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Posted by hallerb@aol.com on April 1, 2008, 10:11 am
On Apr 1, 7:31=EF=BF=BDam, donald.gi...@gmail.com wrote:
> I sat through a free dinner (chicken or shrimp) and heard a guy try to
> sell me roll-out multi-layer aluminum foil insulation (apparently with
> mylar in the sandwich). =EF=BF=BDIt is perforated so as to allow moisture
> through, and installed over top of the fiberglass/cellulose/whatever
> in the attic. =EF=BF=BDIt is claimed to reduce heat gain in the summer and=
> heat loss in the winter.
>
> I don't doubt that it would be effective to some degree, but I gather
> that the optimal placement for heat-gain reflective insulation =EF=BF=BDis=
on
> the underside of roof rafters, and I think that the optimal placement
> for heat loss would be on the warm side of the house in the winter,
> i.e. just behind the drywall, with an air gap. =EF=BF=BDLaying the stuff o=
ver
> 12 inches of fiberglass is optimal for neither situation, but it still
> might be ok.
>
> Does anybody know what increase in effective r-value you might get
> this way? =EF=BF=BDI live in the north and don't use AC, so =EF=BF=BDreduc=
ing heat
> loss is generally more important a consideration. =EF=BF=BDI searched for =
a
> while with google but didn't find anything very relevant.
>
> I have truss rafters, incidentally, and installing this would be a
> total pain in the ass.
with trusses just add more regular blown in insulation.
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