White Trumps Black in Urban Cool Contest
A comparison of the surface temperatures of a white roof at MoMa P.S. 1 in Queens with those of a black roof last June to August. The roof was coated with a white acrylic paint. One hundred seventy degrees Fahrenheit is the approximate temperature to which chicken should be cooked. It’s also the temperature that was recorded on some asphalt roofs in New York City last July during a heat wave that set a record for electricity use.
Because they absorb sunlight, dark roofs, dark buildings and dark streets and sidewalks make cities especially sweaty, a phenomenon known as the urban heat island effect. New York City can often be up to 5 degrees hotter than surrounding areas. So one of the simplest ways to cool cities, lower electricity usage and reduce the city’s carbon footprint is to make rooftops white, ensuring that they reflect heat rather than absorb it.
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