I'm trying to understand what the difference is between the high dollar
stuff that these insulating companies sell and plain aluminum foil, other
than the reflectivity might be higher. Right now I'm thinking about just
trying an experiment with a few boxes of aluminum foil by stapling it to the
rafters with the reflective side toward the roof. Please let me know the
fallacies of this if there are any. Thanks in advance.
But if you mount it shiny side down, that defeats the purpose of keeping the
radiant heat from your roof out of the house. In that case it would only
work in the winter, as in summer the heat would still penetrate from the
outside. Am I correct on that?
I've heard of shiny side down too but it doesn't make sense to me either. I
bought the paper backed foil that is applied to a house before vinyl siding
is put on. Joe's right about the degadation of the reflectivity due to dust
but in addition to that there is oxidation of the foil, which is quite thin.
After 10 years up there I don't believe that it's doing much good. For that
matter, I don't feel that it ever did any good. One caveat on my
application, however. I laid the foil on top of the insulation batts and
not to the rafters as the OP notes. That may make a bigger difference since
the foil would be closer to the source of the radiated energy. It has been
my thought that foil applied to the rafters would degrade the shingles more
quickly. Just a tought.
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