Document gDOnDEY33XN1RM0JZdwYOww4a

American Society of Heating and Ventilating Engineers Guide, 1937 properly installed. Besides the thermal conductivity there are sikJj properties as resistance to rot, vermine and fire which should be con. sidered in making comparisons. Computed Transmission Coefficients Computed heat transmission coefficients of many common types o[ building construction are given in Tables 3 to 13, inclusive, each construction being identified by a serial number. For example, the coefficient of transmission (U) of an 8-in. brick wall and in. of plaster is 0.46, and the number assigned to a wall of this construction is 1-B, Table 3. Example 1. Calculate the coefficient of transmission (U) of an 8-in. brick wall with in. of plaster applied directly to the interior surface, based on an outside wind exposurt of 15 mph. It is assumed that the outside course is of hard (high density) brick havinga conductivity of 9.20, and that the inside course is of common (low density) brick having a conductivity of 5.0, the thicknesses each being 4 in. The conductivity of the plasters assumed to be 3.3, and the inside and outside surface coefficients are assumed to averagt 1.65 and 6.00, respectively, for still air and a 15 mph wind velocity. Solution, h (hard high density brick) = 9.20; x = 4.0 in.; k (common low density brick) = 5.0; * = 4.0 in.; k (plaster) = 3.3; x = H in.;/i = 1.65;/o = 6.0. Therefore, 1 4.0 4.0 ,0.5 1 . 6.0 + 9.20 + 5.0 + 3.3 + 1.65 1 0.167 + 0.435 + 0.80 + 0.152 + 0.606 = 0.46 Btu per hour per square foot per degree Fahrenheit difference in tempera ture between the air on the two sides. The coefficients in the tables were determined by calculations similar to chose shown in Example 1, using Fundamental Formulae 3, 4 and 5 and the values of k (or C), ft, /0 and a indicated in Table 2 by asterisks. In. computing heat transmission coefficients of floors laid directly on the ground (Table 10), only one surface coefficient (ft) is used. For example, the value of U for a 1-in. yellow pine floor (actual thickness, 25/32 in.) placed directly on 6-in. concrete on the ground, is determined as follows: U = --------------- ---------------- = 0.48 Btu per hour per square foot per degree differenct \_ , 0.781 , 6XL . 1.65 + 0.80 + 12.0 in temperature between the ground and the air immediately above the floor. Rigid insulation refers to the so-called board form which may be usd structurally, such as for sheathing. Flexible insulation refers to the blankets, quilts or semi-rigid types of insulation. Actual thicknesses of lumber are used in the computations rather than nominal thicknesses. The computations for wood shingle roofs applied over wood stripping are based on 1 by 4 in. wood strips, spaced 2 in. apart Since no reliable figures are available concerning the conductivity of Spanish and French clay roofing tile, of which there are many varieties, the figures for such types of roofs were taken the same as for slate roofs, as it is probable that the values of U for these two types of roofs wii compare favorably. 106 Chapter. 5--Heat Transmission Coefficients and Tables Table 2. Conductivities (k) and Conductances' (C) of Building 1' Materials and Insulators3 art expressed in Btu per hour per square foot per degree Fahrenheit per 1 in. thickness. The coefficient unless otherwise indicated. ) / \ Resistivity ( y ) Material rt iTT-f Description Cement Fine Coarse Aggre gate Aggre gate Slump 0-No. 4 No. 4-M Per Cent .Voids 1 2.00 2.75 0 11.5 2.75 4.50 0 10.9 1 3.50 5.50 0 11.2 1 2.00 2.75 5 13.9 i 2.00 2.7S 5 13.9 1 2.75 ' 4.50 5 14.6 1 2.75 4.50 5 14.6 1 3.50 5.50 5 14.7 1 3.50 5.50 5 14.7 D ensity (L b per Cu F t) s is 5 |S| 2o Iasw s oo OO 144.7 145.7 144.5 142.5 142.5 141.1 141.1 139.2 139.2 75.06 74.77 75.00 75.50 74:74 73.30 74.89 74.50 75.15 13.10 12.90 13.20 12.10 12.40 12.40 12.10 12.85 12.50 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 R e s R ista 1 nc e 1 SO 1. <2 (4) (4) 4) (4) (4) (4) 4) (4) 14) Avg. Value for Sand and Gravel Concrete____ 142.3 -- , 1 1 1 1 1 2.00 2.75 0 16.6 135.3 2.75 4.50 0 15.4 137.8 3.50 5.50 0 16.3 136.4 2.00 2.75 3 20.9 130.1 2.75 4.50 3 23.4 126.0 3.50 5.50 3 23.4 127.3 -- '12.62 74.87 75.18 74.75 74.85 74.45 75.26 11.20 12.00 11.50 10.50 10.00 9.79 --- 0.09 0.08 0.09 0.10 0.10 0.10 - (4) (4) (4) (4) 4) (4) Avg. Value for Limestone Concrete - ------------ - 132.15 -- 10.83 -- - l 2.00 2.75 0 18.2 103.6 75.26 4.63 0.22 (4) 1 2.75 4.50 0 19.9 98.7 75.71 4.30 0.23 (4) 1 3.50 5:50 0 21.4 92.0 75.72 3.7$ 0.27 (4) 1 2.00 2.75 3 22.8 101.4 74.95 4.89 0.20 (4) 1 2.75 4.50 3 26.0 94.0 75.20 4.38 0.23 (4) 1 3.50 5.50 3 24.4 94.4 75.55 4.24 0.24 (4) Avg. Value for Cinder Concrete____ -- 97.35 4.86 -- - Haydite ____ . 1 2.00 2.75 0 18.0 80.7 74.82 4.15 0.25 (4) 1 2.7S 4.50 0 19.8 75.0 75.75 3.78 0.26 (4) 1 3.50 5.50 0 21.8 71.7 74.82 3.67 0.27 (4) 1 2.00 2.75 4 21.2 78.8 74.76 4.38 0.23 (4) 1 2.75 4.50 4 22.2 72.4 75.39 3.89 0.26 (4) 1 2.75 4.50 4 22.2 72.4 75.49 3.86 0.26 (4) 1 3.50 5.50 4 23.9 71.0 75.46 4.00 .0.25 (4) Avg. Value for Haydite_____ 74.57 _______ 3^96 _____ -- Authorities: 'U. S. Bureau of Standards, tests based on samples submitted by manufacturers. 5A. C. Willard, L. C. Lichty, and L. A. Harding, tests conducted at the University of Illinois. *J- C. Peebles, tests conducted at Armour Institute of Technology, based on samples submitted by manufacturers. 4F. B. Rowley, tests conducted at the University of Minnesota. JA.S.H.V.E. Research Laboratory. E. A. Allcut, tests conducted at the University of Toronto. rLees and Charlton. Recommended conductivities and conductances for computing heat transmission coefficients, tFor thickness stated or used on construction, not per 1-in. thickness. For additional conductivity data see Chapters 3 and 15, 1937 A.R.E. Data Book. Mf outside surface of block is painted with an impervious coat of paint, add 0.07 to resistance for sand and gravel blocks. Add 0.18 to resistance for cinder blocks. Add 0.17 to resistance for haydite blocks. 'Recommended value. See Heating, Ventilating and Air Conditioning, by Harding and Willard, revised edition. 1932. .. -See A.S.H.V.E. Research Paper, Conductivity of Concrete, by F. C. Houghten and Carl Gutberlet (A.b.H.V.E. Transactions, Vol. 38, 1932). The 6-in., 8-in., and 10-in. hollow tile figures are based on two cells in the direction of heat flow. The 12-in. hollow tile is based on three cells in the direction of heat flow. The'16-in. hollow tile consists of one 10-in. and one 6-in. tile, each having two cells in the direction of heat flow. /.\:ot compressed. assumed^) ^ SQ ft), covered with gravel (0.83 lb per sq ft), combined thickness 107