Had a nice talk on the phone with JP Bolton, Vice President of sales of Innovative Insulation. Here's what transpired in email form. I have no affiliation with that company, for the record.
Hello Ross,
You are absolutely correct in your assessment. Tests were conducted to determine the possibility of overheating shingles and causing premature curling and roof system failure. The most interesting aspects of this has been the several contractors who have called me and told me they had OBSERVED this shingle failure situation. THEY WERE LYING!
I have attached the test for your review.
This was the premise: Radiant barrier installed would reflect the heat thereby doubling the temperature of the shingles.
Two identical homes, one with barrier and one without, were subjected to hourly shingle temperature measurements. Over the course of the test we found that during the PEAK HEAT OF THE DAY, the shingles on the home WITH barrier were indeed higher than the home without. Unfortunately for Owens Corning who desired a large temperature problem,the difference was never more than 5 degrees. This is an insignificant increase in temperature for a shingle designed to work any where from dessert to cold climates. More unfortunate for Owens Corning, after the PEAK HEAT OF THE DAY, the shingles on the roof WITH the barrier were as much as 8 degrees COOLER than the home without. Over the course of the test period the home WITH BARRIER had an average shingle temperature 6 degrees COOLER than the home without barrier.
What had occurred was that the home without the barrier had built up a reservoir of heat in the attic during the day and that heat had kept the roof hot re-radiating that heat when the heat source (Sun) was removed. The home with the barrier had never built up a reservoir of heat and had gone ambient as soon as the heat source was removed.
As a result of this test all the shingle manufacturers have issued letters that the installation of radiant barriers will NOT affect shingle warranties. So, next time some contractor tells you that he has OBSERVED this shingle failure, (or vinyl siding failure) due to the excessive heat caused by radiant barrier installation, you might ask him what planet this occurred on because it was not earth.
Please pardon my extreme feelings about this, but I have had several run ins with contractors over this issue and I have a large burr under my saddle over this subject. J. P.
J.P. Bolton
Vice President of Sales
Innovative Insulation Inc.
6200 W. Pioneer Pkwy
Arlington, TX. 76013
800 825 0123
jp@radiantbarrier.com
From: Ross Neag [mailto:jasrwn@comcast.net]
Sent: Wednesday, October 31, 2007 10:21 PM
To: Innovative Insulation Information
Subject: Having a discussion about shingle temperatures and radiant barriers
Hello. I am a customer of yours and a licensed home inspector in Chicago. Some colleagues and I were having a discussion about installing radiant barriers either under the roof decking or to the bottom of rafters and its affect on shingle temperature. I believe that if you are able to keep the inside of your attic noticeably cooler that the only possible negative effect would be the radiant energy bouncing back to the underside of the shingle. I argued it is minimal at best and that some shingle manufacturers would have already voided warranties if it could be proved that RB was used. The reduction in interior temperature and its corresponding cooling effect of other building components, especially the longer amount of time for things to heat up, all play a beneficial part in PROLONGING roofing materials.
I’d like to hear your opinion, either by email or phone. Thanks in advance…
Ross Neag
708 243 7222