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What if roofing could help reduce urban heat islands?

October 1, 2019

Cool Roofing Granules are 3M’s latest innovation in combating heat islands. They work by reflecting the light back off the surface of structures.

heatmap of cooling on roof

Roofs and pavement make up about 60 percent of urban surfaces in some U.S. cities.

When the sun is shining, this concentration of warmed surfaces can turn the heat up an extra 3 or 4 degrees, according to Berkeley Lab’s Heat Island Group.

One solution to reduce this urban heating? There could be one in your roof – reflecting the light back off the surface of structures.

Roofing granules

According to Frank Klink, 3M laboratory manager, the ability to reflect light can help reduce the amount of air conditioning you need – ultimately cutting back on local energy consumption and the need for fossil fuel. In states like California, where power grids are often stressed on hot afternoons, this reduction in energy consumption is crucial.

Solar energy reflectance – how it works

One of 3M’s contributions to reducing urban heating comes in the form of Cool Roofing Granules. The technology behind the new roofing granules was originally used on military hardware – like aircraft and armor – to make it less visible, says Frank.

3M’s product development team wanted to create a variety of colors that would preferentially reflect back more infrared radiation – which makes up a little more than half of the solar radiation that hits the earth. The colored coatings that go on the granules reflect more of the sunlight back up to the sky – so that less goes into heating the roof.

“Our focus was on developing a way to absorb less radiation but still offer a variety of colors to customers,” says Frank. “We realized that they needed to reflect more of the infrared portion. We needed granular structures that reflected back.”

Cool Roofing Granules are mostly sold in the U.S., because many other countries use metal, clay or asphalt. “There is a growing awareness outside the U.S.,” Frank explains, “that we may see a growing demand for these granules in the tropical areas of the world.”

Shingles differences asphalt and 3m granules.

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