Cool Roofs

Cool roofs are the roofs that can deliver high solar reflectance (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to the building) and high thermal emittance (the ability to radiate absorbed, or non-reflected solar energy).[1] The benefits associated with cool roofs include reduced cooling energy load, reduced air pollution and greenhouse gas emission, and improved human health and comfort. Cool roofs may extend the roof service life and help mitigating the urban heat island effect.[2] Cool roofs achieve cooling energy savings in hot summers but can increase heating energy load during cold winters.[3] Therefore, the net energy saving of cool roofs varies depending on climate. However, a 2010 energy efficiency study [4] looking at this issue for air conditioned commercial buildings across the USA found that the summer cooling savings typically outweigh the winter heating penalty even in cold climates near the Canadian border giving savings in both electricity and emissions. Without a proper maintenance program to keep the material clean, the energy savings of cool roofs can diminish over time due to albedo degradation and soiling.[5]
While it is true that cool roofs are mostly associated with white roofs, they come in a variety of colors and materials and are available for both commercial and residential buildings. Note that today's "cool roof" pigments allow metal roofing products to be EnergyStar rated in dark colors, even black. They aren't as reflective as whites or light colors, but can still save energy over other paints.