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Can you install batt insulation in the cavity of a double stud wall?

user-5380372 | Posted in GBA Pro Help on

Hi, I’m building a cabin in upstate NY and trying to achieve an R-50+ wall. I want build a double stud wall assembly with Roxul Comfortbatt. I’d like to install a continuous layer of batt at the wall cavity (in addition to between the studs themselves). The manufacturer advised against this. They said the batts won’t stay in place unless secured between two studs. I’ve been seeing examples online however, that suggest you can do this. They show double stud wall, cavity filled with dense packed cellulose or batt – unless I’m misunderstanding. Can anyone advise on this? Thanks in advance.

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  1. AlanB4 | | #1

    "Let us redefine progress to mean that just because we can do a thing, it does not necessarily mean we must do that thing"

    If the manufacturer says its not a good idea, why are you so intent on doing it anyways?
    Would not dense pack cellulose be much cheaper and much more field tested?

  2. Expert Member

    From a practical persecutive I'm wondering what the problem is? Presumably if the cavity is the same depth as the batts, and the batts are installed horizontally, the batts are held in place by the studs and batts of the two walls. Does the manufacturer specifically advise against this, or more generically against using batts in situations outside wall cavities?

  3. user-4524083 | | #3

    Seems like it would work. May be cheaper than dense pack if it's a diy job. Roxul is pretty dense and if held by 2 stud walls would have some friction. I think I'd want to make the space between the studs a little tighter than the thickness of the batts( say 3" space for 3.5" batts) to insure no settling.

  4. gozags | | #4

    I have done this, albeit on a small scale. Have a utility wall that is pretty thick to accommodate some pipes, etc. The friction from 'the sandwich' holds the middle Roxul batt snug. It's not going any place. Not sure how that would scale out throughout a whole house, however.

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