without the use of whole-house

fan (WHF).

PMV=Fanger's Predicted Mean Vote

mv=0 comfortable; PMV=1 slightly warm; PMV-2 warm.

29
PORTLRND

t 1 1 1 1 r t r

1-

IV///A TM WHF

HHF

2.0 2.2 —i

1.6 -1.8

0.4 0.6 0.6 1.0 1.2 1.4 1.6 1.8 PMV (PREDICTED MEAN VOTE) AT CLO-1.0, V-0 M/S

| 1 1 ! 1 —*T 1 1 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 PMV f PREDICTED MEAN VOTE) AT CLO-0.5, V-0 M/S

i

1 r—*

1 0.0 0.4 0.8 1.2 PMV f PREDICTED MEAN VOTE) AT CLO-0.5, V-0. 5 M/S

Figure 21. Predicted hourly frequency of comfort index in a typical ranch

house in Portland, OR with and without the use of whole-house

fan (WHF).

PMV=Fanger's Predicted Mean Vote

PMV=0 comfortable; fflV=l slightly warm; PMV=2 warm.

30
WASHINGTON

§-1

8

8-

t 1 1 r t 1 1 r ^^NOHHF

1 HHF

&o.ow??WK 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.6 PMV (PREDICTED MEAN VOTE) AT CLO-l.O, V-0 M/S

2.0 2.2

l

1 1 1

1 *i

1 f—

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

-l 1 1.6 1.8 PMV (PREDICTED MEAN VOTE) FIT CLO-0.5, V- M/S

i 1 —i— 1 0.0 0.4 0.8 1.2 PMV (PREDICTED MEAN VOTE) AT CLO-0.5, V-0. 5 M/S

Figure 22. Predicted hourly frequency of comfort index in a typical ranch

house in Washington, DC with and without the use of whole-house

fan (WHF).

PMV=Fanger's Predicted Mean Vote

PMV=0 comfortable; PMV=1 slightly warm; PMV=2 warm.

31
400Q

3000

<s

o

PS

CO

2000 -

1000

J L 70

T 1 1 1 1 1 1 1 I

Washington, DC Ranch House

Cooling kWh of the no whole house fan house

Cooling kWh + fan kWh

for whole house fan house

J I L J I I L

75 80

INDOOR TEMPERATURE, °F

85

Figure 23. Annual cooling kWh vs indoor thermostat settings in a Washington D.C. ranch house.

32
80

70

CO

CO

50 -

40 -

30

20

10 -

1 1 1 1 l l I i I

-

Atlanta / ~

- Chicago /

Minneapolis• // Burbank -

Washington #*X 9

• /Houston Portland

-

Fresno >^ Ft Worth

—

Phoenix *

yS —

1

1 1 ' 1 1 1 1 1 10 20 30 40 50 60 70

% OF POSSIBLE WHOLE-HOUSE FAN HOURS

80 90 100

Figure 24. Cooling kWh savings vs percent of possible whole-house fan

hours.

33
NBS-114A IREV. 2-8C) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO. NBS TN 1138

2. Performing Organ. Report No 3. Publication Date

May 1981

4. TITLE AND SUBTITLE

Savings in Electric Cooling Energy by the Use of a Whole-House Fan

5. AUTHOR'S)

T. Kusuda and J.W. Bean

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered Final

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

Same as above.

10. SUPPLEMENTARY NOTES

]] Document describes a computer program; SF-185, FlPS Software Summary, is attached.

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

bibliography or literature survey, mention it here)

Hour-by-hour cooling performances of a typical ranch house, with and without the use of a whole-house fan, were compared for the climate conditions throughout

the contiguous United States. The comparative analyses were made by the use of

NBSWHF, a modified version of NBSLD, to simulate the complex thermal coupling

of whole-house-fan ventilated attic space. The calculations were performed for

two operational modes: a cyclic fan mode and a stepwise continuous mode.

The calculation predicted a large cooling energy savings as compared to the

house without the use of the whole-house fan, without significant deterioration

of indoor thermal comfort.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

building thermal performance; energy calculation; energy conservation; thermal

comfort; whole-house ventilation

13. AVAILABILITY

|"X~| Unlimited

~2 For Official Distribution. Do Not Release to NTIS

r_TJ ^

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402. H Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

39

15. Price

$2.75

USCOMM-DC 6043-P80

-fr US. GOVERNMENT PRINTING OFFICE : 1981 O—340-997 (1643)
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