I'm the kind of person that I don't quote facts until I can find something verifiable, not even if it might help somebody because if it'a a hoax, it could be detrimental.
I have a favorite community with 6 builders in it, 2 are right across from each other so they tend to talk against each other, in a professional competitive way. Mr. New Home Sales Rep informed me that the other builder's choice to spray foam will void my client's roof warranty. He even had a hand out from a roofing association. I told him that Resnet recommends it and he deflected. I'm not happy about the possibility of a voided warranty. I love the other builder. They have won green building awards for several years. I've got to investigate for myself!
I am not a builder, nor do I profess to know everything, but I am in the remodeling business as an ancillary part of my real estate business and I take the time to research facts. I know we are to sell the dream, but by being a GREEN Realtor and an Ecobroker I hold myself to a high standard of green knowledge, which means knowing something about environmental building sciences; the envelope so to speak. If somebody asks me what's better, cellulose or spray foam? or asks about re-barb or post tension? I try to stay in the know to best answer the question.
I contacted my resources and had a difficult time. The crux of the matter is that roofers know roofing, and insulation knows insulation, but they don't drill down into either side. How then can anyone state "Warning, you may not have a roof warranty." Handing me a piece of paper from a roofing organization doesn't mean ALL roofers void them and there are special circumstances. Fortunately, I came across a Q&A session from a spray foam association. I so appreciated the credentials of the person who answered the question, a 40 year veteran of the American Society for Testing Materials - Roofing Committe, not a spray foam guy! Here is what he had to say, and I now fully believe that some roofers are just looking for an "out" from servicing their warranty and that some builders, of the ones who don't use spray foam, are closely watching their margins very tightly and trying to survive in a highly competitive marketplace.
Carl Cash, former Chairman of ASTM Main Roofing Committee
American Society for Testing and Materials
Most shingle manufacturers will warrant shingle roofs with sprayfoam installed to the underside of the roof deck without ventilation. But there are still a couple of shingle manufacturers who do not.
The theory was that the insulation would not allow heat to go into the attic and would increase the shingle temperature, thereby reducing its life expectancy. But, the researches determined that many other factors affected the shingle temperature much more than having insulation to the underside of the roof deck, such as:
1. Climate, How hot is it? Arizona vs Minnesota for example
2. Orientation: Which direction does the roof face, east, west, north or south
3. Color of the roof, dark colors absorb heat, white reflects.
Researchers, engineers and building scientists such Carl Cash, former Chairman of ASTM Main Roofing Committee and Anton Tenwolde of the American Forest and Paper Association, and Joe Listiburek of Building Science Corporation have demonstrated that installing insulation to the underside of the roof deck without ventilation does not affect the life of the shingles and that there is on average only a 2-3 degree F temperature difference of the shingles even in the hottest of climates.
Carl Cash reported that a shingle manufacturer could not legally void a warranty based on not ventilating the insulation installed to the underside of the roof deck. He stated that a warranty exclusion has to be reasonable and consistent with other policies of the warranty.
If order to be consistent, they would only be able to warrant shingle roofs in climate zones similar in temperature to Minnesota, painted white and only facing north. He said he would love to testify in court in opposition to a manufacturer trying to enforce that warranty.
So, let the roofing contractor know that there are other shingle manufacturers, (such as Elk and others) who specifically state that sprayfoam applications are acceptable.
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