Cool Roofs

qualified roof coating material mitigate the amount of air conditioning needed in buildings, and can reduce energy bills by up to 50 percent. The Cool Roof Program defines certain standards for solar reflectance, three-year aged maintenance of reflectivity, and emission in roof coating systems. Reflectivity is the percentage of the sun’s heat a roof keeps off a building, and emissivity is the percentage of heat a roof lets out of a building.

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Lighter colored (white) roof coatings reflect the sun’s UV rays and heat and can lower the temperature of the roof by up to 100° degrees F.

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The most common cool roof coatings used over sprayed polyurethane foam (SPF) and other roof deck surfaces are light/white colored. The most common types are:

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• Acrylic – Acrylic coatings are typically water-based. They are a common staple in the market because they are cost-effective, environmentally friendly, and easy to use. They are typically high in reflectivity, which cools the roof down. Acrylic coatings can be elastomeric, allowing for fluctuations in temperature without affecting the actual coating. In general, acrylic coatings help reduce cooling costs at a more economical value, while at the same time increasing the service life a roof surface by protecting it from UV exposure.

• Silicone – Silicone coatings are also very common, and because of their permeability, they tend to be applied on spray polyurethane foam (SPF) roofs.  Silicones are also very well suited for areas with extreme temperature ranges and where UV exposure is more frequent. Once the base coat is applied, a slick surface is generated, and only another layer of silicone coating can be applied as the recoat.

• Urethanes – Polyurethane coatings provide a highly durable surface that protects the roofing system from a wide variety of conditions. Urethanes typically have higher tensile strength, allowing the coating to resist expansion and contraction of the roof system. This can be a crucial protective features in the high stress areas of the roof where buildings endure the most abuse, including wall flashings or around penetrations. Urethane coatings can derive from aliphatic or aromatic formulations. Aliphatic urethane coatings provide long-term protection from UV exposure while aromatic urethanes provide the core benefits of a urethane coating but may affect the integrity of the film over time since aromatic coatings can chalk due to UV exposure over time.

• Polyurea – Polyurea coatings are 100% solids materials formed by the reaction between an isocyanate, which can also be aromatic or aliphatic, and an amine resin. Polyurea coatings are easy to apply and they have a rapid-curing reaction that is not affected by moisture or temperature, unlike other coatings. Polyurea can smoothly adhere to virtually any roof substrate and bolster the roofline along the way.