Mediterranean have used them for many centuries . . . and in modern
times building researchers are quantifying their benefits. Now
California's new Title 24 standards offer credit for them-It's time
to take another look at cool, reflective roofs that can improve our
communities and the environment in the future.
What Makes a Roof "Cool"?
According to the new Title 24 coolroof standards, concrete tile
and clay tile roofs must have a minimum initial total solar
reflectance of 0.40. All other products must have a minimum initial
total solar reflectance of 0.70 when tested according to ASTM E903
or E1918. For purposes of calculating credit for a cool roof under
both the performance and prescriptive methods, a roof that meets
these criteria reduces heat gain through the roof by 36 percent. Of
course, the impact of this reduction on energy usage will depend on
the aspect ratio of the roof: a large, single-story warehouse will
have a larger roof area than a high-rise office building with a
smaller footprint.
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offers design assistance and incentives to design teams and building owners in California
to encourage high-performance nonresidential building design and construction.
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