Cool Roof Coatings
Cool Roofing – ENERGY STAR (DOE) qualified roof coating products reduce the amount of air conditioning needed in buildings, and can reduce energy bills by up to 50%. The Cool Roof Program defines certain standards for solar reflectance, 3-year aged maintenance of reflectivity, and emmisivity 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.
|Reflectance = 5%
Temperature = 180°F
|Reflectance = 29%
Temperature = 157°F
|Reflectance = 60%
Temperature = 128°F
|Shingles with lighter/whiter color or roofing granules reflect the solar heat.|
Lighter colored (white) roof coatings reflect the suns heat and UV rays and often 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:
During warmer summer months, temperatures can reach 170° degrees F on 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.
Urban Heat Zones / Islands
Installing Cool Roofs in cities can have significant positive impact on the environment as well. 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.