The application of white, “cool-roof” coatings to asphalt-shingle roofs has gotten a Florida electric utility in hot water with some homeowners due to allegations that the coatings caused roof deterioration and leaking, as reported Tuesday in Durability + Design (see Cool-Roof Coatings Generate Some Heat).
A national roofing-industry association might very well offer this kind of reaction to the situation:
We told you so.
The National Roofing Contractors Association’s (NRCA) director of technical services, in an article published early last year, cautioned that field application of coatings to asphalt-shingle roofs may be asking for trouble.
“Roofing professionals long have recognized the viability and advantages of roof coatings for surfacing bituminous weatherproof roof membranes used as part of low-slope roof systems, and possess a great deal of experience with coating applications over roof membranes,” wrote Maciek Rupar, NRCA director of technical services. “This is not the case with field coating steep-slope roof coverings.
“The fact is, the most widely used steep-slope roof covering—asphalt shingles—is not designed to accept or require field-applied surfacing,” Rupar said.
The use of white, solar-reflective coatings often proves beneficial in reducing roof temperatures and contributing to lower cooling-energy demand. But the application of such coatings has been blamed for roof deterioration and leaks in a number of homes in South Florida, where the paint jobs were paid for in part with rebates offered by Florida Power & Light.
The utility is a target in a lawsuit filed by several homeowners who hired contractors to apply the coatings, the result of an FPL program aimed at helping customers reduce energy use. (See FPL sued over program aimed at saving energy.)
Rupar, in his article “Myth Busting: The Risks and Unverified Benefits of Field Coating Asphalt Shingles,” said a number of coating products are marketed as being suitable for application to asphalt-shingle roofs. These products are billed as a cost-effective way to extend roof life, repair leaks and reduce energy costs. But he went on state that laboratory or weathering test data confirming such claims does not accompany marketing or promotional materials on the products.
Rupar cites a number of other problems with the marketing of coatings for asphalt shingle application:
• Common recommendations on cleaning methods often include pressure washing, which is not advised by NRCA or the Asphalt Roofing Manufacturers Association (ARMA), as such washing can damage shingles.
• Claims about “thermal insulating” properties of some coatings products cannot be verified by means of standardized and published test methods.
• It may be “difficult or impractical” to objectively evaluate the physical properties and performance characteristics marketed for applications to asphalt shingles, due to a lack of established test methods and standard material specifications for coatings used in such applications.
“The roofing industry is aware of a number of issues that could have negative consequences for field application of coatings over asphalt-shingle roof systems,” he said. “Anyone considering this type of application should be aware of the concerns so they can weigh them against the benefits claimed in coating product promotional materials.”
Rupar mentions two sources of information on the recommendations of asphalt shingle manufacturers: an ARMA technical bulletin and a technical brief from roofing manufacturer GAF-Elk. Neither endorses the practice of field coating of asphalt-shingle roofs.
Other shingle manufacturers do not make recommendations, or state that application of coatings has a negligible effect on shingles if water-based coatings are used. Hydrocarbon solvent-based coatings are not recommended due to the potential for softening of the asphalt on the shingle.
In a conversation with Durability + Design, Rupar also said coating application can interfere with the water-shedding design of asphalt-shingle roofs.
“Generally, it’s viewed as asking for problems,” he said. “The gist of it is, shingles were never designed to have anything else applied to them.”
In addition, he said a thicker-film coating designed to function as a waterproofing membrane could impede drainage and create stresses on the roof due to effects on roof flexibility and movement.
Rupar cited a number of other factors that could adversely affect asphalt-shingle roofs as a result of coating applications. His article can be read at Myth Busting on Field Coating Asphalt Shingles.
Rupar said he was not familiar with details of the lawsuit filed against Florida Power & Light, although he said he had been contacted some time ago by a lawyer representing Florida homeowners who were pursuing such an action. He said the lawyer was investigating industry research or other information on the issue.
A number of comments have been submitted by readers on the report in the Tuesday (Dec. 4) Durability + Design, including comments on first-hand experience with such coatings applications. See Cool-Roof Coatings Generate Some Heat.
In his “Myth Busting” article, Rupar concludes that “No evidence currently is available to correlate marketing claims with actual performance of field-applied coatings over asphalt-shingle roof systems, and such an application subjects a roof system and its owner to specific risks the owner should understand before making a decision to field coat an asphalt-shingle roof system. A thorough cost-benefit analysis may prove that known concerns within the roofing industry outweigh the potential benefits.”