People who live in hot climates without air conditioning, like Greece or India, know that the key to keeping cool is to paint the roof — or, indeed, the whole building — a light color.
Turns out it could help counter global warming too. In London last month, Obama’s Secretary of Energy said painting roofs and roads light colors in urban areas could offset the impact of all the cars in the world for 11 years!
That comes on the heels of a report by a Lawrence Berkeley Laboratory physicist last fall that said that if the 100 biggest cities in the world installed white roofs and changed their pavements to be more reflective, it would offset 44 metric gigatons of greenhouse gases — or more than all the countries in the world emit in a year.
The science is simple: Light colored surfaces reflect light back into space. Dark surfaces absorb heat. Not only does that turn your home into a swelter box, forcing you to use more energy for things like air conditioning. It also traps more heat here on Earth and contributes to global warming.
Want to move in this direction? Here are a few things to know:
If you want to go white, you can use either paints or adhesive membranes. There are a slew of products to choose from. Your local hardware store or roofing contractor should be able to help you decide.
Remember to periodically scrub the roof clean. Grime and mildew can reduce a white roof’s reflective powers.
If you’re not crazy about going white, there are many other “cool roof” options, like aluminum roofs and zinc-galvanized sheeting. As long as the material you use has a high “radiative property value” — ie: the amount of solar energy it reflects — you’re good to go.
Check with your local utility company and municipal authority for any incentives or rebates which could reduce your costs.
Also check your local bylaws to make sure white roofs aren’t explicitly forbidden, as they are in some areas.