Does a white roof really work?

Dear Dr. Green: I’ve read about white roofs and heard a lot about Philly’s Coolest Block Contest, but that was before the recent heat wave. Ninety degree temperature seems like too much for a measly coat of paint to handle. Does that stuff really work?

A: Skepticism is natural, but this isn’t snake oil we’re selling. A white roof really will save you money, make your home more comfortable, and help slow the rate of climate change.

Let’s first look at the science. During a heat wave, black asphalt roofs can reach 195 degrees Fahrenheit. Much of that accumulated heat radiates into the building, rendering it uncomfortable and, in some cases, dangerous. Air conditioning systems consume great amounts of energy as they fight to counteract the effects of the sweltering roofs.

Experts recommend acrylic, elastomeric white roof coating as an effective way of cooling homes.  Roofing materials with an EPA ENERGY STAR rated solar reflectance of more than 65 percent re-radiate much of the solar radiation back into the sky, reflecting heat much better than a traditional roof.

A healthy suspicion never hurt anyone, but ignoring the truth about white roofs can cost you. White roofs reduce air-conditioning bills by an average of 22 percent. White and reflective roof materials also extend the life of a roof by approximately 10 years, greatly reducing lifetime maintenance costs.

Still don’t believe it? Try this on for size: because so much less heat is absorbed, the benefits extend beyond your energy bill. White roofs essentially restore a piece of the polar ice caps: research shows that by increasing the earth’s reflectance (or albedo) and returning the sun’s heat to outer space, they help both you and the climate stay cool during a heat wave.

Without a doubt, houses with white roofs feel cooler and are more comfortable to live in. But don’t take our word for it—just ask people from the 1200 block of Wolf Street.

As winners of the Coolest Block Contest (CBC), all participating homes on the 1200 block of Wolf Street are receiving a free energy audit, air sealing, insulation, and white roof coating. The homes have yet to be fully retrofitted, but residents are already reporting that their homes are cooler on account of white roofs.

CBC winner Terry Jack perceived a change in her home almost instantly. “I have to say that there actually is a noticeable temperature difference on the second floor on the really hot days,” says Jack.

Cory Suter, founder and chief operator of BioNeighbors, the contractor responsible for installing the white roofs for the 1200 block of Wolf Street, has received very positive feedback. “There is a tremendous difference to the interior comfort of the house,” explains Suter. “People have been really impressed with how much cooler their upstairs is and how much less their air conditioner is running after installation.”

You must be kicking yourself that you don’t have a white roof. Luckily, the opportunity to get one hasn’t passed you by. It’s not too late to install a white roof! It can take as little as one day to install and you can start feeling the benefits almost instantly. So get comfortable and give yourself, your air conditioner, and your wallet a break.

Believe it or not, white roofs are super cool.

Our energy Q & A column from Philly's Energy Coordinating Agency has a special expert, Dr. Green, to answer your questions at

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