ENERGY STAR CERTIFIED COOL ROOF COATINGS
Wailuku, Hawaii Cool Roof Applications
Save money while protecting the environment – that is what a cool roof accomplishes. Utilizing the right coating product can beget heat reflectivity and energy efficiency. In a similar sense to wearing light-colored clothing on a hot day, roof coatings can provide solar-reflective surfaces to maintain lower roof temperatures.
During warmer summer months, temperatures can reach 170° degrees F on traditional dark roof such as a low-slope black asphalt roof, and they can drop to -20° degrees F during the winter in northern and higher elevated regions. Much of the heat generated by absorbing the sun’s ultraviolet (UV) radiation transfers to the building interior, and can have significant adverse effects on energy consumption.
Cool Roofing – ENERGY STAR (DOE) 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.
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.
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:
- 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.
Urban Heat Zones / Islands
Installing Cool Roofs in cities can have significant positive impact on the environment. Urban Heat Zones are caused in part by a significant number of large dark colored roofs in urban areas that can reach extremely high temperatures. This macro heat effect from hot buildings and pavement causes smog, increased energy consumption and discomfort to building occupants . A cool roof can help save the environment and save money. Many states offer utility discounts and rebates to building owners who install cool roofs.
Approvals & Specifications
It is virtually impossible to simply look into two pails of roof coating and predict whether one product is going to perform better than another does. For this reason, specific guidelines have been established for testing and approval of liquid-applied roof coatings that provide a yardstick that can measure all products. Products that meet specific standards display that information on the label. Facility owners and managers should look for such markings when evaluating a product to meet a specific need. Some markings indicate whether a coating meets specific standards or has the approval of certifying testing organizations.
Among the important standards is American Society for Testing and Materials (ASTM) D 6083. That standard measures the coating tested against specific physical performance and physical characteristics for viscosity, elongation, tensile strength, accelerated weathering after exposure to 1,000 hours of testing, permeance, water swelling, adhesion, tear strength, and low-temperature flexibility. If met, this comprehensive set of standards should lead managers to an excellent product.