Asphalt shingles with their desirable aesthetics and proven
performance have been the steep-slope roofing material of choice in
the U.S. for more than half a century. According to "Residential
Roofing 2010: A Market Focused Update," published by Principia
Partners, Exton, Pa., more than 80 percent of sales in the U.S.
residential roofing market are asphalt shingles or bitumen-based
Shingles typically are constructed by coating a reinforcement
layer with molten bitumen and covering the surface with roofing
granules to protect the bitumen from harmful ultraviolet (UV)
radiation while providing desirable colors.
Roofing granules usually are made from naturally occurring
mineral particles that are translucent to UV radiation. However,
roofing granules typically have high absorption of solar heat, so
shingles tend to have low solar reflectance. As a result, asphalt
shingles can reach relatively high surface temperatures during hot
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