Even in hot, sunny climates, it's common to see dark shingle roofs. That heat-absorbing choice carries a significant energy penalty: In sunny climates, heat gain through the roof makes up a major share of a house's cooling load.

People try different strategies to limit heat gain through the roof. Extra ceiling insulation, extra ventilation, under-roof radiant barriers, and sealed attics with insulated roof decks can all help in certain circumstances. But research shows that the single most effective way to cut the cooling loads from a hot-climate roof is to make the...

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