Document JJwR9d0x8p0NbwLjo482n5Kgr

American Society of Heating and Ventilating Engineers Guide, 1932 vertical wall spaces or ventilators may be estimated by means of the following formula: where t Utce -f- n to Ur Uce + n UT (11) t = inside temperature near ceiling. tb = temperature in attic, to = outside temperature. If in the foregoing problem, involving the determination of the com bined coefficient of transmission, the inside temperature t is 70 F and the outside temperature is -- 10 F, the attic temperature based on equation 11 will be: _ 70 X 0.588 + 1.2 X (-10) X 0.605 b 0.588 + 1.2 X 0.605 As previously stated, if the attic contains windows, ventilators, etc., the attic temperature will approach or equal the outside temperature, the roof will provide little or no resistance to the passage of heat, and the heat loss through the upper part of the building may be estimated by assuming the attic temperature to be the same as the outside tempera ture and using the heat transmission coefficient of the ceiling. The heat loss through floors into basements and into unheated rooms kept closed may be computed by assuming a temperature for these rooms of 32 F. AREAS WHERE TRANSMISSION LOSSES OCCUR Heat is lost from a building by transmission through all of those sur faces which separate heated spaces from the outside air or from unheated colder spaces within the building. In general, five kinds of surfaces are involved: (1) outside walls; (2) outside glass; (3) inside walls or parti 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 40 r Chapter 3--Heat Transfer Through Materials and Constructions Table 9. Coefficients of Transmission (U) of Solid Brick Walls*> Note.--These coefficients are expressed in Btu 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. The values of U in this-Table are based on the following Internal Conductivities or Conductances which are expressed in B.t.u. per Hr. perSq.Ft. per |"F Brick 5.00 per 1" Cement Mortar B.OO par 1" Plasterboard 3.75 per\ Raster (Gypsum) 2.5Z perl* Wood Lath 4 Plaster 2.00 as applied Cork board 0.50 per f Riqid insulation (Board form) 0.35 parl" Cellular Gypsum (18**) 0 51 perl" Flaked Gypsum, Dry (24**) 0.48 per 1" Split Furrinq Tile ly" 1 40 2*- 1.25 d( Y Thickness of insulation where specified V0). Interior Si 1 Construction 1 Plain Walls - hlo Interior Finish Thickness of Brick -X Y 8" \r Kb" AB C 0.385 0.285 0.238 2 Plotter on Brick. 3 J Plaster on Metal Lath - Furred 4 i PI aster on Wood Lath - Furred 0.356 0.26.1 0.250 0.277 O.ZIfe. 0.208 0.227 0.184 0.178 5 -j Planter oh A Plasterboard-Furred 5 Raster on Wood Lath on Z`Fumnq 6 Strips-Cellular Gypsum Fill c 7 z Plaster on Wood Lath on 2T Furrinq Strips -- Flaked Gypsum Fill 8 jr Raster on Qiqid. Insulation (Board form) Furred 8 10 -jr Plaster on Cork board set in 4^" _ Cement (V\orfcar II 12 h. Plaster on 1 * Split Furrinq Tile set aqainst Wall 13 % Plaster on 2" Split Furrinq Tile set aqainst Wall 0.251 a if 0.171 a if 0.154 1 0.181 1* 0.148 if 0.127 ZH 0-105 k___ 0.284 0.277 0.208 0.178 0.151 0.135 0.137 0.124 0.16.4 0.146, 0.132 0.120 0.115 0704 0.087 ' 0.080 0.231 0.185 0.227 0.182 Based on 1% in., the actual of 2 in. furring strips. bThe coefficients on thia page can also be used with sufficient accuracy for the Ideal Rolok-Bak Wall. The coefficient used for cellular gypsum, 0.59 is for 18 lb. weight-weights as low as 12 lb. may be used. 41