most roofs are composite shingles that are held onto the plywood because a roofing guy used a high powered nail gun to slam a nail throughthe shingle, tarpaper and plywood. This means when you are installing a radiant barrier in a tight crawl space, you have infinite opportunities to scrap your scalp on them.
I was reminded about this by the last guy who helped me install some foil. after lifting his head up and into several nails, he turned to me and pointed to the nails, "Those hurt! Did you know those nails were there?".
As a matter of fact, "Yes". I have the pinpricks on my scalp to prove it.
Be advised. When crawling around in a dark attic, The plywood is NOT your friend.
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