Top 10 Green Roofing Options

Factory-applied or Field-applied Coating

This is a material that can be applied to virtually any type of existing roof -- even metal. It's either applied at the factory or on site. Generally, the products are bright white or contain reflective pigment. "Half of the solar energy coming in is the infrared light. That's energy we can't see," Clark says. "Those pigments can reflect the infrared."

The National Roof Coatings Institute reported that after the roofs on an entire city block in Philadelphia were coated with "highly reflective white coatings," the surrounding air temperature dropped by 1 degree in summer heat.