NAT L INST. OF STAND & TECH

NIST

PUBLICATIONS

NBSIR 76-1088

Estimating the Energy

Conservation Potential of

Ventilation Control Through

Weather Data Analysis

T. Kusuda and J. W. Bean

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D C. 20234

August 1977

Final

Prepared for Federal Energy Administration

New Post Office Building

1 2th and Pennsylvania Avenue

Washington, D.C. 20461

NBSIR 76-1088

ESTIMATING THE ENERGY

CONSERVATION POTENTIAL OF

VENTILATION CONTROL THROUGH

WEATHER DATA ANALYSIS

T. Kusuda and J. W Bean

Thermal Engineering Section

Building Environment Division

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

August 1977

Final

Prepared for Federal Energy Adnninistration

New Post Office Building

12th and Pennsylvania Avenue

Washington, D.C. 20461

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

ESTIMATING THE ENERGY CONSERVATION POTENTIAL OF

VENTILATION CONTROL THROUGH WEATHER DATA ANALYSIS

by

T. Kusuda and J. W. Bean

ABSTRACT

Hourly weather data for six selected cities in the United States covering eleven

consecutive years were analyzed to aid in estimating the possible energy saving that could

be achieved by closing the outdoor dampers during unoccupied hours. The analysis shows

that, depending upon the local weather condition, and with some simplifying assumptions,

from 74 to 83 percent of the energy used for heating the make-up air could potentially be

saved by closing the outdoor dampers when the building is not occupied. Based upon a premise that the energy required for cooling the outdoor ventilation air is proportional

to the average enthalpy difference between the outdoor air and the air leaving the cooling

coll, from 53 to 63 percent of the energy for cooling of ventilation air could be saved

by closing the outdoor dampers during unoccupied hours.

Hourly temperature and enthalpy values are presented in histogram form for occupied

and unoccupied periods (office use), with the suggestion that similar data processing

be carried out for other cities as well.

Key Words: Air conditioning requirements; energy conservation; intermittent ventilation;

ventilation control; weather data analysis.

1. INTRODUCTION

Recent studies conducted by the National Bureau of Standards indicate that the heating

and cooling of outdoor air needed for commercial building ventilation is a major component

of heating and cooling energy requirements for a given building [1, 2]*. For example,

75 percent of the average fuel oil consumed by 19 New York City schools was used to heat

the ventilation air. The critical evaluation of the real requirements of ventilation air

from the standpoint of the occupants' health, thermal comfort, and the quality of indoor

air merits attention in order to minimize the excess use of outdoor air and hence conserve

energy [3]. On the other hand, it is now possible to reduce the requirements for mechanical

cooling by taking advantage of cool outdoor air for cooling where possible.

For the sake of energy conservation, the following should be considered:

1. When the ventilating air is either heated or cooled, the quantity of outdoor air

should be minimized to the point really necessary for maintaining indoor air quality and

the occupants' comfort and health.

2. The use of outdoor air for "natural" cooling should be maximized during the

non-heating season.

3. Energy should be recovered from the exhaust air wherever possible by the use of

heat exchangers.

* Numbers in brackets indicate references at end of text.

1
Although each of these considerations merits separate and detailed analysis depending

upon the specific application, the attention of this report will be directed toward one

of the simplest steps: closing outdoor air dampers during unoccupied periods.

2. ENERGY SAVING BY CLOSING THE OUTDOOR AIR DAMPERS DURING UNOCCUPIED PERIODS

The energy saving as a result of closing the outdoor ventilation dampers during the

unoccupied periods was analyzed as described below. Detailed hourly mechanical system

simulation calculations by the use of computer revealed that the heating requirement Qu

for processing the ventilation air can be approximated by a linear function of the

difference between the indoor temperature t^ and outdoor temperature t^.

Qr = ^ <4 -

^o)

In this equation, a is a proportionality constant which depends on the amount of total

ventilation air and the efficiency of the heating system used in a given building.

Let = the annual energy consumption for heating of ventilation air when the

outdoor air damper is open continuously

and Qp = the annual energy consumption for heating of ventilation air when outdoor

ventilation is on only during the occupied periods.

Then = a Z (t, - t^)^^ • ^2) total

Q = a E (t^ - t^)-/ (3)

occupied hours

The following energy saving factor V]^ can be used as a measure of the energy saving

due to shutting down the ventilation system during the unoccupied periods:

n„ = ^ X ICQ (4)

*o T (t. - t ) or ^ ^ ° unoccupied ^

total

In the equations (2) through (5) , 2 signifies the summation over an entire year

for hours when:

"i ^

*7 — No distinction is made at this point for the notations between the in and outdoor

temperatures during the occupied and unoccupied periods.

2
Equation (5) may be modified as:

t

.

1 = the average indoor temperature during the heating season

t.1 = the average indoor temperature during the unoccupied period

t

' o = the average outdoor temperature during the unoccupied hours

t o

= The average outdoor temperature during the heating season

N' = the number of hours during the heating season when the building

is unoccupied

N = the total numberof hours during the heating season.

In order to evaluate rirrj it is only necessary to know the average indoor and outdoor

air temperatures during the neating season during the unoccupied hours of the same time

period, since the values of N' and N can be very easily determined. While the average

outdoor air temperature ("t ) during the heating season may be available or estimated from

monthly degree-day data, tfie average outdoor temperature during the unoccupied period of

the heating season has not been compiled, to the best of the authors' knowledge.

*/ Figures 1 through 3 were prepared to compare the monthly average temperature for

three periods in a day: hour 1 through hour 8, hour 9 through hour 16, and hour 17 through

hour 24 for Concord, New Hampshire; Washington, D. C.,' and Orlando, Florida, respectively.

These figures show that the average temperatures during the occupied hours (9-16) are considerably different from those during the non-occupied hours (1-8 and 17-24) in Concord,

New Hampshire; however, the differences are smaller in the southern cities. For the sake

of interest, similar plots were made for the outdoor dewpoint temperature for the same cities and are shown in Figures 4 through 6. These latter figures show that there is no significant difference in dewpoint temperature between the occupied and unoccupied periods.

In those localities where the daily average outdoor temperature, "t , is very nearly

the same as the average outdoor temperature during the unoccupied periods, t" ', the

energy-saving factor rijj can be calculated simply by knowing the occupied hours during the

season, and by the indoor temperatures during the occupied and unoccupied periods.

If one assumes that the heating season consists of all the non-summer months (September

through March) and the working hours are from 8 a.m. to 5 p.m. of 147 working days, the

total occupied heating hours will be 1323, whereas the total heating hours will be 5088

(212 days) , including Saturdays, Sundays, and holidays. The value for r\-^ can thus be written

as

:

Figures are grouped at end of text,
(5088 - 1323) t. • + 1323 t,"

, — 1 i

where t . =

^ . 5088

and = average indoor temperature during the occupied hours,

Equation (7) shows that the percent savings for the heating of ventilation air is

74 percent when the average indoor temperature and the average outdoor temperature remain

constant throughout the occupied and unoccupied periods. The percentage savings tends to

increase when the unoccupied period has a lower average outdoor temperature. The value of

rijj is also affected by the level of indoor temperature, since for a given outdoor temperature

depression during the unoccupied period, as compared to the average outdoor temperature for

the season, the percentage savings becomes higher for the location when the annual average

value of Tq is closer to the indoor temperature.

Calculation of this type of data can be made easier and more accurate if statistical

data for the hourly outdoor temperature are available for the occupied and non-occupied

hours separately. It would also be helpful if data were available to analyze the potential

of using natural cooling instead of air conditioning during the cooler night hours of the summer months, reserving air conditioning for those periods when the building is occupied,

and the outside air is warm.

3. ANALYSIS OF WEATHER DATA

In order to demonstrate a possible energy saving through the proper use and schedule

of ventilation air, hourly weather data for six selected cities were analyzed as follows:

(a) Hourly frequency histograms of dry-bulb temperature for the occupied and

non-occupied periods as well as for the total year were first constructed for eleven

consecutive years for Washington, D. C. , covering 1954 through 1964. The results are shown in Figures 7 through 17. The shapes of the histograms vary considerably from year

to year. Indicated in the upper righthand corner of these figures are three indices which

are developed from the histogram, termed "heating degree hours" (HTGDH) ; cooling degree

hours (CLGDH) ; and cooling enthalpy hours (CLGEH) . The definitions of these quantities

are as follows:

HTGDH = E(7o -

CLGDH = 75)

CLGEH 24)

The definitions of these degree hours are such that the summation for the above

equations was carried out only for the periods when the values in the parentheses were

positive. The quantity "24" in CLGEH is the enthalpy value of moist air corresponding to

the dewpoint temperature of 56° F (13. 3°C) , which is the apparatus dewpoii.n temperature of

typical air-cooling systems. This value was used instead of the indoor air enthalpy because

the outdoor air is usually cooled down to the apparatus dewpoint temperature first.*

Table 1 lists the year-to-year variations of HTGDH, CLGDH and CLGEH, as well as the percent

of these values, for the unoccupied period for Washington, D. C. , during 1954-1964. When

it is assumed that the indoor temperatures for occupied and unoccupied hours are the same during the heating season, these values represent rijj, the ventilation energy saving factor.

For the purpose of this analysis, it has been assumed that the energy required for cooling

ventilation is proportional to the cooling enthalpy hours (CLGEH) . Based on this assumption,

the energy saving due to shutting off the outdoor ventilation air during unoccupied hours

This assumption is also consistent with the other assumption that the cooling system

operates under an assumed and constant coefficient of performance representing an average

value of the cooling season.

k
in the summer season would be equal to the fraction of the total cooling enthalpy hours that

occurred during the unoccupied hours.

As can be seen from Table 1, the heating degree hours (HTGDH) and the corresponding

energy saving factors are very consistent throughout the 11-year period with spreads of

13 and 3 percent, respectively. Cooling degree hours (CLGDH) and cooling enthalpy hours

(CLGEH) , however, vary widely from year to year, represented by the spread of 41 and 86

percent, respectively. The energy saving factors for ventilation air cooling varied much

less during the same period (15 and 14 percent, respectively).

Table 1

Washington, D. C. Hourly Weather Data Summary

HTGDH CLGDH CLGEH

Year

1954

1955

1956

1957

1958

1959

1960

1961

1962

1963

1964

Total r]^

134104 75

138690 74

141990 75

133908 74

149174 74

129606 73

144260 74

142330 74

147410 73

148116 74

137706 74

Total

10999

10264

7662

11271

7216

13313

9048

10189

8611

9436

10640

53

53

55

59

55

56

56

52

53

51

54

Total

18050

21112

14488

28755

11110

39410

18971

26840

14119

17559

14728

\

41

62

62

65

59

67

61

64

58

62

61

Average 140663

Spread 18510

% Spread 13

74 9877 55 20495 63

2 4055 8 17645 9

3 41 15 86 14

* percentage of degree hours during the unoccupied period (5 p.m. - 8 a.m.)

which is the "energy saving factor."

Key: minimum

maximum

5
(b) The hourly weather data analysis for the ten-year period was performed for other

cities (Orlando, Florida; Concord, New Hampshire; Phoenix, Arizona; Omaha, Nebraska; and

Newark, New Jersey) to examine how the histograms, as well as the ten-year average values

for HTGDH, CLGDH and CLGEH, varied from city to city. Figures 18 through 23 depict the

ten-year average annual hourly frequency of outdoor temperature, whereas Figures 24 through

29 depict the same for the outdoor air enthalpy. Shown in each of these figures are the

histograms for occupied hours, non-occupied hours and total hours. It is interesting to

note that except for Phoenix and Orlando, the temperature histograms show two distinct

peaks.

Compared with the temperature profiles, enthalpy-frequency profiles are much more

irregular, especially in the enthalpy range of 20-35 Btu/lb., which is very surprising

if one considers that these figures represent the ten-year averages. It is unclear at the

moment why the enthalpy histograms show such fluctuations.

Table 2 shows the ten-year average values of the heating degree hours, cooling degree

hours, and cooling enthalpy hours for these six cities. Although these values vary con- siderably from city to city because of the difference in their climatic conditions, the

energy-saving factors are relatively consistent among the cities.

Table 2. Average* of Hourly Weather Data Summary for Six Selected Cities

HTGDH CLGDH CLGEH

Total

%

Unoccupied Total

%

Unoccupied Total

%

Unoccupied

Washington, D. C. 140663 74 9877 55 20495 63

Orlando, Florida 35551 83 21286 45 51331 61

Concord, New Hampshire 216855 75 4225 45 8402 54

Phoenix, Arizona 65560 80 47902 59 15312 59

Omaha, Nebraska 187778 74 10714 56 12977 61

Newark, New Jersey 157264 75 7111 49 14693 59

Washington and Concord were calculated from 11-year data,

TABULATION OF THE HOURLY FREQUENCIES OF DRY-BULB TEMPERATURE AND ENTHALPY

The histogram of hourly outdoor temperature and enthalpy for the occupied and nonoccupied periods is useful in observing the general profile. Tabulated data which are represented in these histograms are also needed, however, especially for the "bin" method

of energy consumption an^],ysis when the heating and cooling loads are calculated for each

of the temperature bins [^]. Tables 3 through 14 have thus been included in this report to

provide this information. These tables are grouped together following Section 6.

6
5. SUMMARY AND DISCUSSION

It was pointed out in this paper that the energy consumption for the heating and

cooling of ventilation air can be a significant part of the overall building energy usage,

and it is strongly influenced by the hourly outdoor dry-bulb temperature and enthalpy value.

By cutting off all make-up air during unoccupied heating hours, it is possible to decrease

the energy used to heat the outdoor air from 74 to 83 percent; depending upon the climatic

region.

The corresponding saving for cooling the make-up air could be from 54 to 63 percent^

depending upon the weather conditions of the region under consideration. These figures

are, however, obtained on the assumption that the indoor conditions were maintained at

the same levels during occupied and unoccupied hours. Also, no consideration has been

given to the fact that the ventilation rate may be regulated in accordance with the need

of specific spaces even during the occupied period. Although more extensive studies are needed to account for these aspects of the hour-by-hour simulation of the ventilation system,

the data presented herein provide firsthand estimates for the potential energy saving by

shutting off the make-up air supply system during unoccupied periods. The magnitude of

the possible energy saving obtained by this sort of ventilation control can be estimated

from the histogram data of hourly dry-bulb temperature and enthalpy for occupied and

non-occupied periods. This paper presents such data for six selected cities in both

tabular and graphical forms. Data of this type should be developed for most of the major

cities in the United States, because they are not only useful for estimating possible

energy savings by controlling ventilation air, but also for other purposes such as in the

"bin" method of annual energy calculations for buildings. The findings of this paper

indicate the value of increased research and hardware development activities in the area

of ventilation system controls.

6. REFERENCES

1. Hoffman, J. D. , at al. Energy Conservation at the NBS Laboratories, NBSIR 7^-539,

U.S. Department of Commerce, National Bureau of Standards (July 197^).

2. Liu, S. T. , C. M. Hunt and F. J. Powell, Evaluation of Ventilation Requirements

and Energy Consumption in Existing New York City School Buildings, National Bureau

of Standards Building Science Series, BSS 97 (April 1977).

3. Energy Conservation Guidelines for Existing Office Buildings (Feb 1975), and Energy

Conservation Guidelines for New Office Buildings (July 1975), both by General

Services Administration, Public Buildings Service, Washington, D.C. 20U05.

k. Energy Estimating Methods, Chapter h3, ASHRAE Handbook & Product Directory, 1976,

Systems , pp. U3.1-i+3.l8, American Society for Heating, Refrigerating and AirConditioning Engineers, Inc.

7

Table 3. Average Hourly Frequencies of Outdoor Temperature for Occupied

and Unoccupied Periods for Phoenix, Arizona

Outdoor Occupied Hours Unoccupied Hours

Temperature, °F Per Year Per Year Total

18. 0. 0. 1.

20. 0. 1. 1.

22. 1. 1. 1.

24. 0. 1. 2.

26. 1. 3. 4.

28. 2. 10. 12.

30. 3. 19. 22.

32. 5. 26. 31.

34. 8. 34. 42.

36. 13. 57. 70.

38. 16. 77. 93.

40. 23. 106. 129.

42. 28. 150. 178.

44. 32. 157. 189.

46. 39. 170. 210.

48. 46. 210. 257.

50. 47. 202. 249.

52. 54. 215. 269.

54. 63. 235

.

298.

56. 69

.

223. 292

.

58. 70. 231. 301.

60. 82. 223. 305.

62. 77. 214. 291.

64. 82. 216. 298.

66. 86. 213. 299

.

68. 90. 215. 305

70. 90. 221. 311.

72. 89. 219

.

307.

74. 87. 217. 305.

76. 91. 232. 323.

78. 86. 235. 321.

80. 101. 224. 325.

82. 92. 225. 317.

84. 100. 212. 312,

86. 91. 181. 272.

88. 91. 163. 254.

90. 99. 151. 249.

92. oft. 136. 234.

94. 94. 121. 215.

96. 93. 122. 215.

98. 88. 102

.

190.

100. 69 84 -L J • 102. 56. 65 122

,

104. 41 47 88.

106. 24. 28. 53.

108. 14. 16. 30.

110. 6. 7 13

.

112. 2. 1. 3. 114. 1. 0. 1.

116. 0. 0. 1.

TOTAL 2542. 6222.

* 8765.

Due to roundlng-off arithmetics, the total hours may not exactly match the sum of occupied and unoccupied hours.

**The average total number of hours would vary from 8765 to 8767 depending upon

the number of leap years included in the calculation period.
Table 4. Average Hourly Frequencies of Outdoor Air Enthalpy for Occupied

and Unoccupied Periods for Phoenix, Arizona

Outdoor Air Occupied Hours Unoccupied Hours

Enthalpy, Btu/lb Per Year Per Year Total

n\J • X1 • 1.

7 ^1 • 2 3. « 1X • 6.

Q 22 26.

1 0 ^ • 27 32

.

11. 1 3 53 65.

1 2 21^ X • Q3 113.

J / o 36 X1 41*-r X • 177.

60 260 319

J / • 246 302.

71/ X • ^ O X • 352

17

.

/ • 424

1 9 486

19. Xw1 27/ .JX '^^ 7/ • 445

20 92 274 366.

21 1 ft? AOO 563

22 171 ov ^ . 563

2"^ QO 1 QD 280

1 sn jD^ . 549

2S Q9 X171/ X . 963

• iH1 ARo • mo AS7

9 7 7A/ D . Xlo . 99A

^ o • X J J • 9 "^Q '^7A 9Q-7 • ASoo

.

997

'^0 ft7 1 9 x^1 Q9z.

.

'^1 xto 1 Aft . 9 "^7 Z J / . O J . Z917X / . JUX .

_)-) . X J J . xoo 1 88 • S7 X1 AQH !7 . 206

• 67 X1 ftA U H • 232

J u * 71/ X . XDH 1 AA . z935 . 7 DO . 1 JJ . ZUZ 9n9 . 38. 69. 98. 168.

39. 52. 66. 118.

40. 27. 29. 56.

41. 8. 7. 15.

42. 1. 1. 2.

43. 1. 1. 1. 46. 0. 0. 1.

TOTAL 2542. 6223. 8765.*

*The average total number of hours would vary from 8765 to 8767 depending on the

number of leap years included in the calculation period.
Table 5. Average Hourly Frequencies of Outdoor Temperature for Occupied

and Unoccupied Periods for Concord, New Hampshire

Outdoor Occupied Hours

Temperature. *F Per Year

-26. 0. -24. 0. -22. 0. -20. 0. -18. 1. -16. 0. -14. 1. -12. 1. -10. 1. - 8. 1. - 6. 2. - 4. 3. - 2. 5.

0. 4. 2. 5.

4. 7.

6. 9.

8. 10.

10. 11.

12. 15.

14. 20.

16. 23.

18. 27.

20. 35.

22. 39.

24. 49.

26. 53.

28. 63.

30. 71.

32. 88.

34. 87.

36. 86.

38. 79.

40. 74.

42. 79.

44. 77.

46. 71.

48. 71.

50. 69.

52. 73. 54. 70.

56. 79.

58. 76.

60. 85.

62. 81.

64. 88.

66. 77.

68. 83.

70. 79.

72. 77.

74. 77.

76. 66.

78. 63.

80. 60.

82. 51.

84. 44.

86. 26.

88. 20.

90. 13.

92. 7. 94. 5. 96. 3. 98. 1. TAL 2542.

Unoccupied Hours ^ Per Year Total

0. 1.

1. 1.

1. 1.

1. 1.

2. 3.

2. 3.

3. 3. 5. 6.

4. 4. 10. 11.

13. 14.

14. 17.

16. 21.

15. 19.

21. 26.

31. 38.

35. 43.

44. 54.

52. 63.

63. 78.

69. 89.

84. 107.

94. 121.

122. 157.

140. 179.

171. 220.

183. 236.

216. 278.

242. 313.

262. 350.

248. 335.

i25. 311.

203. 283.

201. 276.

208. 286.

206. 283.

205. 276.

198. 269.

208. 277.

210. 283.

200. 270.

216. 295.

207. 282.

210. 295.

199. 280.

185. 273.

174. 252.

156. 239.

136. 215.

110. 187.

90. 167.

72. 137.

61. 123.

53. 113.

40. 91.

29. 73.

^ J. 49

17. 36. 12. 25.

6. 13.

3. 8. 1. 3. 0. 1. 6225. 8767.*

The average total number of hours would vary from 8765 to 8767 depending upon the

number of leap years included in the calculation period.
Table 6. Average Hourly Frequencies of Outdoor Air Enthalpy for Occupied

and Unoccupied Periods for Concord, New Hampsire

Outdoor Air Occupied Hours Unoccupied Hours

Enthalpy, Bt:u/lb Per Year Per Year Total

- 5. 1. 2. 3. - 4. 1. 4. 5.

1. 8. 9. - 2. 2. 16. 18.

- 1. 4. 25. 29.

0. 8. 28. 36.

1. 10. 38. 48.

2. 17. 69. 86.

3. 20. 82. 103.

4. 28. 99. 127.

5. 38. 134. 172.

6. 56. 176. 232.

7. 79. 234. 313.

8. 69. 246. 315.

9. 96. 274. 371.

10, 94. 310. 405.

11. 132. 322. 455.

12. 108. 306. 413.

13. 132. 323. 455.

14. 93. 201. 294.

15. 91. 218. 309.

16. 92

.

225. 317.

17. 89 229 318.

18. 86. 219 305.

19. 88 213 301.

20. 93 ?1 9 312

.

21 70 X JO • 208.

22 X^ J • 266

23 1 no xo • 318.

24. -jy • X J J • 192

25. 1 07 £^ m 328.

26. 60 1 "^0 190

27 1 01 X71 QRo

.

299

28 X110X\J • 165

29 • XVJ 1 07/ • 1 60

30 ox • XD X . 31 Q7 X1 -J"iOw • 32 HX • 79 XX113J • 33. 41. 58. 99.

34. 44. , 63. 106.

JJ

.

jU . HO . / D . 36. 20. 24.

• 44.

37. 13. 14. 27.

38. 7. 9. 15.

39. 5. 5. 10.

40. 2. 1. . 3.

41. 1. 0. , 1.

TOTAL 2541 6224 8765*

*The average total number of hours would vary from 8765 to 8767, depending upon the

number of leap years included in the calculation period.
Table 7. Average Hourly Frequencies of Outdoor Temperature for Occupied

and Unoccupied Periods for Newark, New Jersey

Outdoor Occupied Hours

Temperature, °F Per Year

0. 0.

2

.

0.

4. 1.

6. 1.

8. 1.

10. 3.

12. 4.

14. 5.

16. 8.

1 o 18. 11.

20. 12.

22. 16.

24. 21.

25. 29.

o o 2o. 36.

JO. 49.

o o JZ

.

64.

34. 81.

36. 84.

38. 88.

40. 90.

42. 84.

44. 89.

46. 83.

48. 79.

50. 78.

52. 78.

54. 79.

56. 74.

58. 77.

60. 83.

62. 83.

64. 86.

66. 86.

68. 95.

70. 96.

72. 87.

74. 90.

76. 91.

78. 85.

80. 81.

82. 66.

OH . _)Z

.

86. 45.

88. 32.

90. 24.

92. 16.

94. 9.

96. 5.

98. 4.

100. 2.

TOTAL 2542

* Due to rounding-off arithmetics, the total

occupied and unoccupied hours.

* The average total number of hours would va number of leap years included in the calcu:

Unoccupied Hours

Per Year Total

0. 1.

0. 1.

1. 1.

5. 7. 4. 5.

6. 9.

10. 14.

22. 27.

28. 36.

36. 47.

43. 55.

63. 79.

83. 104.

100. 129.

126. 162.

166. 214.

204. 268.

237. 318.

261. 345.

260. 348.

235. 324.

222. 306.

235. 324.

208. 291.

194. 273.

204. 282.

212. 290.

210. 288.

218. 292.

213. 290.

226. 308.

230. 313.

232. 318.

224. 309

.

245. 340.

230. 326.

232. 319

.

209. 298

149. 240.

120. 206.

89. 170.

71. 137

.

50. 103.

37. 82.

24. 56.

17. 41.

13. 29.

8. 17.

5. 10.

3. 7. 1. 3.

6222 8765*

hours may not exactly match the sum of

y from 8765 to 8767, depending upon the

ation period.
Table 8. Average Hourly Frequencies of Outdoor Air Enthalpy for

Ocqupied and Unoccupied Periods for Newark, N. J.

Outdoor Air Occupie4 Hours Unoccupied Hours

Enthalpy, Btu/lb . Per Year Per Year Total

1. 1. 1. 2.

2. 2. 8. 11.

3. 5. 11. 16.

4. 8. 31. 39.

5. 15. 55. 69.

6. 26. 78. 103.

7. 36. 123. 159.

8. 43. 151. 195.

9. 66. 202. 268.

10. 78. 251. 329.

11. 118. 305. 423.

12. 137. 372. 509.

13. 118. 300. 418.

14. 102. 251. 353.

15. 95. 235. 331.

16. 96. 232. 329.

17. 93. 219. 312.

18. 84. 221. 306.

19. : 93. 228. 321.

20. 97. . 230. 326.

21r 88. 220. 309.

22. 64. 134. 197.

23. 101. 223. 325.

24. 86. 189. 274.

25. 70. 193. 263.

26. 91. 186. 277.

27. 82. 214. 296.

28. 62, 135. 196.

29. 103. 232. 335.

30. 57. 146. 204.

31. 49. 110. 159.

32. 62. 128. 189.

33. 78. 180. 258.

34. 52. 127. 178.

35. 45. 98. 143.

36. 40. 68. 109.

if. 31. 62

.

9 J

.

38. 30. 36. 66.

39. 19. 21. 39.

40. 12. 9. 21.

41. 4. 3. 8.

42. 1. • ii 3.

43. 1. 1.

44. 0. 0. 1.

TOTALS 2542 6223 8765

The average to^ial number of hours wpuld vary from 8765 to 8767 depending upon the

number of leap years included in the calculation period.
Table 9. Average Hourly Frequencies of Outdoor Temperature for Occupied

and Unoccupied Periods for Washington, D. C.

Outdoor Occupied Hours Unoccupied Hours

Temperature, °F Per Year Per Year Total

6. 1. 1.

-I1.

8. 1. 1. 2

.

10. 2. 6.

-7/ . 12. 4. 10.

14. 5. 14. ly

.

16. 6. 1 O 18. Zh . 18. 10. 31.

20. IJ. 4/ . bU

.

1 o lo. o2.

.

l\j

.

24. zl. b /

.

0 / . 26. yi

.

28. 32. 106

.

13/

.

30. 46. 145

.

191

.

32. 58. 194. 251.

34. 62. 199. o o 262

.

36. 77. 215. ; O o 293.

38. 82. 227

.

r\r\ 309

.

40. 78. 217. 295.

42. 83. 223. 306.

44. 77. 211. 287.

46. 73. 199. 272

.

48. 76. 181. 257.

50. 67. 197. 264.

52. 76. 186. 263.

54. 71. 181. 253.

56. 73. 190. 263.

58. 71. 179. 250.

60. 78. 198. 276.

62. 88. 226. 314.

64. 79. 211. 290.

66. 83. 231. 314.

68. 84. 235. 318.

70. 98. 269. 367.

72. 102. 287. 389.

74. 108. 274. 382.

76. 99. 214. 313.

78. 84. 165. 249.

80. 91. 148. 238.

82. 81. 117. 198.

84. 74. 94. 168.

86. 61. 65. 127.

88. 54. 42. 96.

90. 35. 31. 66.

92. 20. 19. 39.

94. 6. 7. 12.

96. 3. 3. 6.

98. 2. 1. 3.

TOTAL 2543. 6223. 8767.'

* Due to rounding-off arithmetics, the total hours may not exactly match the sum of

occupied and unoccupied hours.

** The average total number of hours would vary from 8765 to 8767 depending upon the

number of leap years included in the calculation period.
Table 10. Average Hourly Frequencies of Outdoor Air Enthalpy for

Occupied and Unoccupied Periods for Washington, D. C.

Occupied Hours Unoccupied Hours

Enthalpy, Btu/lb Per Year Per Year Total

1. 0. 0. 1.

2. 1. 3. 4.

3. 4. 15

.

19.

4. 7. 22. 30.

5. 15. 39

.

54.

6. 24. 79. 103.

7. 41. 110. 151.

8, 43. 132. 175.

9. 58. 169. 227.

10. 66. 229. 295.

11. 114. 306. 420.

12. 127. 356. 483.

13. 106. 266. 372.

14. 96. 237. 333.

15. 92. 220. 312.

10. 94. 230. 324.

17. 86. 203. 289.

18. 92. 194. 286.

19. 81. 187. 268.

20. 83. 201. 284.

21. 74. 181. 255.

22. 50. 123. 174.

23. 86. 208. 294.

24. 78. 162. 240.

25. 63. 166. 229.

26. 81. 169. 250.

27. 83. 217. 300.

28. 71. 158. 229.

29. 101. 258. 358.

30. 57. 164. 221.

31. 52. 131. 182.

32. 70. 142. 211.

33. 104. 229. 333.

34. 78. 187. 265.

35. 62. 152. 214.

36. 56. 122. 178.

37, 44. 96. 140.

38. 45. 73. 118.

39. 29. 41. 70.

17 ^ • A?

41. 7. 13. 20.

42. 3. 6. 8.

43. 1. 2. 3.

44. 1. 1. 2.

45. 0. 1. 1.

TOTAL 2543. 6224. 8767.

* The average total number of hours would vary from 8765 to 8767 depending upon the

number of leap years included in the calculation period.
Table 11. Average Hourly Frequencies of Outdoor Temperature for

Occupied and Unoccupied Periods for Omaha, Nebraska

Outdoor Occupied Hours Unoccupied Hours ^ Temperature. *F Per Year Per Year Total

-16. 0. 0. 1. -14. 1. 1. 2. -12. 0. 2. 2. -10. 1. 5. 5. -9. 2. 7. 8. -6. 2. 10. 12. -4. 3. 14. 17. -2. 6. 18. 23.

0. 8. 22. 30.

2. 12. 28. 39.

4. 14. 35. 48.

6. 12. 39. 51.

8. 15. 49. 64.

10. 18. 52. 70. 12. 20. 58. 78.

14. 26. 74. 100.

16. 25. * 74. 100.

18. 32. 91. \ 123.

20. 39. 102. 141.

22. 46. 113. 159.

24. 49. 131. 180.

26. 50. 145. 195.

28. 55. 170. 225.

30. 58. 189. 247.

32. 64. 208. 272.

34. 73. 214. 287.

36. 68. 182. 249.

38. 66. 175. 241.

40. 61. 173. 234.

42. 65. 152. 217.

44. 62. 157. 219.

46. 56. 147. 202.

48. 56. 141. 197.

50. 63. 146. 209.

52. 60. 149. 209.

54. 59. 168. 228.

56. 58. 164. 222.

58. 52. 167. 220.

60. 64. 180. 244.

62. 65. 188. 253.

64. 69. 219. 288.

66. 76. 212. 288.

68. 80. 214. 294.

70. 89. 217. 306.

72. 87. 183. 271.

74. 5:

.

194. 286.

76. 78. 163. 242.

78. 75. 143. 218.

80. 78. 126. 204.

82. 66. 105. 170.

84. 65. 91. 156.

86. 54. 61. 114.

88. 43. 50. 93.

90. 35. 38. 73. 92. 27. 27. 55.

94. 18. 19. 38.

96. 9. 9. 17. 98. 7. 5. 12. 100. 4. 3. 7. 102. 2. 2. 4. 104. 1. 1. 2. 106. 0. 0. 1.

TOTAL 2542. 6225. 8767.*

The average total number of hours would vary from 8765 to 8767 depending

upon the number of leap years included In the calculation period.
Table 12. Average Hourly Frequencies of Outdoor Air Enthalpy for

Occupied and Unoccupied Periods for Omaha, Nebraska

Outdoor Air Occupied Hours Unoccupied Hours

Enthalpy, Btu/lb . Per Year Per Year - Total

T \j . X1 . 1

.. -J • _2 ' X19 • 1 s 4 ' 90 24

47

1 V XO • AS 63

2 2Q 81 110

.

28 8"^ 110.

98 132

XX\J • 161

6 60 X^ ^ • 212 ^ X ^ • 7 74 XO1 8SJ . 259

RA 1 so 204.

q ^978/ 0

.

374

J.KJ • 7n 99n 9Q17 X • XX117/ . "^AA AA9

x^ • xuu

.

9A7 JO / • X J « xuo

.

3Afi XH • vim 9 "^7

1 Q J. J • p.n X1 7 S / J . 9SA

xO1

• DO . 1 S^ 99 S X / • , 7 9 XD7 1 AQ . ^HX 9A1 •

1 ft 0 J

.

1 "^1 X3X

.

^XD 91 A .

1 Q

' Anou

.

X J J • ^XJ 91 S . AQ " 1 9 X<^ J

.

17"^ X / J • 9 1 Aft Do • ±Y 7Qly . 9A7

7Qly. 1 ftQ xoy

.

^DO 9 Aft . 9 J / . xzx. 191 X1 7ft / 0

.

9A ft 9 1 ftft

, Xoo . 970

9 > 11"^ XXj . xoo 1 Aft

.

9fi . • 7Q ' • • ^Xu . 98Q

97 A'^ xuy 1 nQ

.

Xj1 S9u • 98 7D . 99 A 9Q 1 S9 91XOA . 0 J * xjy . JX • 7ft 1 '^7 XJ / . 9

S

z J J • "^9 ftn OU . ZUo 9nft . ^9ftft 00

.

J J • AA lift -LXo . xoz. 1 A9

.

Jl • "^7 XX^t 1 1 A

.

X179/ ^ . JJ

.

/.I 0 J

.

1 9A

jO . / 0 4^ . onyu. 1 '^9

-3 / • T7 71/ X

.

xuo 1 nft • ^ft A70 / . xu1 r»7/ • jX . AlDX . Q9

40. 24. 38. 61.

41. 19. 29. ; 49 .

/. 0 h/ . . 43. 6. 9. 15.

44. 4. 4. 8.

45. X. 2. 3.

46. 0. 1. 1.

TOTAL 2542 6225 8767*

The average total number of hcurs would vary from 8765 to 8767 depenciing upon the

number of leap years Included in the calculation period.
Table 13. Average Hourly Frequencies of Outdoor Temperature for

Occupied and Unoccupied Periods for Orlando, Florida

Outdoor Occupied Hours Unoccupied Hours

Temperature, °F Per Year Per Year Total

26. 0. 0. 1.

28. 0. 1. 1.

30. 0. 2. 2.

32. 1. 4. 5.

34. 1. 7. 8.

36. 4. 15. 19.

38. 4. 21. 25.

40. 6. 34. 40.

42. 7. 44. 51.

44. 10. 57. 67.

46. 14. 74. 88.

48. 15. 84. 99.

50. 18. 104. 122.

52. 23. 122. 145.

54. 30. 139. 169.

56. 39. 168. 207.

58. 48. 213. 262.

60. 53. 239. 292.

62. 65. 283. 348.

64. 82. 333. 415.

66. 91. 372. 463.

68. 92. 382. 474.

70. 126. 430. 555.

72. 136. 586. 723.

74. 178. 713. 891.

/O . Do J . 7 A Q

78. 201. 347. 548.

80. 208. 246. 454.

82. 201. 186. 387.

84. 188. 143. 331.

86. 163. 117. 280.

88. 147. 92. 239.

90. 107. 57. 165.

92. 56. 33. 89.

94. 22. 10. 33.

96. 4. 1. 5.

98. 1. 0. 1.

TOTAL 2542 6225 8767**

* Due to rounding-off arithmetics, the total hours may not exactly match the sum

of occupied and unoccupied hours.

** The average total number of hours would vary from 8765 to 8767 depending upon

number of leap years included in the calculation period.
Table 14. Average Hourly Frequencies of Outdoor Air Enthalpy for

Opcupled and Unoccupied Periods for Orlando, Florida

Outdoor Air Occupied Hours Unoccupied Hours

Enthalpy, Btu/Xb Per Year Per Year Tota

8. 0. 1. 1.

9. 0. 3. 3.

10. 1. 4. 5.

11. 3, 8. 11.

12. 8. 23. 31.

13. 7. 26. 33.

14. 11. ^ 42. 53.

15. 14. 55. 69.

16. 20. 71. 91.

17. 27. 93. 120.

18. 29. 101. 130.

19. 32. 120. 151.

20. 43. 143. 186.

21. 47. 159. 206.

22. 29. 94. 123.

23. 71. 219. 290.

24. 61. 166. 227.

25. 59. 221. 280.

26. 89. 214. 303.

27. 87. 281. 368.

28. 72. 205. 276.

29. 166. 402

.

569.

30. 102. 258. 361.

31. 97. 236. 333.

32. 116. 265. 381.

33. 200. 381. 581.

34. 121. 380. 501.

35. 117. 385. 503.

36. 120. 406. 525.

37. 137. 416. 553.

38. 200. 417. 617.

39. 175. 221. 396.

40, 168. l< 141. 309.

41. 83. 55. 138.

42. 20. 11. 31.

43. 7. 2. 9.

44. 1. 0. 1.

TOTAL 2542 6225 8767

The average total number of hours would vary from 8765 to 8767 depending upon

the number of leap years Included in the calculation period.
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U.S. DEPT. OF COMM. 1, PUBLICATION OR RKPORT NO. 2. Gov't Accession

BIBLIOGRAPHIC DATA

NBSIR 76-1088

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Estimating the Energy Conservation Potential of

Ventilation Control Through Weather Data Analysis

5. Publication Date August 1977

6. Performing Organization Code

7. AUTHOR(S)

T. Kusuda and J. W. Bean

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

nATIONAL dUkcAU Or STANDARDS

DEPARTMENT OF COMMERCE -^-.-.U WASHINGTON, D.C. 20234 „- - ^

10. Project/Task/Work Unit No. 4626403

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Federal Energy Administration

New Post Office Building

12th and Pennsylvania Avenue

Washington, D.C. 20461

13. Type of Report & Period Covered

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual sumtrtary ol most signilicartt inforwalion. If document includes a significant

bibliography or literature survey, mention it here.) Hourly weather data for six selected cities in the United States covering eleven

consecutive vears were analyzed to aid in estimatina the oossible pnerav "^avina that

could be achieved by closing the outdoor dampers during unoccupied hours. The

analysis shows that, depending upon the local weather condition, and with some simplifying assumptions, from 74 to 83 percent of the energy used for heating the

make-up air could potentially be saved by closing the outdoor dampers when the

building is not occupied. Based upon a premise that the energy required for

cooling the outdoor ventilation air is proportional to the average enthalpy

difference between the outdoor air and the air leaving the cooling coil, from

53 to 63 percent of the energy for cooling of ventilation air could be saved by

closing the outdoor dampers during unoccupied hours.

Hourly temperature and enthalpy values are presented in histogram form for occuoied

and unoccupied periods (office use), with the suggestion that similar data processing

be carried out for other cities as well.

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) Air Conditioning requirements; energy conservation;

intermittent ventilation; ventilation control; weather data analysis

18. AVAILABILITY [X' Unlimited

1

' For Official Distribution. Do Not Release to NTIS

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

IX 1 Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151

19. SECURITY CLASS

(THIS REPORT)

UNCL ASSIFIED

21. NO. OF PAGES

50

20. SECURITY CLASS

(THIS PAGE)

UNCLASSIFIED

22. Price

$4.00

USCOMM-DC 29042-P74