Document 4Dq4BvRaVnVe397V5VJgO6OG

HEATINC VENTILATING AIR CONDITIONING GUIDE 1941 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 - --------------- ---------------- = 0.48 Btu per hour per square foot per degree difference 1 0.781 6.0 1.65 + 0.80 + 12.0 in temperature between the ground and the air immediately above the floor. Rigid insulation refers to so-called insulating board 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 it is probable that the values of U for these two types of roofs will compare favorably. The thicknesses upon which the coefficients in Tables 3 to 13 inclusive, are based are as follows: Brick veneer... ....... ........ 4 in. Plaster and metal lath.... 54 in. Plaster (on wood lath, plasterboard, rigid insulation, board form, or corkboard).... 54 in. Slate (roofing).. 54 in. Stucco on wire mesh reinforcing__________________ .. 1 in. Tar and gravel or slag-surfaced built-up roofing____ - % in. 1- in. lumber (S-2-S)______________ ______ ______ _ -25fi2 in. 1 J^-in. lumber (S-2-S)___________________ ___ ____ -1546 in. 2- in. lumber (S-2-S) 2 J4-in. lumber (S-2-S)___________ - 1H in. - 2% in. 3-in. lumber (S-2-S)_____________ .. 25| in. 4-in. lumber (S-2-S)_________ ____ .. 35| in. Finish flooring (maple or oak)____ Solid brick walls are based on 4 in. hard brick (high density) and the remainder common brick (low density). Stucco is assumed to be 1 in. thick on masonry walls. Where metal lath and plaster are specified, the metal lath is neglected. The coefficients of transmission of the pitched roofs in Table 12 apply where the roof is over a heated attic or top floor so the heat passes directly through the roof structure including whatever finish is applied to the underside of the roof rafters. It is the practice of many engineers in calculating heat losses to allow for possible defects in workmanship, poor construction and other factors which would diminish the efficiency of the insulation. The lower the theoretical wall or roof coefficient the greater will be the percentage of error due to construction defects. Combined Coefficients of Transmission If the attic is unheated, the roof structure and ceiling of the top floor must both be taken into consideration, and the combined coefficient of transmission determined. The formula for calculating the combined 78 CHAPTER 3. HEAT TRANSMISSION COEFFICIENTS AND TABLES Table 2. Conductivities (k) and Conductances (C) of Building Materials and Insulators3 ,, mMcienls are expressed in Bin per hour per square foot per degree Fahrenheit per t in. thickness i tie eoejj unless otherwise indicated. Material Description D U fEac OaaS, H* od ag 3 5s a sB S' G -i* -i |gl Tj 1S s s& P o OO gg taoa <% MASONRY MATERIALS Brick------- --------- -- 5.00* 9.20* 0.20 o.n 3.S6* 0.28 5.00* 0.20 12.00* 0.08 CONCRETE...... ........................ Typical Various ages and mixes*__________________ 12.00* 0.08 11.35 to 16.36 40.0 75 1.06 0.94 50.0 75 1.44 0.69 60.0 75 1.80 0.56 70.0 75 2.18 0.46 Typical fiber gypsum, 87-5% gypsum and 51.2 74 1.66* 0.60 Special concrete made with an aggregate of 101.0 70 3.98 0.25 142.0 75 12.6 0.08 Limestone.______________________________ 132.0 75 10.8 0.09 97.0 75 4.9 0.22 75.0 75 4.0 0.25 Blast furnace slag aggregate____ :_________ 76.0 70 1.6 0.63 Expanded vermiculite aggregate.__________ 20 90 0.68 1.47 Expanded vermiculite aggregate--___ _____ 26.7 90 0.76 1.32 Expanded vermiculite aggregate-- ______ 35 90 0.86 1.16 Expanded vermiculite aggregate______ ___ _ . 50 90 1.10 0.91 12.50* 0.08 12.00* 0.08 l.OOf* 1.00 0.64f 1.57 0.60f* 1.67 0.58f* 1.72 0.40f* 2.50 0.31f* 3.23 Hollow clay (2 in.) &in. plaster both sides.. 120.0 110 l.OOf 1.00 Hollow clay (4 in.) H-in. plaster both sides. 127.0 100 0.60f 1.67 Hollow clay (6 in.) plaster both sides. 124.3 105 0.47t 2.13 0.46t* 2.18 51.8 70 1.66 0.60 75.6 76 2.96 0.34 Tils oa Terrazzo____________ 12.00* 0.08 (2) (5) (3) (3) (3) (3) (4) (3) (4) 8} (4) (3) (3) (3) (3) (3) (2) (2) (2) (4) (4) Authorities: tU. 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. *Lee9 and Charlton.' Recommended conductivities and conductances for computing heat transmission coefficients. fFor thickness stated or used on construction, not per 1 in. thickness. For additional conductivity data see A-S.R.E. Data Book. `If 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 burned clay aggre gate blocks. `Recommended value. See Heating, Ventilating and Air Conditioning, by Harding and Willard, revisededition, 1932. *See A.S.H.V.E. Research Report No. 915--Conductivity of Concrete, by F. C. Houghten and Car! 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 inthe 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 10in. 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. 79 1 A-