![]() ![]() My partner and I (He is now deceased, God Bless him) are both RCI registered roof consultants and studied this problem extensively. They lasted 25-30 years without exception. My dad and I installed thousands of squares of organic 240 lb per square organic three tabs produced by GAF in the 50, and 60,s Most over cape cods with vaulted ceilings and no insulation. This happened in the late 70's with the oil shortage and the use of fiberglass felt, that could be coated with very little coating asphalt, and would not absorb water and claw like organic shingles. Result: The ventilation issue was used as a scapegoat by shingle manufacturers that drove down the quality of their product to the point where it did not perform. Result: There was about 5 to 10 degrees difference between a ventilated, and a non ventilated deck.Īny roofing product that fails due to a 10 degree difference in temperature is not qualified to be called a roofing product. Thermocouples were placed under the deck, within the roof system, and in top. Blistering in any bituminous laminated product is caused by moisture trapped within the matrix of the product.Īn extensive program with respect to below deck ventilation was carried out in ORNL (That would be Oak Ridge National Laboratories) by their scientists and engineers with respect to fire retardant treated plywood. Your claim about lack of ventilation below the deck causing blistering is absolute hogwash. ![]()
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