What can I do with foil-backed poly-iso rigid foam insulation?
December 6, 2017 9:50 AM   Subscribe

I have two full sheets and some scraps of Rmax Thermasheath poly-iso with foil on both sides. After some research including an earlier AskMefi, I realized it was NOT the right thing for sub-grade basement exterior walls, due to the vapor barrier which will be a place of condensation. So what is it good for?

I'm in Portland, OR, climate zone 4C, avg. winter temp 41 degrees F, summers very dry. The basement is all heated living space except for one laundry/utility room

I also have a bunch of fiberglass batting pulled out of walls. Do I need to throw this all away, or can I reuse it? What about these specific possible uses?

1) insulating above grade exterior walls in my drafty old (1900) wood house?

2) celing insulation between my basement and main floor, which is mostly for sound?

3) insulating the interior wall between the heated basement living space and the unheated basement laundry room next to it?

4) insulating the ceiling/floor between that unheated basement laundry room and the bedoom/hallway above it?

5) same as #4 but only in the joist gaps above a continuous, sealed sheet of XPS that hangs below the ceiling joists?
posted by msalt to Home & Garden (3 answers total)
Perhaps not all that helpful, but you could make your son an Iron Man halloween costume.
posted by Wilberto at 10:47 AM on December 6, 2017 [2 favorites]

Best answer: Poly-iso is not for use below grade for other reasons.

You can use poly-iso for:
1 on the inside of the house, 3, 4 on the heated side, 5

You can use the fiberglass for the following so long as it isn't moldy. It doesn't go bad.
1, 2, 3, 4
posted by flimflam at 11:04 AM on December 6, 2017

Response by poster: Thanks!

Wilberto: hilarious but I have only daughters, who are college age, so I don't think that's gonna fly.
posted by msalt at 2:00 PM on December 7, 2017

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