LA Cool Extends To Home Rooftops

Air conditioning can suck up massive amounts of energy on hot summer days in California, driving demand for power that despite the state’s renewable energy gains, often comes from fossil fuels. But Los Angeles hopes to take a little bite out of that demand with a new requirement that all new and refurbished home roofs take advantage of cool roof technology.

The group Climate Resolve, which has been pushing for the update to the municipal building code, said the recent move by the city council made L.A. the first “major city” to take such a step.

“Cool roofs are a win-win-win for the people of Los Angeles,” Jonathan Parfrey, executive director of the group, said in a statement. “Keeping temperatures down on extreme heat days will protect lives; energy efficiency will save millions of dollars; and cool roofs will help Los Angeles combat global climate change at the local level.”

According to the U.S. Department of Energy, the temperature on a dark roof that absorbs much of the sunlight that shines on it can approach a sizzling 180 F on a hot day. But cool roofs can trim the roof temperature by up to 50 degrees, thus cutting the amount of heating migrating into the building.

That’s one reason that in 2010, then-Energy Secretary Steven Chu ordered that any new or refurbished department building roofs be done cool-roof style. Another reason is that in addition to cooling buildings, cool roofs can help keep whole cities cooler. Accordign to government scientists, “Cool roofs lower urban air temperatures by reducing the amount of heat transferred from roofs to the air, mitigating the urban heat island effect.”

The good news, too, is that the DOE says cool roofs usually don’t cost any more than standard roofs, and that’s almost certain to be the case in L.A., where the Los Angeles Department of Water and Power offers rebates worth between 20 and 30 cents per square foot on cool-roof installations.

And if a bright white roof sounds like it would create a lot of glare, the LADWP notes – as we’ve reported in depth – that “eligible cool roofs now actually come in many colors, including tan, grey, and terra cotta.”

Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.