Environmental solutions are rarely black-and-white. But making roofs more reflective—basically, painting them white—may be a simple strategy for curbing climate change, experts say.
Dark roofs reflect about 10 to 20 percent of sunlight, whereas so-called cool roofs send about 70 to 80 percent of it back into the atmosphere, according to researchers at Lawrence Berkeley National Laboratory in California.
A reflective-roofed house or building with 1,000 square feet (93 square meters) of roof area would offset 10 tons of carbon dioxide emissions, a greenhouse gas that contributes to climate change, according to a 2008 study led by Lawrence lab scientists in the journal Climatic Change.
And it’s also an energy-saving boon: White roofs cut on air-conditioning use by 20 percent, thereby reducing greenhouse gas emissions from power plants.
Not to mention cooler roofs also cool down urban dwellers—which now make up half the world’s population—during summer months.
That’s because reflective roofs and pavements reduce sweltering city temperatures—a city can be up to 5.4 degrees Fahrenheit (3 degrees Celsius) hotter than surrounding areas, according to the U.S. Environmental Protection Agency.
Such high temperatures require that buildings crank up the air conditioning and overall increase their energy usage, which in turn emits more pollution and degrades air quality.
Put together, the combined effect of energy and air-quality savings from increasing reflective surfaces just in the United States may exceed $2 billion a year, according to Lawrence scientists.
White roofs as a win-win hasn’t been lost on U.S. Energy Secretary Steven Chu, who has been advocating for the roofs as a simple and cheap form of geoengineering, or manipulating environments to combat global warming.
“Now you smile, but if you look at all the buildings and make all the roofs white, and if you make the pavement a more concrete type of color than a black type of color, and you do this uniformly … it’s the equivalent of reducing the carbon emissions due to all the cars in the world by 11 years,” Chu told the U.K.’s Independent newspaper in May.
To spread the white-roof gospel, the Lawrence lab researchers suggest launching an international campaign in large temperate and tropical cities to install white roofs and pavements when such structures are built or repaired.
An international cool-cities program need not require “delicate negotiations,” the authors point out, and could be a global, coordinated step in combating global warming.
In the meantime, if you’re keen on cooling your own roof, check out the Energy Star program’s Web site, which offers a useful guide for reflective-roof products already on the market.
Likewise, you can find comprehensive information on so-called cool roofs at the U.S. Deparment of Energy’s Web site.
Go raise the (white) roof!
–Learn how to get a green roof on a shoestring budget.
–Browse Green Guide’s Home Improvement hub for more ecofriendly housing ideas.
–Check out green roof photos at National Geographic magazine.
Photograph courtesy U.S. Department of Energy