Document K5Qp0jekQbMbwwqvYdbnK3N

Heating Ventilating Air Conditioning Guide 1938 properly installed. The architect or engineer must carefully evaluate the economic considerations involved in the selection of an insulating material as adapted to various building constructions. Lack of good judgment in the intelligent choice of an insulating material, or its improper installation; frequently represents the difference between good or unsatisfactory results. Refer to Chapter 7 for a discussion of wall condensation. Computed Transmission Coefficients Computed heat transmission coefficients of many common types of building construction are given in Tables 3 to 13i inclusive, each con struction being identified by a serial number. For example, the coefficient of transmission (/) of an 8-in. brick wall and 34 in. of piaster 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 'A in. of plaster applied directly to the interior surface, based on an outside wind exposure of 15 mph. It is assumed that the outside course is of hard (high density) brick having a 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 plaster is assumed to be 3.3, and the inside and outside surface coefficients are assumed to average 1.65 and 6.00, respectively, for still air and a 15 mph wind velocity. Solution, k (hard high density brick) = 9.20; x = i.O in.; k (common low density brick) = 5.0; x = 4.0 in.'; k (plaster) = 3.3; x -- A in.;/i = 1.65;/o = 6.0. Therefore. 1 4.0 ^0 6.0 + 9.20 + 5.0 0. 3.31 + 1 1.65 1 0.167 + 0.435 + 0.80 4- 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 those shown in Example 1, using Fundamental. Formulae .3, 4 and .5 and the values of k (or C),f;, fa 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 ,(/i) 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: V = 1 = 0.48 Btu per hour per square foot per degree difference 1 1.65 +1 0.781 0.80 1 6.0 12.62 in temperature between the ground and the air immediately above the floor. Rigid insulation refers to the so-called board form which may be used 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 96 Chapter 5. Heat Transmission Coefficients and Tables Table 2 Conductivities (k) and Conductances (C) of Building Materials and Insulators3 /founts are expressed in Bln per hour per square fool per degree Fahrenheit per 1 in. thickness. 1 he coejjto*TM-* r unless otherunse indicated. C o n d u c t iv it y (A) OR ( 0 Conductance | A utho rity j Material Sard and Grayed, Description Fine Coarse Cement Aggre gate Aggre gate Slump 0-No. 4 No. 4-M Per Cent Voids 1 2.00 2.75 0 11.5 1 2.75 4.50 0 10.9 1 3.50 5.50 0 11.2 1 2.00 2.75 5 13.9 1 2.00 2.75 5 13.9 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 S 14.7 O O BaS5 Ba, 144.7 145.7 144.5 142.5 142.5 141.1 141.1 139.2 139.2 -I-* -|o sS eIjlsS E1 |gI I& 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 12.8S 12.50 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 4) (4) (4) (4) 4) (4) (4) (4) (4) Avg. Value for Sand and Gravel Concrete___ 142.3 12.62* 1 2.00 2.75 0 16.6 135.3 74.87 11.20 0.09 (4) 1 2.75 4.50 0 15.4 137.8 75.18 12.00 0.08 (4) 3.50 5.50 0 16.3 136.4 74.75 11.50 0.09 W 1 2.00' 2.75 3 20.9 130.1 74.85 10.50 0.10 (4) 1 2.75 4.50 3 23.4 126.0 74.45 10.00 0.10 (4) 1 3.50 5.50 3 23.4 127.3 75.26 9.79 0.10 (4) Avg. Value for Limestone Concrete _ 132.15 -- 10.83 -- - . Hatdite_____ j 2.00 2.75 . 0 18.2 103;6 1 2.75 4.50 0 19.9 98.7 3.50 5.50 0 21.4 92.0 1 2.00 2.75 3 22.8 101.4 1 2.75 4.SO 3 26.0 94.0 1 3.50 5.SO 3 24.4 94.4 Avg. Value for Cinder Concrete _. _ -- 97.35 l 1 2.00 2.75 2.75 4.50 0 18.0 0 19.8 80.7 75.0 1 3.50 5.50 0 21.8 71.7 1 2.00 2.75 4 21.2 78.8 1 2.75 4.SO 4 22.2 72.4 2.75 4.50 4 22.2 72.4 1 3.50 5.50 4 23.9 71.0 75.26 75.71 75.72 74.95 75.20 75.55 74.82 75.75 74.82 74.76 75.39 75.49 75.46 4.63 4.30 3.73 4.89 4.38 4.24 4.86 4.15 3.78 3.67 4.38 3.89 3.86 4.00 0.22 0.23 0.27 0.20 0.23 0.24 -- 0.25 0.26 0.27 0.23 0.26 0.26 0.25 !4> (4) S4> (4) - (4) (4) (4) (4) (4) (4) (4) Avg. Value for Haydite ------ 74.57 3.96 -- _ Authorities: #>U. S. Bureau of Standards, tests based on samples submitted by manufacturers. 'A. 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. ^A.S.H.V.E. Research Laboratory. E. A. Allcut, tests conducted at the University of Toronto. rLees and Charlton. *0. B. Wilkes, tests conducted at the Massachusetts Institute of Technology. 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 Data Book. `If outside surface of block is paints 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.S.H.V.E. Transactions, Vol. 38. 1932. p. 47). 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. /Not compressed. Roofing, 0.15-in. thick (1.34 lb per sq ft), covered with gravel (0.83 lb per sq ft), combined thickness assumed 0.25. `Surface values were obtained on vertical surfaces and varying with the'temperature differences. A foil lined air space in a horizontal position will have a coefficient roughly three times greater if the heat flow is upward rather than downward. 97 /