Document BN1Qrk520km4rBDVaNMd27YX

American Society of Heating and Ventilating Engineers Guide, 1924-25 When windows and other openings are not weather-stripped an allow ance of 10 to 15 per cent for exposure due to prevailing winds should be added to the computed heat losses. As the room mentioned faces the north, and is not weather stripped ' add 15 per cent of computed heat losses. 6520 X 1.15 = 7498, total heat loss If the ceiling construction in the room was lath and plaster with floor above and the space above was not heated the room should be figured as follows: Referring to Table 7 it is found that the heat loss per degree, per square fqot to be 0.26 B.t.u. per hr. Special note should be taken that this space will be only 35 deg. fahr. when it is zero outside, and as the room is heated to 70 deg. fahr. the temperature difference will be 70 -- 35 = 35 deg. Cubical contents 800 X 134 X 0.02 X 70 = 1480 B.t.u. Glass 30 X 1.1 X 70 = 2310B.t.u. Net wall 130 X 0.3 X 70 = 2730B.t.u. Ceiling 100 X 0.26 X 35 = 910B.t.u. Total Heat Loss from' Room = 7430 B.t.u. Adding 15 per cent for Northern Exposure = 8544 B.t.u. EFFECT OF EXPOSURE AND WIND VELOCITY As shown in the section on calculation of heat loss, it is customary to add 10 per cent to 15 per cent to the heat loss of rooms on the sides of the building exposed to the prevailing winds in coldest weather. The coldest exposure varies with the location. North and west are usually considered the coldest exposure. According to the U. S. Weather Bureau (Table 14), the coldest exposure in Salt Lake City is S.E.; in Denver, S.; in Chicago, S.W.; in Albany, S., which indicates how important it is to know not only the average and lowest temperatures of a place but also the prevailing wind directions in winter. Every plan should show the "points of the compass." TABLE 13. DROP IN TEMPERATURE FOR EACH MILE WIND VELOCITY Temp. Deg. Fahr. 50 deg. to 40 deg. 40 deg. to 30 deg. 30 deg. to 20 deg. 20 deg. to 10 deg. 10 deg. to 0 deg. 0 deg. to --10 deg. -- 10 deg. to --20 deg. Wind Velocity 1 mile per hr. equals 1 mile per hr. equals 1 mile per hr. equals 1 mile per hr. equals 1 mile per hr. equals 1 mile per hr. equals 1 mile per hr. equals Deg. of Temp. Drop 0.75 deg. drop 1.0 deg. drop 1.1 deg. drop 1.2 deg. drop 1.3 deg. drop 1.4 deg. drop 1.5 deg. drop In other words a temperature of 5 deg. above zero with a 30-mile wind should be equivalent to 34 deg. below zero with no wind blowing. It will be found, however, that the coefficients for transmission allow for a wind velocity of from 10 to 15-miles per hr. 18 American Society of Heating and Ventilating Engineers Guide, 1924-25 TABLE 14. CLIMATIC CONDITIONS COMPILED FROM U. S. WEATHER BUREAU RECORDS Col. A State Ala A ri Arlr Pal Prtln Prtnp nr FU Pa TrloVwo 111 IriTira Kans................. i Md. Col. B City Mo NH NJ NV N. M. Col. C Col. D Col. E Col. F Average Temp., Oct. 1stMay 1st Lowest Tempera ture Average .Wind Vel ocity Dec., Jan., Feb.. Miles per Hr. Direction of Prevail ing Wind, Dec., Jan., Feb. 57.7 53.9 59.5 34.9 49.5 51.6 54.3. 58.6 39.3 39.2 38.0 43.2 61.9 51.4 58.4 42.5 36.4 36.4 39.9 40.2 44.1 33.9 32.1 38.9 40.2 45.2 61.5 56.2 .31.1 33.6 43.6 37.6 29.1 35.4 27.6 25.1 29.6 56.0 40.3 43.3 43.0 34.7 27.7 37.0 34.6 39.6 37.9 33.4 41.6 35.1 34.7 40.3 38.0 -i -10 16 -25 -15 -12 29 28 -29 -16 -14 -15 10 -8 8 -13 -20 -23 -24 -25 -15 -32 -35 -25 -26- -20 7 -5 -23 -17 -7 -13 -27 -24 -27 -41 -33 -1 -24 -22 -29 -49 -57 -29 -35 -7 -28 -35 -7 -24 -14 -6 -13 8.3 8.6 3.9 6.7 8.0 9.9 7.4 5.6 9.3 7.3 8.2 11.8 8.3 4.7 9.3 17.0 10.2 11.8 8.4 6.1 12.2 7.3 10.4 9.3 9.6 7.7 13.8 10.1 7.2 11.7 11.3 13.1 11.4 11.1 11.5 . 7.6 9.1 11.8 11.3 . 8.7 10.9 9.0 9.9 9.5 6.0 10.6 7.9 17.7 13.3 7.3 NN E SW E NW N. NE S SE N NW NE NW NW E SE SW NW S S NW NW N NW SW N SE W NW NW W W SW NW SW NW SE NW NW SE W SW N W SE NE NW NW S w NW NE 19