Document reQmDa1q1KJ3nKj86056rGMxr

308 CHAPTER 13 1957 Guide Table 11. Summer l' Coefficients of Heat Transmission U of Flat Roofs Covered With Built-Up Roofing* Btu per (hour) (square foot) (F deg difference between the air on the two sides) 'Insu--lat---i-o---n-- --on TTaobp nopp TD)eMc*X (Covered With Built-Up Roofing) Ttpe op Roop Deck Ceiling not shown Flat Metal Roof Deck Thickness op Roop Deck (Inches) 4 Ply Felt Roof No Ceiling-- Underside of Roof Furred Ceiling with Air Space. Metal Lath and Plaster No In sula tion 0.73 Insulating Board* No Thickness, In. In- i 1 2 tion ' 0.35 0.23 0.17 Q.13 0.40 I MM iHaUAUJA Thickness, " In. 1u 0 0.18 0.14 0. Ditto + 4 in. Slag 0.54 0.30 0.20 0.16 0.13 0.34 0 0.16 0.13 0. Precast Cement Tile Ply Felt Roof Ditto ,. + 4 in. Slag If 0.67 0.33 0.22 0.17 0.13 0.38 0 1 0.18 0.14 0. 0.50 0.28 0.20 0.15 0.12 0.32 C0.211 0.17 0.13 0 Concrete 4 Ply Felt Roof Ditto + 4 in. Slag 0.65 0.59 0.54 0.33 0.31 0.30 0.22 0.21 0.20 0.16 0.16 0.16 0.13 0.13 0.13 0.37 0.36 0.33 0.49 0.46 0.42 0.28 0.20 0.15 0.12 0.31 0.27 0.19 0.15 0.12 0.30 0.26 0.19 0.14 0.12 0.29 4 0.18 0.14 0 3 0.17 0.13 C 2 0.17 0.13 0 1 0.16 0.13 0 i o.ie 0.13 ( >0 0.16 0.13 [0.10 Gypsum and Wood Fiberb 4 Piy on 4' Gypsum Board Felt Roof 2] 3i Ditto 24 4 in. Slag 34 0.23 0.17 0.13 0.12 0.25 0.2C 0.16 0.12 0.11 0.21 0.2C 0.1C 0.13 0.1 0.22 0.1* 0.14 0.12 0.1C 0.19 18 16 0.14 0.13 0.12 C O.llC 16 0.12 0.11 ( i5 o.i: 0.10 Wood0 4 Ply Felt Roof 1 14 2 3 1 Ditto H 4 i* Slag 2 3 3 9 0.2 0 0.22 0.2 0 0.1 9 0.1 r 0.1 1 0.1 5 0.1 [ 0.1 t 0.1 2 0.1 i 0.1 L 0.29 0.24 0.22 2 0-16 0.13 0.1 1 0.09 0.17 55 0.23 0.1 7 0.14 0.1 1 0.25 4 0.20 0.1 5 0.1 2 0.1 A 1 0.191 0.141 0.12| 0. 0 0.20 0 0.15| 0.12| 0.10| 0.019 0.16 20 0.1 5 0.13 18 0.1 1 0.12 16 0.1 3 0.11 13 0.12 0.10 * The summer coefficients are considered temporary, and have been calculated with an outdoor wind velocity of 8 mph. For summer an inside surface conductance of 1.2 has been used instead of the 1.65 value. In all of these roofs a 4 ply felt roof has been assumed I in. thick, thermal conductivity TM Pitch and slag have been assumed as an additional thickness of 4 in. which has been assigned thermal 0**' du'cbti8v7i4type=rc1e.0n.t gIynpsbuomth, 1c2a4sepsethrceernmt awlocoodnfdibuecrt:iviTtyhricekfenresstsoinodniecaintcehd tihnicclkundeesss4. in. gypsum board. Tbfe is acpNouormedinraolothf.ickness of wood is specified, but actual thickness was used in calculations. d If corkboard insulation is used, the coefficient U may be decreased 10 percent. ' A method of determining heat flow rates, when structure is not given 111 Tables 9 or 10, is illustrated in Example 7. Example 7: A 4 in. stone concrete root covered with an average depth of 4 in. cur der concrete (k -- 4.9) on which is placed a f in. thick felt roof with | in. pitch and sWs surface, is exposed to the sun. The location is the central part of the United States-. Cooling Load 309 Design temperatures are: outdoor 95 F; daily range 20 deg; indoor temperature 80 F. Find the heat flow rate at 2:00 p.m. for a day in July. Soiuiiun. For the purpose of selecting the equivalent temperature differential, this construction is assumed to be equal approximately to an uninsulated 6 in. concrete roof, for which the equivalent temperature is found to be 38 deg in the 2:00 p.m. column of Table 9. Calculate the overall heat transmission coefficient U (see Equa tion 3 of Chapter 9) of the roof as follows : U =----------------------- 1----------------------- = 0.33. -1- 4 , 4 0.-3-7-5---. -0--.5-0-----1-- 12 12 4.9 1.33 1.00 4.0 The heat flow rate is then 38 X 0.33 equals 12.5 Btu per (hr) (sq ft). SUN SURROUNDING^/ INOOOftS TRANSMITTED OUTDOOR RADIATION (wave LENGTHS UNCHANGED JRANSMTTTEP INDOOR RADIATION 0*AYg LENGTHS UNCHANCED) INCIDENT INDOOR RADIATION REFLECTED INDOOR OUTDOOR CONVECTION *>*.h>< V THERMAL CAPACITANCE Of CLASS INDOOR CONVECTION V<u 'S*>h EMITTED OUTDOOR radiation (DIFFERENT DISTRIBUTION OF ENERGY vs. WAVE LENGTH then transmitted) EMITTED INDOOR RADIATION [(DIFFERENT DISTRIBUTION Of ENERGY VS.WAVC LENGTH -tt* a*--yf-- THEN TRANSMITTED) t - OUTDOOR AIR TEMPERATURE * OUTDOOR CLASS - SURFACE TEMPERATURE tl -- INDOOR AIR TEMPERATURE tgl*w INDOOR GLASS--SURFACE TEMPERATURE Fig. 2. Instantaneous Heat-Balance Conditions on a Glass Section TABLES FOR CALCULATING SOLAR HEAT GAIN THROUGH GLASS AREAS Basic Principles th^n *er *;o se* forth the principles involved in calculating, heat flow through glass areas, the general instantaneous heat-balance relation will .Presented. It will be shown schematically in Fig. 2. The net heat am fr the indoor space is the result of several contributing phenomena, onie observations concerning the behavior of glass with respect to radiant ergy will lead to a better understanding of the heat-balance relation. 0 pQVanous degrees glass transmits radiation having wave lengths between and ^5 microns. Of the portion not transmitted, part is absorbed, abs h-6 remain(fer is reflected. Outside these limits, glass is opaque, ne ?.r .J^S approximately 94 percent and reflecting 6 percent.. Only, a length l amount of radiant energy from a surface at 450 F has a wave form * or**r t-han 4.75 microns. It is therefore convenient to treat all 17118 of solar radiant energy separately from radiant energy from other