SPF (Spray Polyurethane Foam) Roofing is an excellent option for restoring or maintaining an existing roof as well as for new construction. The combination of SPF and elastomeric roof coatings create a high performance, energy-efficient roofing system due to high solar reflectance and thermal emittance properties providing protection against UV and IR radiation, as well as, customizable levels of insulation to the roof. There are four common roof coatings that can be used over an SPF roof, they are: acrylic, silicone, butyl, and polyurethane.
Now you are probably wondering, ‘What SPF roof coating is the best?’ ‘Which one will give me the most benefits?’ ‘How do I know which one to choose?’ Let me explain.
Acrylic elastomeric coatings are the most popular and rated highest among the four choices because they have ability to adhere to most types of roof membranes and have a long history of success. Our acrylic coatings have high quality solids (pigments), resins, and fire retardants that work together to produce a seamless, durable, monolithic, flexible membrane with excellent aging values and resistance to UV damage. Our coatings have very low VOC’s, making them easier on the environment and the applicator. Acrylic coatings typically reflect 70% - 80%+ of the sun’s UV rays from the roof, providing the critical protection to the SPF and the roof substrate, while keeping the building cooler as less energy and heat was absorbed. AcryShield A590 is an excellent choice for both a base coat and a top coat when choosing a SPF roof coating because its’ ultra-high reflectance properties.
Silicone coatings are ideal because they offer a high degree of aging and water resistance, while providing great elongation; however, silicone coatings cure moderately soft compared to acrylic. This allows the silicone to attract dirt easier, creating a darker roof membrane with lower ability for reflectivity. The softer coating may provide less protection to the SPF roof membrane, making it more likely to have physical damage from foot-traffic during maintenance work on HVAC systems, roof maintenance or other work constructed on the roof-top. National Coatings has a Silicone Roof Coating with High Solids for those who prefer it to the acrylic coatings, the SRC 720.
Butyl coatings when cured create a very hard, strong surface making it an ideal coating for cold-storage centers because of its exceptional low water-vapor permeance. Butyl coatings have excellent blocking resistance, creating an easy to clean membrane, while providing foot-traffic protection; however, this hard finish has its’ disadvantages as it tends to become brittle as the coating ages. Butyl coatings are solvent-borne with high levels of harmful VOC’s, strong odors and are flammable. The other real disadvantage to butyl having excellent blocking resistance is that it cannot be re-coated in the future to avoid a costly tear-off since butyl will not stick to itself.
Polyurethane coatings work well as a SPF roof coating option but may be difficult to apply with the correct ratio of the two components for proper consistency. The two-components after they are mixed together, must also be used quickly as the product has a short shelf life of several hours.
For more information on roof coatings and their benefits, download our Considering Coatings? A Free Guide to Roof Coatings brochure.