FAQ: Will a radiant barrier work when installed under my new asphalt shingles?
ANSWER: No. A radiant barrier MUST be facing an air space for it to reflect the radiant heat. Without an air space on at least one side of a radiant barrier, radiant heat will conduct all the way through it as if not installed.
This question is asked more often these days as more roofing contractors and builders begin capitalizing on the ever-growing reflective radiant barrier market.
It appears that a few companies out there are promoting the ill-advised addition of a radiant barrier directly under asphalt shingles. This method of installation will not provide any benefit since a radiant barrier reduces the transfer of radiant heat that travels across an air space. Placing a radiant barrier directly under shingles provides no airspace therefore NO BENEFIT!
However, there are some roofing products that actually create an air space when installed. Such products include clay tiles, corrugated metal, and similar products with inherent ridges. Installing a radiant barrier under one of these products would be beneficial since portions of the radiant barrier would be adjacent an air space.
Another way to gain an air space under a roofing product without an inherent air space, such as slate tile, would be to install with a batten or counter-batten system. Battens are made from wood, plastic, or metal and are installed horizontally or both vertically and horizontally (counter-batten system) to which to adhere the roofing material. Attaching a radiant barrier to the top of the vertical or horizontal battens before installing the slate tile would give the radiant barrier the air space required for it to be effective.
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