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May 28, 2009 10:59 pm US/Central
Good Question: Do White Roofs Save Energy?
(WCCO)
For every gallon of gas we burn, we pump about 20 pounds of carbon dioxide into the air. Over time, that's a lot of greenhouse gas.
So you can understand why taking every car off the road for more than 10 years might help slow the threat of climate change.
America's Energy Secretary said we could get the same effect by painting our roofs white. Sound ridiculous? Maybe, maybe not. Does the planet just need a fresh coat of paint?
It is an unlikely laboratory, but for Tim Leonard and ER Systems in Rockford, Minn., a large, flat rooftop they use for testing is the key to saving money and possibly saving the earth.
"We think of the roof as low-hanging fruit. It's something easy to modify and you get a big benefit out of it," said Leonard. "There are billions of square feet of black roofs across the country."
Those roofs are bouncing heat into the air and making air conditioners work harder. So ER Systems makes stuff to make roofs white. It's like paint, but fancier and a lot thicker.
It's easy to tell a chunk of black roadway is hot just by standing on it, even on a 75-degree day.
Leonard compared 140 degrees on a black roof with 97 degrees on a white roof. So why are so many roofs a dark color?
"It's just really been the way we've always done it," said Senior Vice President of LHB Architects Rick Carter
At LHB Architects, every commercial building they design has a white roof.
"When you do the math on carbon emissions, buildings are much a bigger contributor than cars," said Carter. "In Minnesota, the contribution to global warming is at least 50 percent buildings. Cars will always be less of an issue, they're just the one that seems most obvious to people."
That's why some road projects are going with concrete, to reduce the urban heat island issue. In California, it's the law, making all flat roofs light-colored. Soon the same will apply to sloped roofs, like the ones on our homes.
So does it make sense to put white roofs on our homes? It's not as important as making flat roofs white, because sloped roofs don't absorb as much heat.
Here in Minnesota our roofs are white for several months anyway from snow, so there's not as much benefit to changing them.
(© MMIX, CBS Broadcasting Inc. All Rights Reserved.)
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