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Community and Q&A

Bubble wrap as knee wall barrier only

ErnieVF | Posted in Energy Efficiency and Durability on

I understand the argument against bubble wrap as radiant barrier and duct insulation (and agree) but how about as a knee wall air barrier? edges and seams are air sealed of course, it is easier to get in attic hatches, and can be attached with a slap stapler. I know rigid air barrier would have more R-value, but is there any possible moisture issue or negative effects of bubble wrap on attic knee walls? Thanks!

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  1. Expert Member
    BILL WICHERS | | #1

    Bubble wrap is the same as polyethylene sheet if you’re using it as a vapor barrier. The “bubble” part makes no difference. The downside is that bubble wrap tends to come in relatively long, narrow strips but you can get poly sheet in BIG size pieces which makes it easier to install as a single piece for the best possible seal.

    Remember that bubble wrap will have all the same issues as any other vapor barrier if you install it, so take the usual precautions regarding installation.


  2. Expert Member
    Akos | | #2

    Depends on which side you install it.

    Generally in heating climates a cold side vapor barrier that has almost no R value is a really bad idea, putting the bubble wrap on the outside of the wall is asking for trouble.

    On the inside of the wall it should be fine, but it really is not doing anything more than cheap 6 mil poly, not worth the extra cost.

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