The temperature of shingles on top of an average suburban house can reach 160-170 degrees F on a hot July afternoon in Florida. It's not the air outside, not the attic underneath; the actual roof surface of the house becomes so hot that you'd think twice before touching it. In 1991, researchers coated the green-gray shingle roof of a home in Merritt Island, Florida, with a reflective material to observe what would happen. The surface temperature was lowered to approximately 110 degrees.
A 1995 Florida Solar Energy Center study titled “Measured Cooling Energy Savings from Reflective Roofing Systems in Florida: Field and Laboratory Research Results,” showed that the roof reflectivity of a single-story home on Merritt Island that was coated with a reflective material increased from 0.22 to 0.73, while the temperature of the shingles fell from approximately 160-170°F before treatment to about 110°F after the coating was applied. The report also found a 10.5% reduction in air-conditioning energy use at the Merritt Island test home. More than three decades later, the underlying finding remains relevant: roof reflectivity can affect how much heat a building absorbs and how much energy is needed for cooling.
Why roof color affects cooling costs
When it comes to roof color, the younger generations may not be much concerned about it. However, the physics doesn't bend: When solar rays strike a dark roof, it absorbs almost all of them, and heat has to be removed from it somewhere. Some of it spills into the attic, some of it intrudes into the living area underneath, and all of it will eventually be an issue with your air conditioning system, consequently, an issue with your monthly bill.
