Solar reflectance index changes (for roofing materials) with age of materials – is it reasonable that the SRI might increase?
lrettew
| Posted in Green Products and Materials on
Looking at high(er) solar reflectance index shingles for a replacement residential roof in Maryland – generally, I would expect the SRI of the materials to stay the same or decrease slightly with age, but I’m seeing some products (at coolroofs.org) where the SRI actually increases at 3 years – is this reasonable?
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In general, cheap exterior paint "fades" when it is exposed to sunlight. Making pigments that stay dark and don't get "bleached" by sunlight exposure is difficult. So yes, it's reasonable that SRI goes up, because the color gets lighter. An off white or darker color might lighten to get closer to the reflectance of white, but a true bright white can only get worse, and a faded off white will never be as high as a new bright white.