Cool white roofs not only save cooling costs in the summer, but they help offset carbon dioxide emissions. White roofs and light colored pavements reflect sunlight directly back into space. Dark surfaces reflect less and radiate heat which gets trapped in the atmosphere by the greenhouse effect. Listen to what Energy Secretary Steven Chu has to say about the benefits of cool roofs and light-colored pavements.
According to Dr. Art Rosenfeld and colleagues at Lawrence Berkeley National Laboratory, the offset in carbon emissions from replacing the world's roofs and pavements with reflective white and light-colored surfaces is "roughly equivalent to taking the world's approximately billion cars off the road for 11 years."
Cool white roofs work best in hot sunny climates and may not be a good choice for colder climates. To determine whether your home or building might benefit from a cool roof, you can estimate potential cost and energy savings by using the DOE Cool Roof Calculator or this Roof Savings Calculator developed by Oak Ridge National Laboratory and Lawrence Berkeley National Laboratory.