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Industry Group Sees Dangers in Coating of Asphalt Roofing

Tuesday, January 4, 2011

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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.

roof-coatings

“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.”

   

Tagged categories: Coating failure; Reflective roof coatings; Roof coatings

Comment from Joseph Dandelé, (1/5/2011, 9:34 AM)

We have been engaged in the field of roofing serving industrial, commercial and institutional clients for over 50 years. Roof coatings for asphalt shingles is not a new venture and success depends largely on the application methods used and the vehicle used in the material being applied to the shingles. We do not recommend and coating of any kind for asphalt shingles. Owners should go to light colored shingles if they wish to reduce heat in the interior of there structure. Joseph H. Dandelé Dantech Building Technologies Inc. Markham, Ontario L3R 9R6.


Comment from Phil Kabza, (1/5/2011, 10:03 AM)

As the very knowledgeable comments to the previous article state, "the devil is in the details" (see http://www.durabilityanddesign.com/news/?fuseaction=view&id=4857). Unfortunately, the details of the "Myth Busting" article cited above are a mixed bag. Knowledgeable consultants and applicators don't recommend solvent-based coatings on asphalt shingles. Nor do they recommend application of high-build "waterproofing" coatings or membranes on asphalt shingles. No knowledgeable consultant or applicator would recommend using power washing on asphalt shingles. However, proper application of a highly-reflective, compatible coating on a roofing substrate in good condition can have positive advantages as described in the comments mentioned above, which include lowering air conditioning loads and extending roof membrane life by reducing thermal stress. An experienced coating applicator will verify existing conditions and compatibility on any substrate before performing work. I don't think it places the NRCA in good light to mix wisdom with half-truths in a public statement on this issue; better that we get their excellent technical capabilities behind determining what coatings work where, what we should avoid, and help educate homeowners about working with qualified applicators and consultants. It could just be that the lawsuits FPL is facing will be dismissed once information becomes available about the age of the roofs that failed following coating, and the materials and practices used by the applicators. "The devil is in the details."


Comment from Karl Kardel, (1/5/2011, 1:05 PM)

I have direct experience with coating of asphalt shingles and BUR roofs for over 40 years. Using a two coat thinned down acrylic we have seen roof life extended for about two decades. The coating is to protect the shingles from u.v. which bounces around between grannules and deteriorates chemically the asphalt.Next the surface temperatures are dropped to near air temperature as oppossed to 150 degrees F. This in not a panacea, and it does not renew a tired roof. Elastomerics with a heavy film are a bad idea and a waste. Snake oil claims for 'nano' coatings are just that. Bunk. But coatings can have an excellent benefit in reducing a.c. costs and extend sometimes indefinintely roof life. I have written and been responded by NRC that their response is 'knee jerk' and really reactionary. It stands in contrast with their great work on standards and truth about mfrs. smoke on quality.


Comment from Eric Swanson, (1/5/2011, 1:33 PM)

I'm just a paint chemist and I don't make roof coatings. However, I am very familiar with flexible acrylic roof coatings. I guess I look at this as 'fear propaganda' from the people who would rather see people buy new shingles instead of using a coating to preserve the life. It's really easy to say that you can't duplicate claims. Can you say that you can disprove them? Why not? This seems like the old 'sow a little doubt' strategy. I have problems with articles that are filled with half truths and fear mongering without proof. In addition, I think if you are going to paint that fear then you should explain the various failure mechanism theories for each failure mode. Based on the way this article is written, I am swayed more to disbelieve the author's conclusions than to accept them. So, for roof coatings on asphalt shingles... I say... 'Plausible' For this author.... I say... 'Busted'


Comment from David Lawson, (1/5/2011, 2:14 PM)

Thank you Eric for your straight forward to the point comments! I couldn't agree more. I couldn't decide who to be more critical of, the Roofing Manufacturers Association, the author who wrote such a poorly researched article or those who choose to rush to litigate instead of using common sense.


Comment from Tony Abruzzese, (1/5/2011, 3:51 PM)

Kudos to Eric for the most rational and accurate thought process regarding this tremendous amount of misinformation. Does one really have to wonder why the NRCA would be against coating roofs? I would certainly hope not. As a 3rd generation applicator, and now formulator and manufacturer of roof coatings, I can guarantee that the best type of coating for a shingle roof is actually and elastomeric coating. This would, of course, be a true elastomeric and not some of the watered down whitewash that happens to have elastomeric on the label. It is an unfortunate truth that even the best materials, if applied incorrectly, can actually cause roof leaks in an otherwise sound shingle roof. If the entire surface is not coated to a minimum of 20 mils DFT, leaving no pinholes whatsoever, then water can intrude and not escape due to the dam created by other areas that are coated completely. This is undoubtedly the most probable cause of the unfortunate damage to the homes involved in the lawsuit. When an elastomeric is properly applied it covers the entire surface much like a seamless sheet of plastic. This will not only repair leaks, but prolong the life of the roof system indefinitely. No wonder the roofing industry would use any tactics they can to cause fear by perpetuating misinformation and half-truths. T.A., Hy-Tech Thermal Solutions.


Comment from Bill Mann, (1/5/2011, 8:58 PM)

Phil, Karl, Eric, David and Tony all hit the nail on the head. Elastomeric acrylic coatings do indeed work over asphalt shingles, however, a successful application depends on proper substrate preparation along with quality workmanship and materials. Conversely, poor quality installation and/or coatings are most likely not going to perform over shingles or any other substrate for that matter. Rohm and Haas did extensive testing with their Rhoplex 1791 resin over asphalt shingles at their Spring House, PA facility in the 1980's and proved beyond a doubt that the application was effective in extending the life of the roofing system. The coating sealed and waterproofed the shingles, preventing further degradation of the asphalt and loss of granules. Reflectivity at that time was not so much an issue, but has since become an additional benefit. Our company has sold acrylic coatings for use over shingles for many years, including numerous military installations, without any problems. At one time we marketed an acrylic coating specifically for use over shingles, but eventually pulled it off the market; not because it didn't perform, but for liability issues related to the increased slickness. A quality acrylic elastomer, properly applied over a suitable asphalt shingle substrate (which would be one that is sound and fully adhered) is most definitely effective in extending the life of the shingles and providing additional reflectivity values in lighter colors. B. Mann, United Coatings


Comment from Steve McGuinness, (1/17/2011, 1:45 PM)

The real problem might be that the elastomeric coating to too efficient. It works too well at cooling the roof surface. Something to consider, an elastomeric roof coating is extremely efficient at reflecting heat energy from the sun. When applied to a residential shingle roof, it will make the roof deck cool, both the roof surface and the deck inside the attic. A typical residential roof has vents along the eves and the ridgeline. These vents encourage air convection through the attic; the roof gets hot, heats up the attic and convection occurs. After an elastomeric coating is applied to the roof shingles, the roof does not get hot… Convection does not occur. Now you have a situation where warm moist air is entering the attic through the eve vents but there is not convection. This warm moist air condenses on the underside of the roof deck, because the roof deck is so much cooler than the air. This condensation will saturate the roof deck and cause mold, mildew, and rot. Possible solutions would be to put power vent fans on the roof or gables to move to encourage air movement. If the air circulates through the attic, it will not have a chance to condense on the roof deck.


Comment from George C. Keefe, (1/18/2011, 3:31 AM)

As with most things in life, one size doesn’t fit all and roofing is no different. All roofing situations should be dealt with and evaluated on a case by case basis. There has been continued success in rejuvenating and extending the life of all roofs with coatings, this includes asphalt-shingle roofs. What coatings are used, when they are used and where they are used along with surface preparation and installation methods should be chosen accordingly. Taking what is good about the existing roofing materials, their strength and insulation R-Value and adding to it with coatings that will extend their life makes good sense. If the roof is coated with lighter colors they become solar reflective creating energy savings and repelling heat. Coating also takes a roof surface that has many problematic seams and gaps and turns it into a continuous, monolithic casing. The fact that old roofs can be rejuvenated and don’t need to be torn off and replaced instead coating over them and extending their service life is something that is appealing on several levels. Studies show 42% of CO2 emissions causing green house gases contributing to Global Warming/Climate Change are coming from overflowing landfills and this should be of concern to all of us. Coating over a roof and extending its life stopping the generation, transportation and storage of unwanted waste is environmentally responsible. With all these positive attributes roof coatings for all roofing including asphalt-shingle roofs cannot be ignored and the reality is they are here to stay. George C. Keefe GLOBAL Encasement Inc. AKA Encasement Guy


Comment from George C. Keefe, (1/18/2011, 3:31 AM)

As with most things in life, one size doesn’t fit all and roofing is no different. All roofing situations should be dealt with and evaluated on a case by case basis. There has been continued success in rejuvenating and extending the life of all roofs with coatings, this includes asphalt-shingle roofs. What coatings are used, when they are used and where they are used along with surface preparation and installation methods should be chosen accordingly. Taking what is good about the existing roofing materials, their strength and insulation R-Value and adding to it with coatings that will extend their life makes good sense. If the roof is coated with lighter colors they become solar reflective creating energy savings and repelling heat. Coating also takes a roof surface that has many problematic seams and gaps and turns it into a continuous, monolithic casing. The fact that old roofs can be rejuvenated and don’t need to be torn off and replaced instead coating over them and extending their service life is something that is appealing on several levels. Studies show 42% of CO2 emissions causing green house gases contributing to Global Warming/Climate Change are coming from overflowing landfills and this should be of concern to all of us. Coating over a roof and extending its life stopping the generation, transportation and storage of unwanted waste is environmentally responsible. With all these positive attributes roof coatings for all roofing including asphalt-shingle roofs cannot be ignored and the reality is they are here to stay. George C. Keefe GLOBAL Encasement Inc. AKA Encasement Guy


Comment from Karl Kardel, (1/19/2011, 7:27 PM)

Cool Roof Mythbusting by Rupar makes some new myths. There has been a wide array of studies. The most informative published by RSI- Oct. 1995 (Antrim, Johnson et al)explains the chemical process by which sun degrades asphalt shingles. The spaces between grannules is bare asphalt. Counting the sides of grannules you have a lot of surface area to reflect onto the asphalt. Coating roofs interrupts this process and enhances service life. The amount of savings on a.c. due to cool roofs is exhaustively documented. Coatings however are likely to be more expensive per pound than roofing. Thus saving a dead roof is not worth the materials needed to do so. Also the problems of dirt gathering are not addressed by the supporters of cool roofs. Keeping roofs white may be a job, but the savings in durability and a.c. costs are known. Sloped roofs tend not to collect the amount of dirt low slope roofs gather. But after 40 years of carefuly and selectively coating roofs, we have experinced no negative results. Only longer lived, cooler roofs.


Comment from David Lawson, (1/22/2011, 3:22 AM)

RE: Comment from Steve McGuinness, (1/17/2011, 1:45 PM) Your explanations would require very specific conditions to be in place. Perhaps you might give an example that is scientifically supported. Without specifying what the environment conditions are you make general statements that cannot be true in all cases. You state that "condensation will saturate the roof deck" How do you know this and when might this take place, summer, winter? Can you explain this in terms of relative humidity and dewpoint? For condensation to occur there would have to be a fairly significant difference in the ambient temperature of the attic and the temperature of the underside surface of the roof deck especially during a heat wave. You don't take into account that the attic will allow heat to enter through the venting. If the attic is indeed as cool as you say then the laws of thermal dynamics dictate that the warm outside air will flow into the attic space where it is cooler. This transfer of heat is called convection. If this is the case then the attic surfaces will not stay cool to the degree that condensation will occur as the abient temperature would have to even out eventually as would the underside of the roofing deck.


Comment from scott bowlan, (7/5/2014, 6:46 PM)

this is a bunch of union companies are posting bs stories on the facts. as long as there is one inch on all sides there is a vapor escape rout. I am a chemist and this story is designed as a deterrent to stop the sales of roof coatings so the contractors union doesn't loss cash. they have been scrupling people for years and they are protecting their best interest.


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