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During 1939, thirty-two manufacturers, representing about 95 percent of the asphalt-prepared roofing industry, produced 34,225,187 squares ^ of prepared roofing. Almost one third of this, 11,173,856 squares, was in the form of asphalt shingles, which are used principally for roofing dwellings.
In particular, temperatures greater than 199 °C (390 °F), were shown to produce a greater exposure risk than when bitumen was heated to lower temperatures, such as those typically used in asphalt pavement mix production and placement. [115]
Wintry temperatures cause the roof to shrink while warm temperatures make it expand. ... Low-quality asphalt shingles are especially at risk during temperature drops as they near the end of their ...
Roof orientation and ventilation can extend the service life of a roof by reducing temperatures. [13] Shingles should not be applied when temperatures are below 10 °C (50 °F), as each shingle must seal to the layer below it to form a monolithic structure. The underlying exposed asphalt must be softened by sunlight and heat to form a proper bond.
The underlayment also sheds any water which penetrates the roof covering from an ordinary leak, a leak from wind-driven rain or snow, wind damage to the roof covering, or ice dams. However, the application of underlays may increase the roof temperature, which is the leading cause of ageing of asphalt shingles. Not installing an underlay may ...
Originally asphalt roofing required a layer of gravel above it for two reasons. First, asphalt with direct exposure to sunlight degrades much faster, mainly due to the expansion and contraction throughout a day, and also the damage created by UV rays. Second, asphalt needs weight above to hold it down, because it sits on the top of a building ...
The pitch of the roof is in part determined by the roofing material available, a pitch of 3 in 12 (1:4) or greater slope generally being covered with asphalt shingles, wood shake, corrugated steel, slate or tile. The water repelled by the roof during a rainstorm is potentially damaging to the building that the roof protects.
As part of the new efforts, DOE will install a cool roof, whenever cost-effective over the lifetime of the roof, during construction of a new roof or the replacement of an old one at a DOE facility. In October 2013, the United States Department of Energy ranked Cool Roofs as a 53 out of 100 (0 to 100 weighted average) for a cost-effective ...