Spray foam insulation and elastomeric roof coatings combine to lower energy costs:
- High R-value (depending on Manufacturer R-value of R6-6.5)
- Most roof coatings are light colored which helps reduce internal building heat
- Reduces or eliminates thermal bridging
- Reduces adding to the landfill as there is little tear off and replacement
Spray foam insulation requires protection from the sun’s ultraviolet radiation and the elements. Elastomeric spray roof coatings protect and seals the spray foam insulation from the elements. Once a spray foam roof is applied, elastomeric roof coating is applied creating a protective layer. This protective layer produces a durable weather resistant surface which can be walked on for routine maintenance of the other components typically located on a roof such as HVAC.
Below are the most common elastomeric roof coatings used over spray foam insulation:
- Acrylic Silicone
- Crushed Rock
Yes, crushed rock spread over the spray foam insulation is a successful system; however, elastomeric roof coatings are more common. Elastomeric roof coatings are spray applied as a single component; or in some cases, as a plural component. The above list of elastomeric roof coatings all have different physical properties and vary in cost. Roof coatings are usually installed as a base coat followed by a top coat. Granules can be embedded into the final coat which adds an added protection against UV light, light roof traffic, birds, and hail resistance. In time, these coatings will require maintenance or re-coating. Once these elastomeric roof coatings are recoated, the warranty can be renewed as well. The average duration between re-coats is fifteen to twenty years.
A spray foam roof, like most other systems, will expand and contract during different climate conditions. It is very important that the protective elastomeric roof coating can expand with the spray foam insulation, or damage will occur in the form of cracks or delamination. Physical characteristics; of elastomeric roof coatings such as elongation and tensile strength are something Tillotson takes great consideration in when picking the right elastomeric roof coating.
The Use of Roof Coatings In The Midwest
Pros: With high humidity in the Midwest, and the chemistry of Silicone, Silicone is able to cure quickly after the coating is applied. If it were to rain shortly after the roof was coating, silicone would not wash off where an acrylic roof coating would. Silicone roof coatings also can be applied at/or below freezing, which cannot be done with some other roof coatings. Silicone roof coatings have a high wear resistance, which means that in ten years, little to no wear is found.
Cons: Hail in the Midwest is a concern and can easily harm a silicone roof. Because of the chemistry of Silicones they usually have low tensile strength. The more tensile strength a coating has the more hail resistant the coating is. If the silicone is punctured, the roof will need to be re-coated with more silicone because silicone only sticks to silicone. Depending on the silicone not all silicones stick to each other.
Pros: Urethane coatings are among the tough coatings against hail due to urethanes high tensile strength properties. They can be applied in cold temperatures which gives longer application windows. Urethane roof coatings come in chemical cure or moisture cure. Chemical cure urethanes cure by mixing two chemicals and you have what is called a pop life to apply the coating before they cure. Moisture cure urethanes take in the moisture from the air and use that humid to cure.
Cons: Urethane coatings tend to have a higher cost. Some of these coatings put off an odor that can linger in the application area and some people find the order unpleasant. Applications of urethane coatings in and around air intakes has to be taken into account to manage the orders from urethane coatings.
Pros: These coatings are some of the strongest coatings on the market. Along with strength, they have a very low wear rate. Polyurea roof coatings are chemical resistant and corrosion resistant.
Cons: If the surface is not prepared correctly, the coating is more likely to detach from the substrate. A true white colored polyurea is hard to form, and the coating tends to yellow over time. Most of Polyurea coating has to be applied with a special sprayer call a plural component machine which drives up the price of application. Plural component just means the machine pumps two chemicals under pressure to a gun where the two chemicals are then mixed.
Pros: Acrylic is the middle of the road coating and is the coating of choice for Midwest contractors. Acrylic roof coatings are less expensive and easier to apply than others. If the coating is applied thick enough (30 mils), it can handle most hail up to golf ball size.
Cons: Since acrylic coatings are water-based, they can wash off, if not dry, before rain. Acrylic roof coatings can take hours to dry in low heat, low wind or high humidity. Cheaper acrylic coatings don’t last as long as other coatings and can become brittle and delaminate, especially in a bad hailstorm.