New Research Shows Californian Roofs Creating Heat Island, Exacerbating Already High Temperatures


roofResearchers have created a new tool that lets Californians see whether or not their roofs are contributing to the “heat island effect,” which exacerbates the problem of extremely hot temperatures.

The research team surveyed the rooftops of five major cities in the Golden State to get a better sense of just how much heat buildings reflect or absorb. The darker the roof, the more heat it tends to absorb, which warms not only the building it covered, but also other buildings around it. Lighter colored roofs, on the other hand, reflect heat energy back into the atmosphere, which helps the buildings stay cooler and save energy.

“If you conduct less heat into the building your air conditioner doesn’t have to work as hard to keep the interior of the building cool,” explained the study’s leader, Ronnen Levinson of the Lawrence Berkeley National Laboratory’s Heat Island Group.

After surveying the roofs of Los Angeles, Long Beach, San Francisco, San Jose, and Bakersfield, the researchers found that most of the roofs could be reflecting more light, and actually caused the cities’ temperatures to increase.

Los Angeles’ roofs were the darkest, and absorbed about 83% of the solar energy coming down on any given day. San Francisco and Bakersfield weren’t far behind, absorbing a whopping 82% and 80% respectively.

Luckily, Levinson said that something can be done about it. Flatter roofs can be retrofitted to reflect more light with a white coating, which can be easily applied. Sloped roofs and concrete tiled roofs can also be coated, too, but aren’t as easy to coat as flat roofs.

“As we work in Canada we actually recommend that homeowners go with darker shingles for their roofing, for the same reason they are recommending lighter roofing in California,” says  Dmytriy Rykov, Owner of DVR Roofing in Toronto, ON “When you have cold weather for the better part of the year, it is actually more energy conservant up here to get a little extra heat in the house from your roof absorbing the heat energy given by the sun.”

Asphalt roofs, which make up about 80% of residential roofs, aren’t as easily changed, though. However, Levinson suggests replacing asphalt shingles once they get worn out.

Considering the fact that L.A. is suffering from record-breaking temperatures, with many other parts of southern California facing similar difficulties, making such improvements might soon become necessary.

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