Transitioning to Cool Roofs
In the effort to slow the pace of global warming, researchers and policy makers are encouraging the use of lighter colors for rooftops and streets worldwide. Dark, non-reflective surfaces which are common for asphalt and asphalt shingles, absorb heat from the sun and create a "heat-island" effect, plus a greater need for air conditioning. Lighter surfaces would reflect the sun’s rays back to outer space, reducing ground-surface temperatures and overall energy requirements.
This is an effort that has been promoted aggressively by the US Department of Energy (DOE) Secretary, Steven Chu. Talking with Jon Stewart on the "Daily Show", Chu said "when you're thinking of putting on a new roof, make it white. It costs no more to make it white than to make it black." In fact, Chu has instructed all DOE offices to install "cool roofs" on new department buildings or when replacing old ones.
"Cool roofs are one of the quickest and lowest-cost ways we can reduce our global carbon emissions," he said in a DOE statement. It is one of the easiest ways to fight global warming. All it involves is choosing a lighter color when installing a new roof.
The same concept can go with all urban surfaces. Researchers at the Lawrence Berkeley National Laboratory (LBNL) determined that for cities with populations over one million, increasing surface reflectivity would be equivalent of offsetting the heating effect of 1.2 gigatons of carbon dioxide emissions per year. It is also equivalent to removing 300 million cars off the road for twenty years.
Roofs and paved surfaces cover 50 to 65 percent of the planet's urban areas, where more than half the world’s population lives. There are experts that predict that with population increase and migration to the cities, almost three quarters of the world will live in urban areas. This means more buildings, more roofs, and more roads.
It is also important to transition to lighter color roofs and surfaces because it makes economic sense. Air conditioning is one of the largest energy consumers during the hot summer months, and the main reason why electricity bills sky rocket. Darker roofs absorb solar heat into the house, while lighter roofs reflect it away. The LBNL researchers found that outfitting eighty percent of air-conditioned buildings in the US with white roofs could save $735 million per year by reducing utility bills.
There is no reason why light colored roofs shouldn't be adopted on a large scale. Sure a white roof may look funny on your house compared to your gray or black roof, but it doesn't cost any more. The question isn't, why do it. The question is, why have we not done it already.