A cool roof is one that reflects the sun’s heat and emits absorbed radiation back into the atmosphere. The roof literally stays cooler and reduces the amount of heat transferred to the building below, keeping the building a cooler and more constant temperature. Imagine wearing a white or a black T-shirt on a hot day. By wearing the white T-shirt you will remain cooler than if you wore a black T-shirt because it reflects more sunlight and absorbs less heat. Cool roofs like a white T-shirt, keep the internal temperature of the building cooler.
However, a cool roof need not be white. There are many “cool color” products which use darker-colored pigments that are highly reflective in the near infrared (non-visible) portion of the solar spectrum. With “cool color” technologies there are roofs that come in a wide variety of colors and still maintain a high solar reflectance.
The two basic characteristics that determine the ‘coolness’ of a roof are solar reflectance (SR) and thermal emittance (TE). Both properties are rated on a scale from 0 to 1, where 1 is the most reflective or emissive.
The CRRC measures these two properties for roofing products, both for the product’s initial values and after three years of weather exposure. The CRRC publishes the results on the online Rated Products Directory. The online Directory is available to the general public at no charge, and it allows you to compare the rated values of various product types and brands.
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