All About Roof Coatings
Roofing choices often come down to system economics, owner preferences, or the specifier’s experience. Often, a lack of awareness about roof coatings as an alternative option can result in a compromised choice for the long term.
A long-term, economical roofing solution often overlooked is elastomeric roof coatings. In the US, California’s Title 24 law has increased awareness of the energy-saving benefits white or “cool” roof coatings offer but the education of the positive attributes of roof coatings is just starting in Canada. These roof coatings, applied to traditional flat roofing or steel or metal roof systems, comply with new regulations or help a building obtain ENERGY STAR® or LEED Green Building Rating System® certification.
Building owners and facility managers are starting to realize the lasting benefits of elastomeric roof coatings. These durable, liquid coatings prolong the life of the existing roof. In fact, elastomeric roof coatings have been used since the early 1980s over multiple roof types, including BUR, modified bitumen, metal, cement, EPDM and wood. Many white-coated roofs exist today with excellent adhesion and high solar reflectance – more than 20 years after their initial application.
An elastomeric roof coating creates a uniform, seamless surface that remains flexible even at low temperatures. It expands and contracts with changing weather conditions, protecting a roof’s surface from the sun’s damaging rays. This enables the coating to handle the continuous thermal stresses over the lifetime of the roof. Its adhesion characteristics enable the coating to remain attached to the roof in wet or extremely windy conditions. Such a coating employs technology (to resist dirt pick-up) that helps maintain energy-saving reflectance qualities, as well as a bright, clean appearance.
On existing buildings, elastomeric roof coatings do not add “dead load” or weight to the roof. The roof coating can be applied without being counted as an additional layer for code purposes. This mitigates the cost of disposal from tear-off and contributes to dollars saved by the building owner.
Finding ways to increase the service life of roofs makes sense to owners and reduces the waste generated by roof tear-offs. Statistics compiled by the US Department of Energy and Environmental Protection Agency show that waste generated from roof tear-offs accounts for 15%-20% of total landfill waste. By coating and maintaining roofs, one can dramatically increase the years of service they can provide.
For most roof systems, roof coatings renew the integrity of the surface of the roof by filling in cracks and replacing weathered and worn areas. Roof coatings reinforced with membranes such as polyester or fibreglass can seal and waterproof a roof. They can also improve reflectivity and emissivity while reducing thermal shock. Coatings can extend the life of low-slope and flat commercial roof types for many years while reducing energy consumption, thus saving the owner more money.
With high-energy costs here to stay and building energy efficiency standards tightening, qualified reflective roof coatings will remain as one of the most effective and most economical ways to meet or exceed these emerging standards
Coatings Extend Roof Life
A elastomeric roof coating can extend a roof’s life by:
Creating a UV light barrier, which prevents substrate degradation.
Resisting blistering under extended water ponding.
Providing low-temperature flexibility.
Developing a high degree of adhesion.
Reducing daytime roof temperatures.
And, the choice of high-quality coatings, as designated by ASTM D-6083 performance standards, can assure long-term performance and protection of the roofing substrate.
Longer Roof Life
According to the Roof Coating Manufacturers Association, high temperatures can shorten the life of rubber, synthetic polymer, and especially asphalt roofing systems. The rate of degradation begins to accelerate even at a “modestly elevated” 140° F, causing “significant damage” and affecting both short- and long-term performance. Their rule of thumb for thermal aging is that service life is cut in half for every 18° F increase in temperature. Cool roof technology utilizing elastomeric coatings greatly reduces heat build-up where it starts.
To ensure proper performance from an acrylic roof coating, specification ASTM D-6083 (Standard Specification for Liquid Applied Acrylic Coating Used in Roofing) was developed to define a suitable level of quality. The tests and standards are based on actual in-service performance cases of acrylic roof coatings from numerous manufacturers over various roof types, ranging in age from a few years to 20 years, on roofs located throughout the United States. Anyone using a coating that meets this standard can have confidence that the elastomeric roof coating will perform successfully when properly applied over a sound roof.
