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I have interior walls that are 24OC and I'm insulating them with 15.5 OC Denim/Cotton batts (they don't make a 23/24" version of this insulation)

Because they're interior, normally a friction fit would be used. However, it seems that using 1.5 batt width as a friction fit seems unstable.

Any ideas on how to make this happen without having to put drywall up on the opposite side? Insulation ties, insulweb, anything else?

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    Yeah. Buy the correct width batts for 24" studs instead of trying to hack it with batts made for 16" stud centers.
    – Michael Karas
    Commented May 31, 2016 at 5:40
  • They don't make 23/24 batts for this kind of insulation
    – tjcinnamon
    Commented May 31, 2016 at 12:14
  • OK. Then the next obvious question is why not select some other type of insulation. Why use "denim/cotton" insulation at all?
    – Michael Karas
    Commented May 31, 2016 at 12:24
  • Because it has sound proofing qualities and I'm using it in the joists which are 16OC but I'd like to use it on some interior walls which are 24OC
    – tjcinnamon
    Commented May 31, 2016 at 12:26

4 Answers 4

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From the comments it sounds like you have drywall on one side. I'd set up a measuring jig to give consistent, square cuts, and cut your batts to length so that they fit well horizontally. Stack them in the stud spaces.

If necessary, apply a sheeting over it to give additional support. Something with a textured surface might be preferable to polyethylene because it will give additional friction support.

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  • I don't have the drywall up yet. Drywallers are coming Thursday and I need to insulate prior to that
    – tjcinnamon
    Commented May 31, 2016 at 14:17
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    I'd either coordinate with them to do one side and then move to other areas while you insulate (you'd have the pieces pre-cut), or apply paper to one side, insulate, then paper the other. The key is to cut the batts to length and stack them.
    – isherwood
    Commented May 31, 2016 at 14:53
  • I may lay the extra drywall because it's in an unfinished space outside the interior walls. I'll have to look up what a measuring jig is
    – tjcinnamon
    Commented May 31, 2016 at 14:56
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    Any mechanism that allows consistent and efficient cuts. Could just be a framing square and a mark on the floor measured out from a wall.
    – isherwood
    Commented May 31, 2016 at 15:19
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Searching Google for 24" denim batts turned up a ton of options that are available. Here is an example. Using this will be WAY easier than trying to hack 16" stuff together.

If you are pretty intent on going with 16", you could try placing the insulation in the cavity and then stapling 24" wide paper like this over it to hold it in place. If I were doing this, I would probably cut the batts in 4 foot lengths. So I would try to friction fit the two 4' lengths together in the cavity, staple the paper over them, and then work on up to the next 4' length.

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  • I already bought them and most 24OC are not sold in stores and are special order and in some cases the special order requires a minimum quantity. These are ultratouch+ which have more cotton content and are R13 which is what I need for some space constraints in the joists
    – tjcinnamon
    Commented May 31, 2016 at 14:04
  • Great idea in putting them in perpendicular! I'm gonna try that unless someone comes up with something else. I have insulation ties but those bend and wouldn't work well for stud cavities
    – tjcinnamon
    Commented May 31, 2016 at 14:07
  • The above comment appears to belong on @isherwood's answer.
    – Ecnerwal
    Commented May 31, 2016 at 14:43
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Probably too late for you, but when I had a similar issue I wrapped the back in this sheet material before insulating. It was easy to install with staples and then I sprayed foam around the edges. On the inside where some bays were too wide for the insulation that I had at hand, I just put a piece of duct tape across the bay at the top, middle and bottom, to hold the batts in until I got the drywall installed.

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What I ended up doing was similar to what people suggested by putting up a temporary barrier. I waited for drywall on one side (I was lucky to be able to do that because I had an unconditioned space), then I put the cotton insulation in and held it in with R11 kraft faced. Considering it's for sound control the double insulation was not a bad thing (so long as the insulation is not compressed!)

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  • I don't understand. You used two layers of insulation?
    – isherwood
    Commented Aug 11, 2016 at 15:14
  • Yes, it's for sound control as opposed to R value. I put in Kraft Faced for the barrier and Denim for the mass
    – tjcinnamon
    Commented Aug 11, 2016 at 19:02

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