Los Angeles, the second most populous city in the U.S., has made history by becoming the first major city to require all new and refurbished homes have a “cool roof.” On December 17, 2013 the Los Angeles City Council unanimously passed an update to its Municipal Building Code. A cool roof is one that “reflects and emits the sun’s heat back to the sky instead of transferring it to the building below,” according to the Cool Roof Rating Council.