Document vVKpL22Qqb8mV30E23bXBrk4Z

HEATINC VENTILATING AIR CONDITIONING GUIDE 1944 Table 16. Combined Coefficients of Transmission (U) of Pitched Roofs3 and Horizontal Ceilings--Based on Ceiling Area6 Coefficients are expressed in Bin Per hour per square foot of ceiling area per degree Fahrenheit difference in temperature between the air on the two sides, and. are based on a wind velocity of 16 mpk. TYPE OF ROOFING AND ROOF SHEATHING CEILING COEFFI- CIENT/ Wooo'SHmaLEs ok Wood Strips* Asphalt Shingles6 on Roll Rooting ok Wood Sheathing* No Roof Insulation . (Rafters Exposed) (Ur = 0.48) H In. Ibsu- Latin* Board on Under Side of Rafters (Ur - 0.22) 1 In. Insulatin* Board on Under Side of Rafters (Ur = 0.16) No Roof Insulation (Rafters Exposed) Wr = 0.53) J4 In. Insu- latinK Board on-Under Side of Raftera (Ur = 023) 1 In. Insulating Board on Under Side of Rafters (Or = 0.17) a z A B 'C D E F 0.10 0.085 0.073 0.066 0.087 0.074 0.067 19 0.11 0.093 0.078 0.07 0.094 0.079 ' 0.071 20 0.12 0.099 0.082 0.074 0.10 0.083 0.075 21 0.13 0.10 0.087 0377 o.n 0.088 0.079 22 0.14 0.11 0.092 0.080 0.11 0.093 0.083 23 0.15 0.16 0.17 . 0.18 0.19 0.20 0.21 0.22 0.23 H 0.24 0.25 0.26 0.27 0.28 0-29 0.12 . 0.12 0.13 0.13 0.14 0.096 . 0.10 0.10 0.11 0.11 0.15 0.15 0.16 0.17 0.17 0.11 0.12 0.12 0.12 0.13 0.17 0.13 0.18 0.13 0.18 0.13 0.19 0.14 0.19 0.14 0.084 0.087. 0.090 0.093 0.096 0.098 0.10 0.10 0.10 0.11 0.11 0.11 0.11 0.11 0.12 0.12 0.13 0.13 0.14 0.15 . 0.15 0.16 0.17 0.17 0.18 0:18 0.19 . 0.19 0.19 020 ' 0.097 0.10 0.10 0.11 0.11 0.12 0.12 0.12 0.12 0.12 0.13 0.13 0.13 0.14 .0.14 0.086 0.089 0.092 0.095 0.098 24 26 26 27 28 0.10 0.10 0.11 0.11 0.11 29 30 31 32 33 0.11 0.11 0.12 .0.12 0.12 34 35 36 37 38 0.30 020 0.14 0.12 020 0.14 0.12 39 034 021 0.15 0.12 0.22 0.15 0.13 40 035 021 0.15 0.12 0.22 0.15 0.13 41 036 022 0.15 0.12 023 0.15 0:13 42 037 022 0.15 0.13 0.23 0.16 . 0.13 43 0.45 039 0.61 0.62 .0.67 0.69 025 029 029 '030 031 031 0.17 0.18 0.18 0.18 0.19 . 0.19 0.13 0J4 0.14 0.15 0.15 0.15 026 0.17 030 0.19 031 0.19 031 . 0.19 033 020 033 020 9.14 44 0.15 45 0.15 46 . 0.15 47 0.16 48 0.16 49 Calculations based on H pitch roof ( = 1.2) using the following formula: Ut y. Uot U = JJ11 Ur H-------- n U = combined coefficient'to be used with ceiling area. Ur = confident of transmission of the roof. Uca = coefficient of transmission of the ceiling. n = the ratio of the area of the roof to the area of the ceiling. *Use ceiling area (not roof area) with these coefficients. Coefficients in Columns D,' E and F may be used with sufficient accuracy for tile, slate and rigid asbestos shingles on wood sheathing. 4Based on 1 x 4 in. strips spaced'2 in. apart. Sheathing assumed In. thick. ____ , /Values of Uca to be used in column may be selected from Table 10. CHAPTER 4. HEAT TRANSMISSION COEFFICIENTS Table 17. Coefficients of Transmission (Z7) of Doors, Windows, Skylights and Glass Block Walls Coefficients are based on a wind velocity of 16 mph, and are expressed in Btuper hour par **/* per degreeFahrcnheit difference in temperature between the atr tnstde and outstde ofthe door, window, skylight or wall Section A. Windows and Skylights Section B. Solid. Wood Doorsbc Section C. Hollow Glass Block Walls Single V 1.13ac Double 0.45ae Triple 0.281ae Nominal Thickness Inches 1 m m m 2 2K 3 Actual Thickness Inches % lXt m .. m m 2ys 2Vs u Exposed Door 0.69 0.59 0.52 0.51 0.46 0.38 0.33 Description u Still Air Both Sides Smooth surface glass blocks 7% x 7H x 3J4 in- thick.-----Ribbed surface glass blocks 7 x 7? x 3K in. thick-- 0.40 0.38 u* With Glass Storm Door 0.42 0.38 0.35 0.35 0.32 0.28 0.25 u Still Air Inside 15 mph Outside 0.49 0.46 See Heating. Ventilating and Air Conditioning, by Harding and Willard, revised edition. 1932. tComDuted using C 1.15 for wood; fi "* 1.65 and / = 6.0. . ___, It is sufficiently accurate to use the same coefficient of transmission for doors containing thin wood P^ip as that of single panes of glass, namely, 1.13 Btu per hour per square foot per degree difference between inside and outside air temperatures. , __ . T , *These values may also be used with sufficient accuracy for wood storm doors. Neglect storm doors If loose and use values for exposed doors. .... Air spaces assumed to be in. or morenn width. isolated cases when conditions conducive to such condensation exist. The probability of condensation increases with the relative humidity or vapor pressure and with the temperature difference and, in the case of inter stitial condensation, decreases with the vapor resistance on the warm side of the wall. Condensation on interior building surfaces10 (surface condensation) may be eliminated by either reducing the relative humidity or by maintaining the interior surfaces at or above the dew-point temperature. Permissible relative humidities for various wall, roof or glass coefficients and tempera ture differences may be`determined from Fig. 2. The permissible relative humidity for any specific type of construction may be determined by first ascertaining the coefficient of transmission (Z7) of the construction and then locating this coefficient on the horizontal scale of Fig. 2. A vertical line drawn to the proper outside temperature curve and then to,., the left hand scale will indicate the permissible relative humidity for the conditions involved. The dotted line shown in Fig. 2 indicates the per missible relative humidity (64 per cent) if surface condensation is to be avoided, for a frame wall having a coefficient of 0.26 and for an outside temperature of --10 F. Condensation within the construction may likewise be prevented by eliminating the moisture at the source or by providing a barrier on the 'Permissible Relative Humidities in Humidified Buildings, by Paid D. Close (A.S.H.V.E. Journal Section. Heating. Piping and Air Conditioning. December. 1939. p. 766). 115