How You Can Benefit from a Cool Roof

Learn how cool roof designs are used to reduce the heat absorption of conventional roofs and how they can help save money on your electric bill.

| May 2019


Cool roofs are designed to absorb less heat than conventional roofs. This mainly involves making them more reflective, through the use of lighter colors. However, new technologies also aim to produce surfacing materials with thermal emittance, or the ability to give off absorbed heat more quickly. The ultimate goal is to reduce surface temperatures and hold onto less heat during the day, which means less heat radiated from the surface at night.

Conventional shingle, asphalt, and tile roofs can be 55-85 degrees Fahrenheit hotter than the air, while cool roofs tend to be only 10-20 degrees Fahrenheit hotter. And while traditional roof surfaces may absorb 85-95% of the energy that reaches them, the coolest cool roof materials can reduce that rate to 35%, substantially lowering the amount of heat that is transmitted into a building.

Both low-sloped and steep-sloped roofs can benefit from cool roofing techniques, but each type needs a different approach.

Low-sloped roofs may be flat or have a maximum pitch of 2 inches of vertical rise in 12 inches of run (2:12). These roofs are most commonly found on commercial and industrial buildings and sometimes on apartment buildings, but rarely on homes. In the past, this type of roof would often be waterproofed with thick liquid asphalt that was either painted or sprayed on.

Two types of cool roof materials can be used to replace this asphalt: elastomeric coatings that are sprayed on, or flexible sheeting that is laid on the roof with seams that are glued, taped, or heat-sealed. Both are manufactured to have both high reflectivity and high thermal emittance. Most cool roof programs tend to focus on the low-sloped sector of the roofing world.

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