White Roofs are recognized energy savers

There are many advantages to changing a black, flat roof to a lighter, white surface.  Lighter colors reflect light, which lowers the amount of heat absorbed and therefore decreases the need for air cooling inside the building. This reduces utility bills in a dramatically easy and cost effective manner. Estimates of a 10% energy reduction are achieved from something as simple as painting the tar. 

Several states (California, Georgia, Florida) prescibe or encourage flat roof installations to be white. ASHRAE (American Society of Heating, Refrigerating, ashrae.org/and Air Conditioning Engineers)  is crediting white roofs in the latest version.

In cities, with many paved surfaces, there is a "heat island" effect, making the city hotter than the rural areas.  White roofs may reduce the heat island effect.