What amount of heat savings can I expect using reflective shield in my attic over twelve inches of fiberglass insulation? The house was built with 6″ craft faced fiberglass between the joists, to which the previous owner added blown in cellulose(?). There is no flooring, there is no AC ductwork or exposed wiring. Our heat cost is very high in central NV (AC season is short). Along comes a man promoting his radiant barrier product consisting of two layers of aluminum foil with about 1/8″ bubble material between the two. The product features holes about 1/8″ in diameter every 1 1/2″ apart. He proposes to simply lay the product over the existing blown in insulation and guarantees a 55% fuel savings. I have my doubts about the savings, but my real concern is moisture and then mold being trapped under the radiant barrier. Will the cellulose plug the holes? Would I be better off adding unfaced fiberglass roll over the top of the cellulose?
My senior neighbor needs her roof replaced. Because she has composite shingles over original wood shingles, the roofer plans to remove all the old shingles, but not the wood laths to which the wood shingles are attached. The roofer plans to install radiant barrier decking over the laths. However, another opinion is that the radiant barrier is more effective if the laths are also removed and the radiant barrier decking is installed directly to the rafters. Please advise whether the laths should be removed before the radiant barrier decking is installed.
Under the “Myths and Misconceptions,” you say it is fine to install reflective insulation over existing mass material. I assume this means the rolled fiberglass I have in the attic now. I was reading somewhere else that applying it on top of the fiberglass can trap moisture and it is not recommended. I do understand, and you as well as another source, say dust can render it ineffective. My house is 34 years old and I want to add insulation to the existing insulation layer. The attic is tight – you definitely can’t stand up. Is a radiant or reflective the best type for me? It is a 1400 sq. ft. house including the garage. A salesman was at the house today and showed me a sample of his product. It was extremely thin. Home Depot has rolls that look like foil bubble wrap. Just how many different reflective barrier products are there?