Document LKbK75oGkKwX5V7L8wOXEkpx7

124 CHAPTER 6 1946 Guide Table 4. Conductivities (k) and Conductances (C) Used in Calculating Heat Transmission Coefficients (/) in Tables 5 to 18 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. MATERIAL DESCRIPTION Conductivitt Conductance ( (O Resistance Per Inch For Thickness Listod (t) (u> AIR SPACES Vertical, in. or more In-width..--------- 1.10 0.46 0.91 2.17 EXTERIOR FINISHES (Frame Walls) . 12.50 2.27 1.28 1.28 0.08 0.44 0.78 0.78 INSULATING MATERIALS or animal hair, enclosed or open_________ -- Insulating Board...... :........... .................... Mineral Wool.--------- --------- Fiber made born rock, slag or glass------------- 0.27 0.30 0.33 0.27 0.48 -- 3.70 3.33 3.03 3170 2.08 ____ INTERIOR FINISHES _Composition Wallboard--------------------- % in. to H in. thick___ : ----... Gtpsum Board (H in.)---------- --------------Gtpsum Lath (H in.) and Plaster..! Insulating Board 04 in.)-- Insulating Board Lath 04 in.) and Insulating Board Lath (1 in.) and Metal Lath and Plaster....................... Plaster thickness assumed J4 Plaster thickness assumed Yt in.------------- Wood Lath and Plaster______ -- 0.50 3.30 ---- 3.70 ' 2.4 0.66 0.60. .0.31 4.40 2.12 t 2J0 2.00 0.30 -- 0.27 0.42 1.52 1.67 * . 3.18 0.23 0.47 0.40 MASONRY MATERIALS Adobe, assumed 4 in. thick.-- -- Por/TV Cement. Mortar. _____ :----------------- -- 3 in. Clat tile (hollow).......... 4 in. Clat tiu (hollow)--------6 in. Clat tils (hollow)--------8 in. Clat tilh (hollow)--------------10 in. Clat tile (hollow)....-- 12 in. Clat tile (hollow)-- 16 in. Clat ms (hollow)--------- 3 in. Concrete blocks.--.......------- 8 in. Concrete blocks.......... ii Sand and gravel aggregate........ ............. ... HoDow, cinder aggregate--------- ----------------HoDow, gravel aggregate ------- .....-- .... 12.Q0 "2io 12.00 12 in. Concrete blocks.......................... 8 in. Concrete blocks----- ----------------- . Gtpsum fiber concrete--............ Hollow, light weight aggregate*-------------.87M cent gypsum and 12)4 per eent 1.66 12.50 12.00 12.50, .0.89 1.25 ' 2^0 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 - 1.57 . 1.67 1.72 2.50 3.23 _ 0.78 1.00 1.00 1.25 1.66 1.88 2.00 2.13 . 1.64 2.18 . , ,, ______ "Conductance values for horizontal air spaces depend'on whether the heat flow is upward or downward, but In most cases it is sufficiently-accurate to use the same values for horizontal as for vertical air spaces. `Expanded slag, burned clay or pumice. ' ,, Heat Transmission Coefficients of Building Materials 125 Table 4. Conductivities (&) and Conductances (C) Used in Calculating Heat Transmission Coefficients (U) in Tables 5 to 18--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.' MATERIAL DESCRIPTION - CONDUCTTVITT OR Conductance w (C) Resistance Per Inch For Thickness Thickness lasted - (t) (hY ROOFING MATERIALS Built-up Roofing__ -I-,-,,-,,,.-............. Wood Sehnoles____ _________ __ SHEATHING INSULATING BOARD UV.) Fra or Yellow Pine (1 in.) Fib, pt.TM nnn.niNn paper SURFACES Ordinary non-reflective materials, vertical.... Ordinary non-reflective materials, vertical_ WOODS Fib sheathing (1 in.) building paper and Yellow Pine lap siding.______ Maple or Oak Yellow Ptnb or Fir io.bo E: 11 1.15 0.80 - 6.00 6.50 3.53 6.50 20.00 1.28 2.82 0.42 2.56 1.02 0.86 1.65 6.00 ' 0.50 po --- -- 057 1.25 0.17 0.1S 0.28 0.15 0.05 0.78 0.35 2.37 0.39 0.98 1.16 0.61 0.17 2.00 transmission U. of the insulated construction may be compared with the corresponding coefficient U without insulation. Attention is called to the necessity of applying the insulating material in accordance with the manufacturer's specification. The engineer must carefully evaluate the economic considerations involved in the selection of an insulating material as adapted to various building constructions. Lack of proper evaluation, or improper installation may lead to unsatisfactory results. Computed Heat Transmission Coefficients Computed over-all heat transmission coefficients of many common types of building construction are-given in Tables 5 to 18, inclusive, each coefficient being identified by a serial number except in Table 18. For example, the coefficient V of a brick-veneer, frame wall with wood sheathing and in. of. plaster on gypsum lath is 0.27, (Wall No. 28-C in Table 5) and with 2 in. of blanket or bat insulation .the coefficient would be 0.097 (No. 49-B in Table 6). Example 1. Calculate the coefficient of heat transmission U of a brick-veneer, frame wall with wood sheathing, building paper, and, V2 in. plaster on % in. gypsum lath, based on a wind exposure of 15 mph. Also calculate the coefficient when 2 in. of bat insulation is added, leaving an air space in the wall, and correcting for framing amounting to 15 per cent'of the. wall area. Solution: Starting from the exterior, the resistances making up the total heat resistance are (1) exterior surface,' (2) brick-veneer, (3) wood sheathing *56'in. thick and building paper,- (4) air space 3% in.- wide, (5) in. gypsum lath and plaster, (6) interior surface. Then using the values from Table 4 in Equation 4: -- 4- 1 4- ' 1 "1 1 ,1 ; 1 6.0 _r 2.27 `r 0.86 T 1.10 ^ 2.4 "r 1.65 - <