Document OzdqEk1z9QejqJ6Rb3oVo2eL1

126 CHAPTER 6 :: 1946 Guide 7i = ;_______________________________ :_________________ ` _ 1 _ n 97 0.17 + 0.44.+1.16 + 0.91 + 0.42 + 0.61 .3.71 . When 2 in. of but.insulation is added in the air space in the wall, an air space will still be left since it was originally .3% in. widp. Then,.... ............... ' .............. U= 1 3.71 + 0.27 11.11 = 0.090 This coefficient (0.090) applies only to the wall where no studding or framing is present and is assumed to constitute 85 per cent of the whole wall. ' Then for 1 sq ft of wall the heat transfer through the insulated portion is 0.85 X 0.090 or 0.0765 Btu. ... In the portion of wall where framing is present, the air space will be replaced with an equivalent thickness of wood framing. Then, U (through framing) = 6.0 + 1 2.27 + 1 0.86 + 3.625 0.80 +o+ 1 1.65 U = 0.136 Then for 1 sq ft of wall the heat transfer through the framing is 15 per cent of 0.136 or 0.0204 Btu. The total beat transfer through 1 sq ft of wall (with 3% in. framing covering 15 per cent of area) equals U (corrected) = 0.0765 + 0.0204 = 0.097 Btu This is the value shown for No. 49-B in Table 6, which is included to eliminate the need :for the calculation of framing corrections when insulation, is used in frame con struction. In making the calculations for values of V shown in Tables 5 to 18, the following conditions have been assumed: Equilibrium or steady-state heat transfer, eliminating effects of heat capacity. Surrounding surfaces at ambient air temperatures. Exterior wind velocity of 15 mph. Surface emissivity of ordinary building materials = 0.83. No correction for position or direction of heat flow. (Average coefficients used). ' Air spaces are M in. or more in width. Variation of conductivity with mean temperature neglected. ' - Corrections for framing made on basis of parallel heat flow through 2X4 in. (nominal) , studs, 16 in. on centers, the framing covering 15 per cent of wall area. Actual thicknesses of lumber assumed to be as follows: ................. .. Nominal Actual 1 in. (S-2-S)__ _________ jl*.fc2 in. l'A in. (S-2-S)____________'_____________ iy16 in. 2 in. (S-2-S);__..____ ........................... .... .1% in. 2% in. (S-2-S)___________________ in. 3 in. (S-2-S)..................................... 1____2% in. 4 in. (S-2-S)........ ............ t:____________ 3Yi. in. Finish floorings .(maple or. oak)-TKe i"- : Coefficients for frame construction are corrected for the effect of framing where such correction would increase the coefficients, but not where the correction would decrease the coefficients 7. It should be noted that the effects of poor workmanship in construction and installation have an increasingly greater percentage effect on heat transmission as the coefficient becomes numerically smaller. ;. Failure to meet design estimates may be caused by lack of proper attention to Heat Transmission Coefficients of Building Materials 127 Table 7. Coefficients, of Transmission (7) of Masonry Walls Coefficients are expressed in Btu per (hour) (square foot) (Fahrenheit degree difference in temperature between the air on the two sides), and are based on an outside wind velocity of 16 mph. TYPE OF MASONRY 0 1 L |-l EE INTERIOR FINISH (Plus Insulation Whbbb Indicated) 3 3 I i i 2 ii 5 1 S* ?i Si t i! w i 1j 3 31 s* il 11 1 E al ag GO Sa opn 3-2 fc HH.2H^=t M 3 meA il .go.* 30t cDE FOH 1 051 0.31 055 0.21 0.30 0.24 0.20 052 0.10 0.17 022 0.10 0.16 0.16 0.U 0.13 0.14 0.13 042 67 69 8 0.56 12 . , 0.40 032 1 0.34 I 034 L 032 0.46 032 1 031 1 030 054 052 053 052 0.17 046 045 1 82 044 | 83 . 8 1 0.41 1.0.39 0.28 12 028 026 0.26 Cinder Aggregate 0.28 026 057 051 0.25 0.20 050 L 045. 043 .. 83 0.10 1 045. 043 85 ' Light Weight Aggregate- 8 12 0.36 0.34 0.34 | 0.26 1 0.25 0.33 1 055 1 054 054 1 0.10 1 0.10 1 0.15 U.W 0.24 1 0.19 1 0.18 1 0.14 | 0.13 87 "Based on 4 in. hard brick and remainder common brick. *Tbe 8 in. and 10 in. .tile figures are based on two ceils in the direction of heat Sow. The 12 in. tile is based on three cells in the direction of heat Sow. s ThelBin. tile consists of one 10 in. and one 0 In. tile each having two cells in the direction of heat flow. "Limestone or sandstone. : : *These figures may be used with sufficient accuracy for concrete walla with stucco exterior finish. Expanded slag, burned clay or pumice. 'Thickness of plaster assumed % in. oThfoirnpsa of'nlaster assumed V4 in. !,