Document 0qKwbeNbN3VmJM70Q7nwXr3DR

HEATING VENTILATING AIR CONDITIONING CUIDE 1943 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: Brick veneer__________ 4 in. Plaster and metal lath.. % in. Plaster (on wood lath, plasterboard, rigid insulation, board form, or corkboard)..................1...................... in. Slate (roofing)_______________ _________ ____ ___ _____________ in. Stucco on wire mesh reinforcing_; 1 in. Tar and gravel or slag-surfaced built-up roofing.. 1-in. lumber (S-2-S)__ ____________1____ ;_______ 1^4-in. lumber (S-2-S)______________ ___________ 732 m. ..ljfe in. 2-in. lumber (S-2-S)________ ____ _________ ___ - \% in. 2J4-in. lumber (S-2-S).............................................. . - 2H in. 3-in. lumber (S-2-S)................................................... - 2j| in. 4-in. lumber (S-2-S).. .. 3% 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 use a minimum coefficient of 0.10 to allow for possible defects in workmanship, poor construction and other factors which would increase-the heat loss. The lower the theoretical wall or roof coefficient the greater will be the percentage of error due to construction defects or failure of the insulationr' to perform as rated. 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 coefficient of transmission of a top floor ceiling, unheated attic space, and pitched roof per square foot of ceiling area is: Ur x Ur* (4) where U = combined coefficient to be used with ceiling area. Ur -- coefficient of transmission of the roof. Utx -- coefficient of transmission of the ceiling. n = the ratio of the area of the roof to the area of the ceiling. In selecting the values to be used for Ut and Ur* it should be noted CHAPTER 4. HEAT TRANSMISSION COEFFICIENTS Table 2. Conductivities (ft) and Conductances (C) of Building Materials and Insulators3 The coefficients are expressed in Bin per hour per squarefoot per degree Fahrenheit per t in. thickness unless otherwise indicated. Material Description- D ensity (Lb per Cu Ft) s'es S CD Ss SB Igi E8 ea> u q Zo Zo OO -4 -|o 8 5 aht oBS Sn <Un 33 Pi 0 e* 3oH < masonry materials Tile or Tebrazzo....... ..... Typical fiber gypsum, 87.5% gypsum and Special-concrete made with an aggregate of Blast furnace slag aggregate.--------------------Expanded venniculite aggregate----------- Expanded venniculite aggregate---------------Expanded venniculite aggregate.--------------Expanded venniculite aggregate---------- -- 76 40.0 50.0 60.0 70.0 51.2 101.0 142.0 132.0 97.0 75.0 76.0 20 26.7 35 50 Hollow clay (2 in.) H-in. plaster both sides.. 120.0 Hollow clay (4 in.) >4-in- plaster both sides- 127.0 Hollow clay (6 in.) V$-in. plaster both aides- 124.3 Typical 'flooring--....- - ---- 51.8 75.6 75 " 75 75 75 75 . 74 70 75 75 75 75 70 90 90 90 90 110 100 105 70 76 -- 5.00* 9.20* 3.56* 5.009 12.00* 12;00* 11.35(0 16.36 2.5 1.06 1.44 1.80 2.18 1.66* 3.98 12.6 10.8 4.9 4.0 1.6 0.68 0.76 0.86 1.10 12.50 12.00 1.00 0.64 * 0.60 * 0.58 * 0.40 * 0.31 1.00 0.60 0.47 0.46 1.66 2.96 12.00 0.20 0.11 0.28 0.20 0.08 0.08 4.0 0.94 0.69 0.56 0.46 0.60 0.25 0.08 0.09 0.22 0.25 0.63 1.47 1.32 1.16 0.91 0.08 0.08 1.00 1.57 1.67 1.72 2.50 3.23 1.00' 1.67 2.13 2.18 0.60 0.34 0.08 _ (__2) (5) (3) (3) (3) (3) (3) (4) (3) l4! (4) (4) 41 (3) (3) U) (3) 1__3) ___ ___ --_ (2) (2) _12) (4) (4) 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, teste conducted at Armour Institute of Technology, based on samples submitted by manufacturers. . . , w. 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. 'Lees and Chariton. .. . . Recommended conductivities and conductances for computing heat transmission coefficients. fFor ibiVlrnpttg stated or used on construction, not per 1 in. thickness. For additional conductivity data see A-S.R.B. Data Book. ____ *If outside surface of block is painted with an impervious coat of paint, add 0.07 to resistance tor sand and gravel blocks. Add 0.18 to resistance for cinder blocks. Add 0.17 to resistance for burned clay aggie- ^^Recommended value. See Heating. Ventilating and Air Conditioning, by Harding and Willard, revised See A.S.H.V.E. Research Report No. 915--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 m the direction of heat How. I he 12-in. hollow tile is based on three cells in the direction of heat flow. The 16-in. hollow tde consists of one 10-in. and one 6-in. tile, each having two cells in the direction of heat flow. tRooffnTMaiSh!.' thick (1.34 lb per sq ft), covered with gravel (0.83 lb per 3q ft), combined thickness assumed 0.25. 97