Document g2YR66r16pzd3aLJJKZV1v9xa

186 CHAPTER 9 1951.Guide Table 5. Conductivities (k) and Conductances (C) Used in Calculating Heat Transmission Coefficients (U) in Tables 6 to 19 These Constanta arc expressed * Btu per (hour) (square foot) (Fahrenheit degree temperature difference). Conductivities (k) are per nek thickness and conductances (C) are for thickness or construction stated, not per inch thickness Conductivity or Conductance Resistance MaTEBUIi Description G) G)(*> m Per Inch Thick ness For Thick ness Listed AIR SPACES . Bounded bt Ordinary Ma- Bounded bt Aluminum Foil. Vertical9, $ in. or more in width........... -- 1.10 0.46 -- 0.91 2.17 EXTERIOR FINISHES (Frame Walzh) 12.50 Yellow Pine Lap Siding ... INSULATING MATERIALS Made from-mineral or vegetable fiber nr animal huir. Anriraftd nr nnftn. Mineral Wool............................. Fiber made from rock, slag or glass... -- 0.27 0.30 0.33 0.27 0.48 2.27 1.28 1.28 0.08 __ -- --- -- 3.70 3.33 __ 3.03. -- 3.70 . 2.08 0.44 0.78 0.78 -- -- -- __ INTERIOR FINISHES Composition Wallboabd. ... A in. to I in. thick....................................... 0.50 3.30 Gypsum Lath (| en.) and Insulating Board ($ in.) . .. Plain or decorated........................................ -- Insulating Board Lath Metal Lath and Plasteb. .. Plaster thickness assumed j in............... Wood Lath and Plasteb___ -- -- -- 3.70 2.4 0.66 0.60 0.31 4.40 2.12 2.50 2.00 0.30 -- ---- -- 0.27 0.42 ` 1.52- " 1.67 1 3.18 -- 0.23 0.47 -- . 0.40 MASONRY MATERIALS nnt p Brmr -- __ 12.00 Concrete......................................... Light weight aggregate^............................ ___ ___ ___ 2.50 12.00 4 in. Concrete Blocks......... Hollow, cinder aggregate........................... -- _ Hollow, cinder aggregate........................... 8 in. Concrete Blocks......... Hollow, light weight aggregate?....... -- -- Gypsum Fiber Concrete------- 87$ percent gypsum and 12$ percent wood chips..................................... -............ 1.66 - __ 12.50 12.00 12.50 0.89 1.25 2.30 1.28 1.00 0.64 0.60 0.58 0.40 0.31 1.28 1.00 1.00 0.80 0.60 0.53 0.50 0.47 --. -- -- 0.08 -__ __ , __ __ __ __ 0.40. 0.08 __ --, __ __ -- -- .-- 0.61 0.46 __ 0.60 _ 0.08 0.08 0.08 1.12 0.80 0.43 __ 0.78 .1.00, -1.67 1.67 1.72 2.50 3.23 0.78 .. 1.00 1.00 1.25 1.66 1.88 2.00 . -- 1.64 2.18 --_ Conductance values for horizontal air spaces depend on whether the heat flow is upward or downward, but in mat cases it is sufficiently accurate to use the same values for horizontal as for vertical air spaces. * Expanded slag, burned clay or pumice. ' 1 Heat Transmission Coefficients of Building Materials ; 187 Table 5. Conductivities (&) and Conductances. (C) Used in Calculating Heat Transmission Coefficients (U) in Tables 6 to 19--Concluded These constants are expressed in Btu per (hour) (square foot) (Fahrenheit degree temperature difference). Conductivities (k) are per inch thickness and conductances (C) are for thickness or construction stated, not per inch thickness. Conductivity OB Conductance Resistance Material Description G) G)< (CT Per Inch Thick ness For . *rhiok/ ness Listed ROOFING MATERIALS ASBESTOS Shingles....................... Built-up Roofing......................... Assumed f in......................... 10.00 6.00 6.50 3.53 6.50 20.00 1.28 SHEATHING Insulating Board (f$ in.). .. Fib ob Yellow Pine (1 in.). Fib. Plus Building Paper .. 2.82 0.42 2.66 -- 1.02 0.86 SURFACES Ordinary non-reflective materials, Ordinary ' non-reflective materials, vertical................................................. - 1.65 6.00 WOODS Fib Sheathing (1 in.) Build ing Paper and Yellow 1.15 0.80 0.50 0.10 -- - 0.87 1.25 0.17 0.15 0.28 0.15 0.05 0.78 0.35 2.37 0.39 0.98 1.16 0.61 0.17 2.00 ities. Since there is some variation in the resulting values due to varia tions in materials and in test conditions, average values for the usual con ditions encountered in building practice have been selected and listed in Table 5. These coefficients were used in the calculation of overall coeffi cients given in Tables 6 to 19. These tables constitute typical examples of combinations frequently used, but any special constructions not given can be computed by the .use of the conductivity or conductance values in Table 2 and the fundamental heat transfer formulas. Caution The user should realize that the average conductivity and conductance values given in Tables 2 or 5 do.not necessarily apply to all products of the same general description. In using these values, judgment should be exer cised with regard to the extent to which the product (either as received or as applied) will comply with the tabulated values. Exact conductivities or conductances for specific materials should be obtained from the maker. Insulating Materials In order to determine the benefit derived from the addition of insulating materials to a given construction, the overall coefficient of heat transmis sion U\ of the insulated construction may be compared with the corre sponding coefficient U without insulation. Attention is called to the' necessity of applying the insulating material in accordance with the manu facturer's specification. The engineer must evaluate carefully the eco-