Air gap between reflective "insulation" and drywall

Old 01-28-02, 09:05 AM
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Air gap between reflective "insulation" and drywall

What is the required/recommended air gap between a reflective surface, such as a foil covering on polyisocyanurate, and the drywall. I just talked to my bldg inspector and he could not give me a definite answer, maybe there is no code requirement on this in Park County CO. Anyway, I would like to know what would be most effective. Thanks Ray
Old 01-28-02, 11:43 AM
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You can go to U.S. DOE fact sheet on Radiant Barriers and it will give you answers on it. From what I read, the space should be about 2 inches. You'll also notice that the field testing is considered incomplete by industry standards. This is because it takes years for data collection, observation and analysis to come out. There are tables that can estimate effectiveness, however, you will note that it is based on incomplete testing. From my experience in the past using these type of tables, the figures are not that far off from the final tables that will eventually come out.
Old 01-28-02, 03:40 PM
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Thanks for help. The DOE report was helpful but seems almost exclusively dedicated to cooling savings where I am interested in heating savings. I do not plan to spend any extra money as quite a bit of the polyisocyanurate that I have obtained
at a very reasonable price all ready has a reflective foil coating on it. I know this foil "works" cause I can stand beside it with the sun shining and feel intense reflected heat. However, I also realize that this foil is metal and might actually conduct heat away if touching or too close to other conductors. The DOE report installation section showed exactly zero installations for heat saving. I noticed that the TVA did a study and I have a relative by marriage who might could get some of the study's results to me. Thanks Ray

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