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HEATING VENTILATING AIR CONDITIONING GUIDE 1944
Table 14. Coefficients of Transmission (U) of Flat Roofs Covered with Built-up Roofing. With Lath and Plaster Ceilings3'
(See Table 13 for Flat Roofs, with no Ceilings)
These coefficients are expressed in Btu per hour per square foot per degree Fahrenheit difference in temperature between the atr on the two sides, and are, based on an outside wind velocity of 15 mfih.
TYPE OF ROOF DECK
Roof Deck (Inches)
No Insula
tion
INSULATION ON TOP OF DECK . (Covered with Built-Up Roofing)
Insclatinq Board (Thickness Below)
CORKBOABD (Thickness Below)
M In. 1 In. 1M In-
1H In.
Flat Metal Roof Deck
tnjouT ion,
RPQTMK <?a
/
m
VtI ..........1
0.19
0.11
Precast Cement Tile RetFiNtf. /?alI
'^t/vrtoxTsJr . ctn-mc'
1M in.
Concrete lN/OLATtOM;
R-OCFlfla^ ^ /
2 in. 4 in.
cetunfi/
Gypsum and Wood Fiber* on'H in. Gypsum Board
2in/ULAtlO,
t-lDFiHG,
Cirjif :*.***: PLA/TpR. btk\L9'
2H in. 3Him
0.26 0.19 0.42 0.26 0.19 0.15 0.12 0.18 0J4 0.11 0.40 0.25 0.18 0.14 0.12 0.17 0.13 0.11 0.37 0.24 0.18 0:14 0.11 0.17 0.13 0.11
0.27 0.23
0.19 0.17
0.15 0.14
0.12 0.11
0.10 0.14 0.097 0.13
0.12 0.11
0.097 0.091
Wood* ROOFirf^j
1 in.
1M in. 2 in. 3 in.
0.21 0.16 0.13 0.11 0.15 0.12 0.10
0.26 o54
0.19 0.17
0.15 0.14
0.12 0.11
0.10 0.14 0.097 0.13
0.11 0.11
0.095 0.092
0.18 0.14 0.12 0.10 0.087 0.11
.. basfd n metal lath and plaster ceilings, but coefficients may be used with sufficient accuracy for gypsum lath or wood lath and plaster ceilings. It is assumed that there is an air space between ^ the under side of the roof deck and the upper side of the ceiling.
`87K per cent gypsum, 12K per cent wood fiber. Thickness indicated includes' H in. gypsum board. Nominal thicknesses specified- -actual thicknesses use(i in calculations.
112
T able 15. Coefficients of T ransmission U) of Pitched Roofs -(
Coefficients
are expressed in B tu between the a ir 'on
per hour per the two sides
square foot Per degree Fahrenheit and are based on a w in d velocity
doifff1er5enmcpeh.in
temperature
CHAPTER 4. HEAT TRANSMISSION COEFFICIENTS
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