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
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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 expand with the spray foam insulation, or damage will occur in the form of cracks or delaminatation. Physical characteristics; of elastomeric roof coatings such as elongation and tensile strength are something we take in great consideration when picking the right elastomeric roof coating.
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The use of roof coatings in the Midwest
Pros: These roof coatings are often used along the coast where the humidity is high and hail is of little concern. Silicone roof coatings need water to cure, thus the high humidity helps them set faster. If it were to rain shortly after coating, silicone would quickly cure, where other coatings would wash off. 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, these coatings usually have low tensile strength and are not very hail resistant. If silicone is punctured, the roof will need to be re-coated with more silicone. Some silicone will not stick very well to a new coat, unless treated with a special cleaner.
Pros: Urethane coatings are tough against hail due to a high tensile strength. They can be applied in cold temperatures and, therefore, give longer application windows. These roof coatings come in chemical or moisture cure, so humid environments don’t make it hard to apply.
Cons: Urethane coatings tend to have a higher cost. Some of these coatings put off an odor that can linger in the application area.
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: A specific plural component machine is needed to create polyurea coatings. If the surface is not prepared correctly, the coating is more likely to delaminate from the substrate. A true white colored polyurea is hard to form, and the coating tends to yellow over time.
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. Acrylic roof coatings, if applied thick enough, can handle most hail in the golf ball size range.
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 hail storm.
Tillotson Enterprises, Inc.
715 Huron Drive
Kearney, NE 68847