White Roofs

Can light-colored rooftops and roads really curb carbon emissions and combat global climate change? The idea has been around for years, but now, a new study by researchers at Lawrence Berkeley National Laboratory that is the first to use a global model to study the question has found that implementing cool roofs and cool pavements in cities around the world can not only help cities stay cooler, they can also cool the world, with the potential of cancelling the heating effect of up to two years of worldwide carbon dioxide emissions.       

Because white roofs reflect far more of the sun’s heat than black ones, buildings with white roofs will stay cooler. If the building is air conditioned, less air conditioning will be required, thus saving energy. Even if there is no air conditioning, the heat absorbed by a black roof both heats the space below, making the space less comfortable, and is also carried into the city air by wind raising the ambient temperature in what is known as the urban heat island effect. Additionally, there’s a third, less familiar way in which a black roof heats the world: it radiates energy directly into the atmosphere, which is then absorbed by the nearest clouds and ends up trapped by the greenhouse effect, contributing to global warming.