Document OgGxwgdmN7RV2bELKgn8yKMe

AMERICAN SOCIETYOF HEATING & HHS) YENT1LAT1W6ENGINEERSGDH)EJ9g3^ If it is desired to figure on a basis of the number of air changes the expression would be N Wp X Jh in which N = Number of air changes Wp = Window crack perimeter /h = Infiltration per hour per lineal foot of cracks C = Cubical contents The crack perimeter of a double hung window is four times the height, and three times the width of the lower sash. The perimeter of doors is the width plus the height times two, single casements the same, double casements twice the width and three times the height. COMPARISON OF FUEL QUANTITIES AND COSTS TO HEAT AIR ENTERING VARIOUS SLIDING SASH WINDOWS, AS AIR INFILTRATION OR INLEAKAGE. ASSUMING 85 PER CENT OVER ALL EFFICIENCY OF HEATING PLANT Window, 3x7 ft. Crack, 23 lin. ft. Wind, 20 miles per hr. B.t.u. to raise 1 cu. ft. air from zero to 70 deg., 1,439 B.t.u. per lb. best coal, 13,080 Duration heating season, 130 days Cost coal, $6.00 per ton Overall efficiency of heating plant, 65 per cent (high) Net B.t.u. = 13,080 X 0.65 = 8500 B.t.u. effective leakage. A. Unstripped window, 114 cu. ft. per hr. per ft. crack B. Plain Rib Strip (3 miles), 55.8 cu. ft. per hr. per ft. crack C. Metal Weather Strip, 24 cu. ft. per hr. per ft. crack A. 23 X 114 X 1.439 8500 = 0.445 lb. coal per hr. 0.445 X 24 2000 X 130 = 1385 2qqq = 0.694 tons per season $6.00 X .694 = $4.16 per season B. 23 X 55.8 X 1.439 8500 = 0.218 lb. coal per hr. 0.218 X 24 X 130 680 = 0.34 tons per season 2000 " 2000 $6.00 X .34 = $2.04 per season 23 X 24 X 1.439 8500 = 0.0935 lb. coal per hr. 0.0935 X 24 X 130 292 = 0.146 tons per season 2000 - 2000 $6.00 X 0.146 = $.875 per season 112 Fuel cost per window-- Without weather strips...... .......................... With Rib strip................................................ With metal adjustable................................. $4.16 2.04 .875 Fuel saved with-- Rib strip.......................................................... Metal adjustable.................................... ;...... Metal vs. Rib................................................. $2.12 3.285 1.165 The above is based on infiltration on windward side of building. Room, 15X15X10 = 2250 cu. ft. Wall, 300 net = 264 sq. ft. Crack Aperture, 42 ft. Glass, 36 = 36 sq. ft. Ceiling, = 225 sq. ft. Two windows, 3x6, crack aperture, 2 x 21 ft. x H in. Wind velocity, ' 20 miles per hr. . Infiltration per Hour per Foof of Crack Wall...... .................................................... No. Strip 114 Cu. Ft. 5540 B.t.u. 2520 " 6900 " 4725 " 19,685 B.t.u. Rib Strip 55.8 Cu. Ft. 5540 Bit.u. 2520 " 3375 " 4725 " 16,160 B.t.u. Metal Strip 24 Cu. Ft. 5540 B.t.u. 2520 " 1450 " 4725 " 14,235 B.t.u. With equal consumption and radiation, inside temperature would be as follows: 4 19,685 B.t.u. 240 rad. eff. 60 deg. inside 59 sq. ft. rad. 38 in., 2 col., 0 deg. outside 16,160 B.t.u. 240 rad. eff. 59 sq. ft. rad. 38 in., 2 col., 65 deg. inside 0 deg. outside 14,235 B.t.u. 240 rad. eff. 70 deg. inside 59 sq. ft. rad. 38 in., 2 col.. 0 deg. outside 113