The sun's energy inevitably finds its way into the buildings on which it falls. In the summertime, this unwanted heat energy makes buildings hot and requires more air conditioning. Since the summertime sun rises high in the sky, the sun's radiant energy falls mainly on the roof, with east and west walls of buildings also receiving a significant share.

 

One of the simplest ways to keep solar heat out of buildings is to use reflective roofing materials. Then, the sun's radiant energy is simply reflected back toward the sky from which it came. In fact, reflective materials also help keep the building's environment (i.e., the city) cool, by reflecting solar energy back out into space, thereby reducing the heat island effect. The Cool Roofing Materials Database provides information about the reflective properties of different roofing materials.

 

Look for ENERGY STAR labeled roofing products, they reflect heat and can reduce peak cooling demand by 10% to 15%.

 

Another way to lower cooling costs and extend roof life is to put a light colored coating (also called cool-coating system) over an existing roof. Adding a cool coating is most beneficial for a building that meets these criteria:

 

Is in a climate with hot, sunny weather during at least part of the year

Uses significant cooling energy and/or has problems maintaining comfort

Has a large roof area compared to the rest of the building's surface area

Has roofing which tends to crack and age prematurely from sun damage