Elastomeric Roofing Materials

Keeping Roofs Cool

• You can theoretically cool any surface by painting it white. Light colors increase albedo, or ability to reflect the sun. If a roof can reflect solar energy back into the atmosphere -- or block it, as white paints do -- the surface doesn’t absorb that heat and naturally stays cooler. Houses and other buildings with white roofs stay cooler, conserving energy. But paint doesn’t adhere well to every surface, and many paints don’t stand up well to the sun’s intensity.

Elastomeric Roof Coatings

• Elastomeric paints were developed to expand the range and increase the durability of white and light-colored roof coatings. The elastomer is the binder, or the substance that combines color pigments, water and other ingredients. In most elastomeric paints, this substance is acrylic, a water-based plastic. Zinc oxide and titanium oxide are common additives. These pigments make the coatings bright white and highly reflective.

Ceramic Coating Additives

• Some manufacturers add ceramic beads to their elastomeric roof paints, a practice said to increase the coating’s insulation value and the building’s energy efficiency. But according to Tom Silva of “This Old House,” extensive performance testing suggests that the effectiveness of these “ceramic paints” is the same as standard elastomeric coatings.

Using Elastomeric Coatings

• These flexible, reflective coatings can be applied to almost any roofing membrane and are often applied after polyurethane, which provides a waterproof layer. They are frequently used on single-ply rubber and modified bitumen roof surfaces and can also be used on some types of asphalt. They also work on metal roofs. Compatibility between the coating and roof is essential for adherence. Apply elastomeric coatings with a brush, roller or sprayer.

Maintaining Elastomeric Coatings

• Many but not all elastomeric coatings are waterproof. Even waterproof coatings may not stand up well to intense weather, so protective topcoats are often applied. Dust can change the appearance of a coated roof but doesn’t greatly affect its performance. Acrylic elastomeric surfaces aren’t cleanable in the usual sense. They cure from the outside in, and “chalk up” with wear, exposing whiter, fresher lower surfaces. Applying a new topcoat periodically is cheaper than reapplying the coating. Reapply elastomeric coatings every three to seven years.