Cool Roofs are Green Roofs: Five Things to Remember when Considering a Cool Roof

Traditional asphalt shingle roofs absorb a large amount of radiant energy from the sun often creating what are called “heat islands”.  The heat island caused by the roof causes the temperature of the surrounding air to rise as well.  Indeed, according to a 2000 study by the Lawrence Berkeley National Laboratory, the surface temperature of a typical black asphalt roof can be as high as 170 °F in the summer in a warm sunny climate, even if the outdoor air temperature is only around 90 °F.  This heat island effect causes the building’s HVAC system to have to work harder to maintain a comfortable interior temperature of 70 °F, because the temperature difference between the roof and the inside thermostat is 100 °F.
Some of the incremental strain on HVAC systems can be alleviated through the use of a “cool roof”, which as it reads, works to reduce the temperature of a building’s roof.  The Lawrence Berkley National Laboratory Heat Island Group has monitored buildings in Sacramento with lightly colored, more reflective roofs. They found that these buildings used up to 40% less energy for cooling than buildings with darker roofs.

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