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Solar heating, radiative cooling and thermal movement - Their effects on built up roofing

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Abstract
Twenty different built-up roof construction specimens, covered with five surfacing materials, were subjected to natural solar heating and nighttime cooling. The temperature and temperature changes observed during winter and summer exposures are discussed. The data indicate that the temperature attained in a roof membrane is influenced by the absorptance and emissivity of the surface as well as the thermal and physical properties of the substrate to which the roofing is applied. The data show that roofings placed over insulation may be heated to a temperature of 80 F above ambient due to solar heating and may be cooled as much as 20 F below the ambient due to radiative cooling. The thermal movements that occur in the components of a roof system due to temperature change are discussed in relation to built up performance and failures. Thermal expansion data are presented for some composite bituminous membranes. The data show that these membranes undergo greater thermal movements than most other components of a roof system and the rate of expansion is not linear but decreases as the temperature is increased.
Date
12/1963
Author(s)
William Cullen
Page(s)
33
Keyword(s)
solar heating; radiative cooling; thermal movement


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