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Community and Q&A

Use foam “fluff” as attic insulation?

Passivist | Posted in General Questions on

A facility near me apparently cuts up a lot of XPS foam and advertises the remains on craigslist for free. They have huge bags of about 4″x4″x1.5″ chunks and others they refer to as “fluff”. They’re just very small, finely ground up pieces of the foam. Since this is free, I was wondering if the “fluff” could be used almost like cellulose in the attic or if the fact that it is no longer solid would greatly diminish its insulating abilities? Thanks for any advice.

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  1. GBA Editor
    Martin Holladay | | #1

    With all those air spaces between the blocks of insulation, I'd imagine that the R-value of these scraps is very, very low. The scraps are probably worth what you pay for them.

  2. Passivist | | #2

    Sorry, I don't really mean using the larger chunks for that purpose, I was just stating what they had. I was really only referring to the very small pieces or "fluff". Hopefully you can see the bags of "fluff" in the attached photo. Thanks!

  3. GBA Editor
    Martin Holladay | | #3

    The fluff looks like it might be usable -- as long as the fire safety issue is addressed. It's possible that this fluff has different (more dangerous?) burning characteristics than rigid foam board.

    I'd want to run the idea by your local building department. If you put it in your attic, capping it with 4 to 6 inches of cellulose would make it safer.

  4. Passivist | | #4

    Yes, I figured it would be a supplement to cellulose, not a replacement, where it could be intermixed with or thrown down before the cellulose. Thank you. I'll check into the fire issue.

  5. Expert Member
    Dana Dorsett | | #5

    At about 3" of thickness most cellulose products would (some have actually been certified to) be an adequate thermal barrier against ignition for polystyrene foam insulation.

    The R/inch for XPS crumb / fluff is probably on the order of R2.5-R3 per inch, which is fine if you have the space. But like EPS, installing it in an open-blow configuration is a bit awkward, since it's WAY too static-ey for most insulation blowing equipment, and would become electrically charged in the process, with bits of it sticking (temporarily) in all sorts of places unintended. Shoveling it into place is probably fine, but more time consuming than with an insulation blower.

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