Specific Light or Reflective Exterior Finishes in Hot Climates

As a second line of defense against damage from solar radiation, light colored materials and finishes can be selected. White is excellent and aluminum reflective-type coatings are even better. Light colors can reduce summertime cooling load and should reduce energy bills—especially in cooling-dominated climates—by lowering the solar heat gain into the building.

If properly accounted for in cooling load calculations, lighter colored roofing may allow for the use of smaller capacity air conditioning units. For example, REM/Rate modeling software has a simple “Roof Properties” set of inputs including the color of the roof covering. Users of this software or similar programs can very quickly model and observe the changes which result to the cooling load from switching from dark to light or reflective roof coverings.

The effect of building exterior color on solar heat gain is illustrated in Figure 6–3. It is very important, however, to keep light colored finishes like roofs relatively clean to take full advantage of their reflectivity.

Similarly dark colored finishes can be chosen when more solar absorption is a wanted effect —especially in climates where heating is the dominant load.