Cool roof coatings are best applied to low-sloped roofs in good condition [source: Environmental Protection Agency]. They are divided into two categories: cementitious coatings, which contain concrete or ceramic particles, and elastomeric coatings, which contain added polymers that make them less brittle and more adhesive to building surfaces.
Both cementitious and elastomeric coatings improve the solar reflectance of the roof surface. The primary difference is that elastomeric coatings act as a watertight membrane, while cementitious coatings must be applied over roofing materials that have already been thoroughly waterproofed [source: Environmental Protection Agency].
Cool roof coatings are sprayed, rolled, or brushed onto an existing flat or low-sloping rooftop to create a bright white, paint-like reflective surface These coatings are more commonly used in re-roofing projects than in new construction, and their cost ranges from about 75 cents to $1.50 per square foot [source: Pacific Gas and Electric].