Cool Roof

These new roofs shelter from the sun's heat and cut down on global warming.

Global warming and ozone worries are nothing new to most of us. Every day, alarming admonitions on the news warn us against the evils of thoughtless energy consumption, pollution and wasteful use of resources. So we recycle what we can, buy unbleached paper products and fit our cars with the latest earth-friendly technology. But who knew the color of your roof could be depleting the ozone layer?

Jeff Luvall, senior research scientist at NASA, has researched the effect sunlight has on the temperatures of dark surfaces like roofs. Luvall found that on a normal sunny day, the temperature of a light-colored shady sidewalk was 70 degrees. Inches away on a slightly darker though sunny patch of grass, the temperature was an uncomfortable 90 degrees.

You may be thinking that it doesn't take a scientist from NASA to know it's hotter in the sun than in the shade. But it's Luvall's next measurements that will shock you: the dark asphalt street next to that grassy patch was a scorching 123 degrees--that's nearly 20 degrees above the temperature that causes the human body to suffer heat stroke.

Now for the good news: the white stripes painted on that street were 10 degrees cooler than the surrounding dark asphalt. Ten degrees may not seem like a lot when you're talking about temperatures already above 100, but in your house, 10 degrees can mean the difference between being comfortable and being hot, between having to turn on the air conditioning and not. Naturally, houses sheltered by a dark roof are going to be hotter and require more energy to cool them.

Cooling our homes uses one-sixth of the total electrical power produced in the U.S., at a cost of $40 billion every year. To fulfill this increased demand for power, power plants burn more already-scarce fossil fuels, which results in increased air pollution, also known as smog. Making a bad situation worse, concentrated areas of dark roofs and asphalt roads emit heat into the air around them. Coupled with fewer green spaces and trees to create shade, this causes urban areas to be hotter than less populated areas, creating a phenomenon known as "urban heat islands." On summer days, these heat islands can be 6to 8 degrees hotter than the surrounding areas. Smog is also sensitive to temperature, and on hotter days, the concentration of smog is greater.

So as our dark roofs collect and emit heat, the air around them in our neighborhoods gets warmer, and the air pollution we cause by trying to keep cool gets worse. It's an ominous cycle, but fortunately the solution is as simple as the problem and has the same domino affect. Dan Varvais of the National Coatings Corporation says that his company's light-colored roofs repel the sun's heat rather than absorb it, making our homes cooler and requiring less energy used to keep them comfortable.

This cool roofing technology begins with a base of light, reflective materials, which are coated with polyurethane foam. An acrylic coating containing UV-blocking pigments is then sprayed on top of the foam. Much like people wearing sunscreen and thin layers of light-colored clothing, these light-colored roofs will act as a big reflector, providing protection from the sun's light and energy. As a result, our homes will absorb less solar heat, and that means fewer cooling costs.

With these reflective roofs in place, even northern cities like New York, Baltimore and Chicago could save $10 million to $15 million every year in cooling costs. The savings are closer to $40 million a year in sunny cities like Houston, Los Angeles and Phoenix. In all, Americans could save as much as $750 million a year, but the savings aren't just monetary. Lower temperatures both inside and outside our homes would result in less air pollution and ozone damage. "If we can lower urban air temperatures , we can improve the air quality, we can reduce energy consumption, we can reduce dependency on fossil fuels," Varvais says.

These high-tech roofs cut down on landfill waste, too. They last longer than conventional roofs, and since the installation is much like the application of paint, it's just sprayed directly onto the existing roof. This cover-over installation process eliminates the need for tearing out and disposing old roofing materials, which helped comprise the 11 million tons of asphalt waste already sitting in U.S. landfills.

Here's more good news: builders and engineers have begun experimenting with lighter-colored asphalt on our country's roadways, and some larger cities like Chicago, Salt Lake City and Sacramento already have regulations in place to begin combating the affects of these urban heat islands. Homes in these cities and in parts of Florida were outfitted with reflective roofs and were found to use as much as 40 percent less energy than homes in the same area with dark roofs.

The environmental and economical savings to be had with cool-roof technology are astounding. And according to Luvall, planting more trees in conjunction with this cool-roof technology can lower an average city's daily temperature by several degrees and accomplish the same air quality goals as the more daunting task of converting all of that same city's cars to electric power