Document ZnZJKKB37Q08GonzbG4D5e1mJ

American Society of Heating and Ventilating Engineers Guide, 1928 tions next to unheated spaces, (4) ceilings of upper floors, either below a cold attic space or as the underside of a roof slab, and (5) floors of heated rooms above an unheated space. In most cases, only items (1) and (2), outside wall and glass surface, are considered. Failure to take account of the other heat losing surfaces, items (3), (4) and (5), when they exist in a building, has generally resulted in more or less dissatisfaction with the operation of the heating plant, as a result of failure to heat the rooms having such surfaces as indicated by items (3), (4) and (5). The net outside wall surface is usually determined by reference to the scale plans and elevations of the building concerned. In some cases of course, the actual building may have to be measured. The total area of all outside openings which are occupied by windows and doors is accurately measured and listed as glass. The glass area is then deducted from the total outside wall area for each room and the difference is the net wall area. The outside wall areas for any floor should be based on the vertical floor to floor heights and the horizontal distance from center to center of partitions separating different rooms. If there are no partitions, measure from inside face of one wall to inside face of next wall. The areas of walls, ceilings and floors next to cold or unheated spaces are found, of course, by taking the inside dimensions of such areas, measured on the heated side. CALCULATIONS FOR HEAT TRANSMISSION LOSSES The calculations for heat transmission losses are made by multiplying the area S. in square feet of wall, glass, roof or floor through which the loss takes place, by the proper coefficient {/ for such construction (Tables 6 to 12, or by computation as described underTransmission Coefficients by Computation) and by the temperature difference between the inside air temperature / at the proper level(in many cases not the " breathing line") and the outside air temperature to. Therefore, where Ht = SU (f-f,,) (9). Ht = B.t.u. per hr. transmitted through the material of the wall, glass, roof or floor, 5 = area in sq. ft. of wall, glass, roof or floor, taken from building plans or actually measured. (Use the net inside or heated surface dimensions in all cases.) . U = coefficient of heat transmission or B.t.u. per hr. per sq. ft. per 1 deg. fahr. difference between the inside and outside air temperature for air conditions such as exist in the given locality in coldest weather. (t -- to) = temperature difference between inside and outside air, in which t must always be taken at the proper level. Note that t may not be the " breathing, line" temperature in many cases. For examples showing application of equation (9) to practical examples; see Applications at the end of this chapter, in which the heat require- , meats are computed for typical cases. , 20 Chapter I-*--Calculating the Heat Losses prom Buildings Table 6-A. Coefficients of Transmission (U) of Various Types of Masonry Wall Construction ....__These coefficients are expressed in B.t.u. per hour per square foot per 1 deg. fahr. difference in temperature between the air on the two sides and are based on an outside wind exposure of 15 miles per hour. Solid Beicic Walls t The values <f U in this Table are based on the ./bllowmq Internal Conductivities (C) which are etpressed. in 6.t;u. per Ur. per sq.ft, per l f Brict Cement Mortar Plaster Board Plaster (Gypsum) Wood Lath 4 Plaster 5.00 per l. 8.00. per l_ 5.04 per I Z.3Z per f 2.00 as applied Cort board 0.30 per f fiber Insulation (Boon!/arm) >0.33 per l. Cellular Gypsum (16**) ' 0.54 per l Powdered Gypsum (26*) 0.52 per f Y -Thickness cf Insulation where spec:/led L V Si I 35 \ ntertor Construction i Pta*n Walls - Wo Interior Finish 2 ^Plaster on bride XThickness of brick - Y a 3` 18' 24* bcd - 0.358 0.278 0.218 0.173. \ 0. 332 0. 263 0.208 0.166 3 Sl Plaster on Uetat Lath - Furred 4 4 ^ Plaster on Wood Lath - Furred . 0.216 0.185 0.156 0.131 o.zoq 0.174 0.152 0.128 5 d* plaster on Planter board - Furred 0.215 0.184 0.155 0.131 j Plaster on Wood Lath on 2" Furnnq e Strips -- Cellular Qypsum Fill T. Plaster on Wood Lath on 7* Furrmq 7 Strips - Powdered Gypsum Fill 8 2 Plaster on Fibre Insulation -- C&oard/orm) Furred s 10 \ Plaster on Cork board Cement Mortar II Set m 'A 1% 0. 165 * tS/Q 0.156 0.lfeb 1' 0.133 .life' 0.1242" 0.103 0.146 0.128 0.138 0.122 0.147 0.128 0.120 0. 113 0.107 0.102 0.085 0.087 O.U( 0.106 o.m 0.085 0.080 O.07S Based on \% in., the actual thickness of 2 in. furring strips. tThe coefficients on this page can also be used with sufficient accuracy for the Ideal`Rolok-Bak Wall. 21