Increased Roof Life

Hotter roofs have shorter lives -- the effects of degradation from thermal expansion and contraction are well documented.  Roofs that are cooler will experience less temperature differential during the day, resulting in less stress from thermal expansion and contraction.  Metal roofs exhibit better performance than most other roofing materials because the standing seam roof system utilizes a sliding clip design that allows the roof to expand and contract without a stress build-up.  Couple that ability with a cool paint color and you have a system that not only is sustainable for as much as twenty to thirty years, but is guaranteed to maintain performance for at least 20 years by many manufacturers.

Some purportedly “cool” roof systems are especially prone to dirt collection, algal or fungal growth, and staining from acid rain and other environmental effects, not to mention UV degradation.  The dirtier these roofs become, the more emittance and reflectance performance is compromised and the hotter they become.  As the roof surface becomes hotter, these contaminants actually bake into the roof surface making it even harder to clean.  Cool roofs are usually made of light-colored materials, and if they don’t remain light they won’t remain cool. 

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Source: http://www.mbma.com/display.cfm?p=D0D8B611-6361-46A6-8C44BDDBC0F586F3