Every summer, millions of Americans turn on the air conditioning and brace themselves for the electric bill that comes with it. Most never think about the fact that the color of their roof might be working quietly against them. According to the Lawrence Berkeley National Laboratory overview of cool-roof research, a dark rooftop can absorb so much sunlight that its surface temperature is 50 to 90 degrees Fahrenheit hotter than the surrounding air.
A reflective “cool” roof, by contrast, stays only about 10 to 20 degrees warmer than the outside air. That gap is why one of the country’s premier energy research labs has spent decades studying rooftops as a simple fix to the summer energy problem.
