If you walk into the city on a sunny, summer day and feel like it is warmer than the suburban home you left earlier, it isn’t your imagination. The “Heat Island Effect” is a term that refers to a localized rise in ambient, outdoor temperature due to dark materials absorbing light from the sun. While asphalt roads contribute meaningfully, roofscapes are the most abundant culprit with a large number of existing flat roofs in this county being black—either tar, asphalt or a rubberized membrane. In full summer sun, a black roof can reach temperatures of 170 degrees. When the number of these roofs located in close proximity rises so does the amount of heat captured and radiated back into the air.
Though it is occurring at some scale on any dark-colored, man-made surface, the effects are most strongly felt in urban conditions where streets and the tops of buildings make up most of the net surface area facing the sky. In a city like New York, the result can be a local air temperature 5 to 10 degrees higher than surrounding townships in the depths of summer. Keep in mind, Manhattan is also on the coast which means that this temperature rise is happening despite the cooler normally found from coastal winds. Continue Reading…