Document 91NqjOdZge3ZLY8eZjOkqMdR

170 CHAPTER 9 1955 Guides Table 1. Conductances (C) fob Surfaces and Aib Spaces All conductance values expressed in Blu per (hr) (sq ft) (F deg temp diff) Section A. Surface Conductances for Still Air Position of Surface Direction of Heat Flow Surface Emissivity e =U90 e = 0.05 Upward Horizontal 1.95 1.21 1.52b 1.16 0.44 0.74 '^-}k ' '1 -T. a Radiation and Convection from Surfaces in Various Positions, by G. B. Wilkes and C- M. F. Peterson}?^ (A.S.H.V.E. Transactions, Vol. 44, 1938, p. 513.) Conductances are for surfaces of the stated eznissivityip facing surroundings having an emissivity equal to 0.9 and at the same temperature as the ambient air. ,[s: b The recommended surface conductance for calculating heat losses for still air for non-reflective surfaces^-' is 1.65 Btu. For a 15 mph wind velocity, the recommended value is 6.0 Btu. These coefficients were de-'jtT rived from Fig. 4, based on tests conducted at the University of Minnesota, and apply to vertical surfaces.^ ** Position of Air Space Section B. Thermal Conductances and Resistances of a Plane*Air Space* Heat Flow ThickNESSb Inches Mean Temp F Temp Diff deg Conductance-C Value of E'd Thermal Resistance-j Value of Ea rtZ r 0.05 0.2 0.5 0.82 0.05 0.2 0.5 0.82 Horiz. 45* Slope Vert. 45* Slope Horiz. Up Up Horiz. Down Down* X to 4 54 to 4 54 to 4 54 to 4 54 4 54 ltf 4 50 50 90 50 50 90 50 50 90 50 50 90 50 50 50 90 90 90 I10 0.41 0.55 0.82 1.11 2.44 1.83 1.22 0.90 30 0.54 0.68 0.95 1.24 1.84 1.47 1.05 0.80 sc 10 0.41 0.58 0.92 1.28 2.47 1.73 1.09 0.78 K 10 0.35 0.49 0.76 1.05 2.84 2.05 1.31 0.95-vjr. 30 0.48 0.62 0.89 1.18 2.08 1.62 1.13 0.85 V 10 0.35 0.52 0.86 1.23 2.85 1.92 1.16 o.8i * 10 0.28 0.42 0.69 0.99 3.52 2.37 1.44 1.02 * 30 0.38 0.52 0.79 1.08 2.64 1.94 1.27 0.92 V 10 0.29 C.46 0.80 1.16 3.49 2.19 1.25 0.88 ft 10 0.24 0.38 0.65 0.94 4.14 2.65 1.54 I.OS*. 30 0.30 0.43 0.71 1.00 3.36 2.30 1.41 1.005? 10 0.25 0.42 0.76 1.12 4.07 2.40 1.32 0.89 20 0.28 0.42 0.69 0-98 3.57 2.38 1.45 1.02c 20 0.18 0.31 0.58 0.87 5.56 3.23 1.73 1.15*-: 20 0.11 0.25 0.52 0.81 8.94 4.03 1.92 1.23.- 20 20 0.31 0.20 0.48 0.37 0.82 0.71 1.18 1.07 3.23 5.00 2.08 2,70 1.22 1.4i "0.9S3t- 20 0.13 0.30 0.64 1.01 7.82 3.35 1.56 0.99' Notes: a Spaces of uniform thickness, bounded by moderately smooth surfaces. ' b Where a range of thickness is given, the given conductance is the average over the range; extreme . values within the range differ therefrom by less than 10 percent. ! c Interpolation, and moderate extrapolation, of conductance values is permissible for other v&Iuefl of. mean temperature, temperature difference and effective emissivity B. d Effective emissivity of space, B, is given by ~ -- 1 where ei and ej are the emissiviti` of the surfaces of the air space, (See Section C. Table 1). '.y, * The conductances of horizontal spaces with heat flow downward are substantially independent of * temperature difference. * Based on National Bureau of Standards data presented in Housing Research Paper No. 32, Housing aid Home Finance Agency, 1954 (U. S. Government Printing Office, Washington, D. C.) Section C. Reflectivity and Emissivity Values of Various Surfaces and Effective Emissivities of Air Spams Surface Reflectivity IN PERCENT Building materials; wood, paper, glass, 92 to 97 80 to 95 75 to 84 70 to 80 30 to 70 5 to 15 Average Emissivity e 0.05 0.12 0.20 0.25 0.50 0.90 Effective Emissivity S:> of Air space , With one sur With both .' face having emissivity e and other 0.90 surfaces or emissivity 0.05 0.12 0.20 0.24 0.47 0.82 0.03 0.06 0.11 0.15 0.35 ' 0.82 _-- Heat Transmission Coefficients of Building Materials 171 Table 2. Conductivities (A) and Conductances (C) of Building and ' - Insulating Materials (design values)* These constants are expressed in Btu per (&our) (square foot) (Fahrenheit degree temperature difference). Conductivities (k) ore per inch thickness and conductances (C) are for thickness or construction stated, not per inch thickness. Material BUILDING BOARDb SIDING MATERIALS (On Flat Surface Including Building Paper)6 masonry materials .Concretes Co.vDucnvrr Y OR Resistance Conductanc e Description (Lb. pej* Cu Ft; (k) Plywood Laminated or homogeneous wood fiber board.. / l Wood fiber--hardboard type........................... Gypsum or plaster board............................ Hi n. Gypsum or plaster board............................ Hi Asbestos-cement board....................................... n. Shingles Wood, 16-in. 7H-in. exposure................ Wood, double, 15-in., 12-in. exposure.. Asbestos-cement........... ............... Siding Drop, 1 x 8 in.. ........ ......... ......... BeveL Vt * 8 in., lapped........................ Bevel, x 10 in., lapped...................... Plywood, H in-, lapped......................... Asbestos-cement, H in., lapped........... Sand and gravel or stone aggregate.. Cement mortar and stucco................ 34 0.80 26 0.42 31 0.50 1.40 50 -- 50 -- 4.0 -- -- -- ---- -- i-- ---- 140 9.0 116 5.0 Per For IncJ Thick- (C) Thiel - ness ness Listed a:>G) _-- 1.25 2.38 __ -- 2.00 -- __ 0.72 3.10 2.25 __ 0.32 0.45 -- 0.25 1.10 0.80 2.85 1.18 1.15 0.90 1.54 3.70 _ -- -- -- __ -- -- --. -- 0.11 0.20 0.93 1.25 0.35 0.85 0.87 1.11 0.65 0.27 -- masonry UNITS concretes wood chips.. d 120 ; 100 r 80 60 40 30 20 0 51 Common brick.............................. Face brick........... Three-oval core concrete blocks: Sand <k gravel aggregate........................... 4 in Send & gravel aggregate........................... 8 in Sand & gravel aggregate....... ................ 12 in 120 130 .-- -- -- Cinder aggregate....... 4 in. -- - Cinder aggregate................................. 8 in. Cinder aggregate............................................... 12in. -- [ Lightweight aggregate (expanded f 4 in. . ' shale, clay, slate or slag; pumice)......... i Sin. \12 in. -- -- -- 1 Hollow clay tile.............................................. 3 in. I Hollow clay tile..............................-.............. 4 in. i Hollow clay tile................................................... 6in. i Hollow clay tile................................... 8 in. Hollow clay tile.....................................................10m. Hollow clay tile................................................ 12 in.I -- -- -- -- -- Gypsum partition tile: 3 x 12 x 30 in. solid.................................... 3 x 12 x 30 in. 4-cell................................... 4 x 12 x 30 in. 3-cell.................................. __ -- 5.2 3.6 2.5 1.7 1.15 0.90 0.70 1.66 5.0. 9.0 -- -- -- ~ -- -- -- -- --- -- -- -- ~ _ -- Gypsum plaster Sand aggregate............................ Vermiculate aggregate................ Perlite aggregate......................... Cement plaster, sand aggregate.. 105 5.6 45 .7 45 .5 116 5.0 __ -- -- -- _ __ -- _ -- 1.40 0.90 0.78 0.90 0.58 0.53 0.67 0.50 0.44 1.25 0.90 0.66 0.54 0.45 0.40 0.19 0.28 0.40 0.59 0.86 1.11 1.43 __ ___ 0.60 __ 0.20 0.11 -- __ -- 0.71 1.11 -* 1.28 __ l.U -- 1.72 -- 1.89 __ 1.50 -- 2.00 -- 2.27 _ __ 0.80 1.11 -- 1.52 -- 1.85 -- 2.22 -- 2.50 0.79 0.74 -- 0.60 1 -- 1.26 1.35 .67 _-- ( .18 -- i .59 -- i .67 -- C .20 --