White Roofs Cool Local & Global Warming
Some things are easy. A new study from researchers at NASA and New York’s Columbia University has concluded that painting a city’s roofs white or another light color could reduce the local ambient temperature by 5 percent or more during hot summer months. This negates the phenomenon scientists refer to as the “urban heat island effect”, in which the dark jungles of asphalt, metal and concrete turn cities into heat reservoirs, soaking up the warmth of the sun instead of reflecting solar radiation back into the atmosphere.
In New York City, it was discovered that a white-surfaced roof was 43 percent cooler than its black counterpart. The city passed a law in 2007 to reduce its greenhouse emissions by 30 percent by 2030; increasing the city’s albedo (the amount of reflected solar radiation) by brightening its surfaces is one of the quickest, cheapest and most effective ways to achieve significant reductions.
After announcing a plan to alter roofs atop the U.S. Department of Energy and other federal buildings in the summer of 2010, Energy Secretary Steven Chu said, “Cool roofs are one of the quickest and lowest-cost ways we can reduce our global carbon emissions and begin the hard work of slowing climate change.”