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Using paint to cut your energy bill

Construction crews laying down a reflective roof in Washington DC.
Construction crews laying down a reflective roof in Washington DC.
From the American Geophysical Union, photo by Maria-José Viñas.

Sometimes, solar energy can work against us. If you’ve ever had the air conditioning cut out in July, you know exactly how badly. LA uses a lot of energy during the summer in trying to keep cool. More efficient air conditioners, renewable energy to run them, better insulation, that’s all great, but there’s something far simpler that can be done right now to cut down on cooling costs: Paint roofs white.

In an odd study for a winter month, the National Center of Atmospheric Research (NCAR) has made a computer model that shows how cities can be cooled down by painting roofs white. Cities tend to be hotter than less developed areas in the summer because they have more dark surfaces in them (asphalt roads, tar roofs, etc.) to absorb the sun’s warmth. White roofs would reflect some of that heat back into space.

The NCAR’s program estimates that painting the roofs in New York City white could cool reduce summer temperatures in that city by as much as 2 degrees. White roofs would also mean that the buildings underneath them would be able to use less energy to keep cool in the summer.

The New York Times quoted a study that showed a home with a reflective roof could use 20% less energy in the summer.  Wal-mart has embraced the idea, using white roofs on 75% of their US stores, and many sunny cities around the world are encouraging the use of reflective roofs to cut down on energy consumption.

True, a white roof can make for a chillier winter. A white-roofed building in a cold climate might end up using all the energy it saved in summer to warm back up in winter. But with a winter as mild as ours usually is, it might be worth looking into getting some reflective roof tile-- or just crawling up a ladder with a roller and a few cans of glossy white.