Document jg5z4Y58OzVkxQb9Y5LeKbXek

u i: s r,!; : i':i; :a DMCWfflOS of Roof Construction* A.M. 10 12 rM. 10 12 Cooling Load 281 5. Corrections. For temperature difference when outdoor maximum design temperature minus-room is dif ferent from 15 deg. If the outdoor design temperature minus room temperature is different from the base of 15 deg, correct m follows: When the difference is greater (or less) than 15 deg add the excess to (or subtract the deficiency from) the above differentials. Pot outdoor daily range of temperature other than SO deg. If the daily range of temperature is less.than 20 deg, add 1 deg for every 2 deg lower daily range; if the daily range is greater than 20 aeg, substract 1 deg for every 2 deg higher daily range. For example, the daily range in Miami, Florida is 12 deg or 8 deg less than 20 deg, therefore, the correction is 4 deg at all hours of the day. Light Colors. Credit should not be taken for light colored roofs except where the permanence of the light color is established by experience, as in rural areas or where there is little smoke. When the exterior surface of roof exposed to the sun is a light color, such as white or aluminum (which absorb approximately 50 percent and reflect 50 percent of the solar radiation) add to the. temperature differential for roof in shade 55 percent of the difference between the roof in sun and roof in shade. When the roof exposed to the sun is a medium color such as light grey, blue or green, or bright red, add 80 percent of this difference. For solar transmission in latitudes other than 40 deg north, and in other months. The table values of tern* perature differentials will be approximately correct for a roof in the following months: 22"* GGyyppssuumm o-tr- 1' Insulation 12"" WWoooodd06 oorr , 1id- 4' Rock Wool 2' Concrete oriin Furred Ceiling 2* Gypsum j 44"' CCoonnccrreettee owrith 2' Insulation 6" . Concrete + ?' Insuulaaitiilotrnu l1 _________________ iR--o--o--t--s--C--o---v--e--e--e- EotwpomW11s0 tt0mS-lr-N----- ----------------- r _______ ---------------------- _i A +16i\ o2o2 \ 18 Light Construction Roof with 1* Water Heavy Construction Roof with V Water --4 10 14 0 6 10 Any Roof with 6' Water ---- e. TO St7N 12 18 1 16 2 8 12 10 6 6W 18 1 12 | 20 14 : , 10 roofs in Sbaoe 6 12 1 14 Light Construction MHeeadviuymCConosntsrutrcutciotinon | --2| -- aj 2 o0j 8 4 ( 12 .8 ( * Includes | in.felt roofing with or withoutslag. May also be used for shingle roof. 1---"" ' -- -- -- " 1 ^Nominal thickness'- , of the wood. --------------vnx> TABLE g NOTES FOR TABLE 9 r Total heat transmission from solar) f \ (Heat transnusswi at,x_puinaium.. rbaedtwiaetieonnoauntdsitdeemapnedrarotuormedaififre, reBnctuelf _ }/dEifqfeurievanlteianl ttferommpearbatouvree/I Ay mcoeerffiBeiteuntpfeorr (hr) per (hr) (aqft) of roof area ) (table ) [(sq ft) (F deg) 1. Source- Calculated by Mackey and Wright method (see reference list) and adjusted after studynff^ ASHVE original test data. Estimated for July in 40 deg north latitude. (For sol-air temperatures used calculations see Table 8.) For typical design day where the maximum outdoor temperature is 05 F minimum temperature at night is approximately 75 F (daily range of temperature, 20 F) mean 24 hr perature 84 F for a room temperature of 80 F. All roofs have been assumed a dark color which absorbs 2. Application. These values may be used for all normal air conditioning estimates; usually withp^ percent of solar radiation, and reflects only 10 percent. c5oerxrepclatiionns,hinowlattoituaddjeu0stdtehgetote5m0pdeergantuorrethdoifrfesoreunthtiawlhfoernoththeelroraodoims caanlcduolautteddofoorrttehmepheortatteusrtews.eather. - 'ft 3. Peaked Hoofs. If the roof is peaked and the heat gain is primarily due to solar radiation, use to? apreer4aa.otufArtethtiedcsirfo.feorfIe,fnthtthieaealcfroeearilianpgrrooijsoeficnetsxepudoloasnteedadthaoontrdhizeiofsnautfanalmnpliaasynuebs.ee'ddeincrteha eseadtt2ic5 for positive percent, ventilation, the total:t*|; .j Nobth Latitude Latitude (deg) Months 0 A11 Months 10 All Months 20 All Months except Nov, Dec. Jan 30 Mar, Apr, May, June,..July, Aug, Sept 40 April, May, June, July, Aug 60 May, June, July South Latitude Latitude (deg) Months 0 All Months 10 All Months 20 All Months except May, June. July 30 Sept, Oct, Nov, Dec, Jan. Feb. Mar . 40 Oct, Nov, Dec, Jan, Feb 50 Nov, Dec, Jan For other months, the total temperature differential (lx) may be approximated by the use of the following formula: tx tg + Uv -- tg) where la = temperature differential for the same roof in shade for desired time of day; obtained from Table fy = maximum solar transmission through glass, Btu per (hr) (sq ft) for flat skylight in July, 40 deg north latitude (Note: this is maximum value irrespective of time). ~ same as ly except use the maximum value for flat skylight, for month, and latitude desired for txtv ~ temperature differential for particular roof exposed to sun for the desired time of day from Table (Note that this makes adjustment only for solar radiation and that there may be additional correction for outtemperature.) air temperature t, is the temperature of the outdoor air, which, in the absence of all radiation exchanges, would give the same rate of heat entry mto the surface as would exist with the actual combination of incident solar radiation, radiant energy exchange with the sky and other outdoor sur roundings, and convective heat exchange with the outdoor air. The sol-air temperature data5'610 as developed by Mackey and Wright or an industrial atmosphere were used as a basis for preparing Table 8 snowing summer design sol-air temperatures. Sol-air temperatures may so be estimated from experimental observation of surface temperatures walls and roofs which appear in the literature.11-12 Both analytical and xpenmental studies have been made on the problem10 of heat flow through ** an(i roofs. Those concerned with a further study of the details of mu hfat* es^lraa*'es rn particular relation to periodic heat flow will find _ r? 01 value and interest in the reports of experimental studies of these P blems.10' . >2. i3, u, is The reader may also refer to the Cooling Load au(jPter The Guide 1952 for the theory of heat flow through walls llij mas rm