Letters

Reader disagrees with coatings article

Although I respect the good work done by NRCA and Professional Roofing, I found "Myth busting," April issue, page 36, by NRCA Director of Technical Services Maciek Rupar, discouraging.

Although being so negative in each (valid) point of consideration, Rupar misses entirely why there is so much interest in and use of coatings. The reasons for interest include enhancing roof system service life, reducing energy and heat loads, reducing waste and bringing roofing professionals into long-term service relationships with clients.

We have extensive experience with coating asphalt mineral-granulated roof coverings, polymer-modified bitumen, asphalt cap sheets and asphalt shingles. The trade's reaction to such efforts about 40 years ago was vehement, vitriolic and ignorant. We literally were called "communist" because we found coated roofs appeared to have indefinitely extended service lives, which went against those "entitled" to replace roofs every seven to 10 years.

Given the overwhelming change in responsibilities toward lessening energy waste, the coatings issue should be considered more seriously. Coating a roof reduces its surface temperature reasonably close to air temperature.

As with all efforts, some dampening of enthusiasm should be reflected upon, as well:

1. A brittle, burnt-out roof is no candidate for coating.
2. Coating will not salvage a poorly detailed, flashed or constructed roof system.
3. Coating can be as expensive as a simple replacement.

Reasons appropriate for coating include:

1. A client bought a building with a new roof or one in good condition that has objectionable colors, such as pink or green.
2. A dark roof or black roof heats the attic or ceiling spaces to oven temperatures.
3. All mineral-granulated roofs in good condition will have long expansion of service life, and ultraviolet rays will be kept off the asphalt exposed in between the granules.
4. The manufacturer of a granulated roof covering failed to embed or bond the granules, and they are falling off. Such roofs will have short expected service lives.

I would advise Rupar to read "Can Acrylic Coatings Save Your Next Roof?" by Robert Antrim, Cynthia Johnson, William Kirn, Walter Platek and Karen Sabo. Cogently explained is why and how granulated roof systems decay. Each step of the way provides food for the many bugs that feed on roofing materials. The paper confirmed my 25 years' experience and experiments with coatings at the time the article was published in 1994.

Thermal loads on roofs, flashing and decks in much of California and the West are ruinous to durability and pocketbooks. Metals fatigue, fasteners pull out and roofing materials split at 160 F or more. Our coating efforts on such roofs have indefinitely extended roof system service lives.

Even a white granulated roof has large enough exposure between the granules to heat up. Coating such a roof protects the bare areas from decay and cools down a white roof.

But the cost of coatings can add up quickly. Coatings cannot rescue a bad roof system. We found the following process economical:

1. Install a heavily watered down water-based coating as a primer. This will flow between the granules without making a lumpy mess and "prime" the surface. Seek out paint dealers for discontinued colors or mistakes that can be bought fractionally of retail. Our costs for distressed coatings were less than $1 per gallon.
2. Do not use elastomerics because they are expensive and shingles will move regardless. Elongation is not needed. ­­­Elastomerics are appropriate on foam and roll roofing when correctly selected.
3. Most people will not accept a white shingle roof. Look to a soft brown gray. Color coverage will be better and cheaper.

It must be noted that poor durability of dark, poorly ventilated roof systems and roof decks leads to rapid deterioration of roofs. The results are embrittled or broken shingles, shedding granules and hot attics.

I believe the other objections to coating, such as drainage and permeance, are bogus. Spraying or rolling over shingles will not effectively dam water under them. Heat movement and expansion will open up the edges. Coating helps durability: Wet backsides of shingles and their paper-based armatures will swell and degrade quickly.

Fire rating concerns are valid, but a little reason should be taken with objections. Acrylic coatings do not lessen the two aspects of burning or heat from above. The pigments used are quite fire-resistant. No solvent-based materials should be used as coatings. Mastics used with shingles and provided by manufacturers have a low melting temperature and burn quite well. Class A roofs are not fireproof; they merely provide some delay to allow brands to burn out or the fire department to arrive.

In short, coating enhances roof system durability and coolness tremendously and should have better research and industry commitments behind it. The industry needs to recognize the future in roofing will come along with much more commitment to durability and energy conservation. The days of throwaway roof systems are limited. Tax recognition of these values would be a great help to landlords (such as myself) who are penalized for installing superior roofs at tax time. Limitations to coatings are more down to earth than the article mentions. Realistically, everything that provides value is neither free nor cheap.

Rupar points to the need for more specific research but misses the flow in the market. There is a real need for such products, and a lack of consideration in the end does not protect the industry; it limits it.

Karl Kardel
Karl Kardel Consultancy
Oakland, Calif.

Rupar responds: I want to thank Kardel for taking the time to offer his thoughtful letter. He shares useful information about issues not addressed in the article.

Kardel raises the subject of research into enhancing roof system durability with coatings. To my knowledge, no more results from research into field coating applications over asphalt shingle roof systems have been released since the report he references.

The study investigated coating applications over an organic asphalt shingle roof system and glass-reinforced built-up roof system. The report's authors recommended conducting related research with glass-reinforced asphalt shingles. I agree with Kardel that the roofing industry would benefit from similar research as it looks to become more sustainable.