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DOE Buildings to Get Cool Roofs that Reflect Heat Back into Space

Report Confirms Cool Roofs Can Offset Carbon Dioxide Emissions and Mitigate Global Warming

By Amy Westervelt

Jul 21, 2010

Cool roofs also have the benefit of being cheap and easy to implement; people can simply make the switch when it’s time for a new roof, or opt for white instead of black when they’re building. There is no cost difference. “Instead of having to convince 3 billion or so urban dwellers to change their individual spaces, you have to convince only the policy makers,” Rosenfeld said. “In the U.S. most states have standards for new buildings.”

In California, for example, Title 24 has stipulated since 2005 that all commercial buildings with flat roofs must have white roofs. The state also implemented a building code in 2008 that required residents of its four hottest zones to have “cool roofs,” which are not necessarily white, but painted colors that are less heat-trapping than black (red, blue, green). The decision was made to give residents more color options, according to Rosenfeld, because many US homes have sloping roofs and the color white is not always aesthetically pleasing on such homes.

In addition to white roofs on buildings and residences, Rosenfeld hopes to see more vehicles go for white tops in the near future. On a recent trip to India he spoke with policy makers about painting the country’s blue-roofed trains that have no air conditioning white on top. “I think I convinced them,” he said.

Rosenfeld said California is getting ready to mandate cooler colors for government fleet vehicles as well, to reduce the air conditioning load on vehicles. “Really all vehicles should have a white top and then whatever color you want underneath,” he said.

As unlikely as it might be to get all Americans to agree to that color scheme, it’s even tougher to get people to embrace the idea of “cool” pavement, according to Rosenfeld. Not because the public has some sort of affinity for black asphalt, but because they just don’t care one way or the other.

“It’s the tragedy of the commons,” Rosenfeld said. “Cool roofs are easy because you can sell people on the idea that they’ll be more comfortable in their buildings or homes and their electricity bills will be lower, but they don’t see any direct benefit from changes to the pavement so that’s going to take a longer time.”

White Roads?

White roofs work well in part because they do a good job reflecting light away from the surface. I'm not sure that this would be a desirable effect on roads were visibility in of great concern. We don't want drivers being blinded by a white road at the wrong angle.

winter heating

You have to remember in the winter months most days are overcast or if its snowing already have a white roof because of the snow.  So either they don't get much sun in the winter months or they get no sun because they are snow covered already.  Plus they are just saying largest 100 cities around the world.  I don't know this for a fact but I would guess that 90%+ are within the 45 degree longitude lines so probably don't get alot of really cold winters that would cause a larger need for heating then cooling in the winter. 


Also most likely, again I don't know this for a fact, but cooling is probably requires more energy than heating. 

Does this take into

Does this take into consideration climates where buildings are heated rather than require energy for cooling?  I mean it seems quite a reputable study, but any mention of heating homes seems distinctly missing.  It doesn't seem like it would be effective to be reflecting heat energy in the winter where buildings require heating.

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