Document evYQ08zQJ4NwGGOEow0B4Opxm

144 Chapter 7 1945 Guide -through. . A small amount is reflected and a portion is absorbed by the .glass. The amount absorbed depends upon the";haracter and thickness-- of the glass and'the angle between it and the sun's rays. The temperature of the glass is raised by the absorbed heat and this heat is then delivered to the air on each side in proportion to the difference between the glass and air temperatures7. The A.S.H.V.E. tests8 indicate that a single pane of double strength glass 0.127 in. thick absorbs approximately 11 per cent of the solar radiation passing through it when the impingement is normal. For smaller angles of impingement, the glass retards percentages of the total radiant energy approximately in proportion to the sine of the angle. Ig-^--j ______ 1 -Design temperature t---> Walls of Different Construction and Orientation on a 93 F Design Day with 90 per cent of Design Solar Radiation Walls BE, BS, BW and BN--12 in. solid brick and plaster facing east, south, west and north respectively. Walls TE, TS, TW and TN--4 in. brick veneer, 8 in. tile and plaster facing east, south, west and north respectively. Walls FE, FS and FW--4'tn. brick veneer, building paper, % in., matched sheathing, 2 z 4 in. studs, metal lath and plaster facing east, south and west respectively. The amount of solar radiation delivered to an unshaded glass surface may be obtained from Tables 2,3, 4 or 5. These values must be used only for the net glass area on which the sun shines and not the entire glass area. Tests at the A.S.H.V.E. Research Laboratory9 have determined the percentage of heat from solar radiation actually delivered to a room with various types of outdoor and indoor shading. The data in Table 7 are taken from these tests. The percentage values in this table were obtained by dividing the total amount of heat actually entering through the shaded window by the total amount of heat calculated to enter through a bare window (solar meat Absorbing Glass Windows, by W. W. Shaver (A.S.H.V.E. Transactions, Vol. 41, .1935, p. 287). A.S.H.V.E. Research Report No. 974--Radiation of Energy Through' Glass, by J. L. Blackshaw and F. C. Houghten (A.S.H.V.E. Transactions, Vol. 40,1934, p. 93). A.S.H.V.E. Research Report No. 975 --Studies of Solar Radiation Through Bare and Shaded Windows, by F. C. Houghten, Carl Gutberlet. and J. L. Blackshaw (A.S.H.V.E. Transactions, Vol. 40, 1934. p. 101). A.S.H.V.E. Research Report No. 1180--Heat Gain Through Western Windows With and Without Shading, by F. C. Houghten and David Shore (A.S.H.V.E. Transactions, Vol. 47, 1941. p. 251). Loc. Cit. Note 8. Cooling Load 145 Table 6. Time Lag in Transmission of Solar Radiation ________ :_________ Through Walls and Roofs Type and Thickness of Wall or Roof Time Lag, Hours 1- in. yellow pine horizontal roof,.water proofing, smooth black finish..... 2- in. yellow pine horizontal roof, water proofing, smooth black finish...... 4-in. reinforced clay tile horizontal roof, water proofing, slag finish_______ 2-in. gypsum horizontal roof, water proofing, slag finish___ ____________ Slate and slaters felt on 2 in. tongue and grooved yellow pine, sloped roof 4-in. gypsum horizontal roof, water proofing, slag finish___ _____________ 6-in. concrete horizontal roof, water proofing, slag finish______ 1-in. concrete, 4-in. cinders, 1J4-in. concrete, water proofing, smooth black finish.-__________________________ ------- ----------------------------------Wood siding, 1-in. sheathing, 2x4 studs, lath and plaster.______________ Wood siding, 1-in. sheathing, 2x4 studs (studding space filled with insula tion) lath and plaster____ _______________ :_________ ___________ 4-in. brick, 1-in. sheathing, 2x4 studs, lath and plaster. 4-in. brick, 8-in. tile and plaster__ ____ .-.___________ ____ 13-in. brick, plastered1.............................................................. ..................... 9-in. brick, 3%-in. tile, 5)^-in. air space, 3%-iri. tile and 13-^-in. plaster.... 1 m 2K 2H 2^ 5 8 2 5 7 10H 12 16 radiation plus glass transmission, based on observed outside glass tem perature). For bare windows on which the sun shines, the transmission of heat from outside air to glass may be small or negative as the' glass temperature is raised by the solar radiation absorbed. In calculating the total heat gain through windows on the sunny side of buildings, it is sufficiently accurate to proceed as outlined herewith: Consider the total heat gain as that resulting from solar radiation and neglect the heat transmission through the glass caused by the difference between the temperatures of the inside and outside air. This method should be used except at times when the calculated heat gain per square foot due to normal transmission exceeds the solar intensity. At such times, solar radiation may be neglected and the total heat gain considered as resulting from normal transmission. The. solar heat transmission through windows or skylights may be expressed by the formula: Hc = AajI 4 (2) where Ha = solar radiation transmitted through a window, Btu per hour. Ac = net area of glass exposed to sun's rays, square feet. / = percentage of solar radiation (expressed as a decimal) transmitted to the inside (Table 7). For bare windows, / = 1: I = intensity of solar radiation striking surface, Btu per hour per square foot (Tables 2, 3, 4 and 5). - Table 7. Solar Radiation Transmitted Through Shaded Windows Ttps or Appurtenance Fimas ' Faohg Sue Canvas awning................................ .............................. ........ ,, Plain Canvas awning.____________________ ________________ ____ Aluminum Inside shade, fully drawn____________ ___ _____ ____________ Aluminum Inside shade, one-half drawn................................................... .... Buff Inside Venetian blind, fully covering window, slats at 45 deg. Aluminum Outside Venetian blind, fully covering window, slats at 45 deg--- Aluminum Peb Cent Delivered to Boom 28 22 45 68 58 22