Faced or unfaced insulation?


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Old 11-21-19, 01:44 PM
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Faced or unfaced insulation?

Installing R-15 fibreglass batts between studs in a cavity separating my shower from an adjoining condo. Doing this for sound dampening as well as insulation purposes. Local hardware store only sold faced batts. I'm in South Carolina. The old insulation was faced and seemed to work OK. There is a little bit of black (mould?) on some of the studs but they're mostly fine. I plan on installing Kerdi Board over the studs. Looking around online at pics like this (https://en.wikipedia.org/wiki/Vapor_...er_replace.jpg) and reading (https://www.energyvanguard.com/blog/...Probably)makes me think I could omitt the kraft paper and tear it off the insulation.......... The Kerdi board is supposed to be 100% water proof anyways (is it vapor proof?). Does it even matter?
 
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Old 11-21-19, 01:58 PM
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It probably makes no difference whether you leave it on or take it off. Usually the vapor barrier faces inside the closure. But in this case it's an inside wall. What's the point of removing it?
 
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Old 11-21-19, 02:11 PM
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Hi Norm201. Mostly wanted to change the insulation for a better sound barrier while I have the walls open. It was about $45 for the new insulation.... And I'm obviously no expert in insulation but you can see in the pic several of the old pieces were cut too small and have huge gaps between the insulation and stud.
 
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Old 11-21-19, 02:29 PM
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Years ago, I recall that they changed the code to require NO vapor barrier behind shower surrounds. Can't find the reference right now. The thinking was that it's a high moisture area, so you don't want to trap it one way or the other. No vapor barrier allows it to dry in either direction. That being said, kraft facing is a vapor retarder, not a vapor barrier, (they are not the same) so it's not the end of the world if you leave it. But you could pull it off.
 
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Old 11-21-19, 03:20 PM
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Good to know Xsleeper. I was thinking the RETARDER would trap the vapor between the kerdi board and the RETARDER too and that would be an issue. On the other hand, without the vapor RETARDER, I was worried about vapor getting into the fibreglass and causing mold. I'm just going to be lazy, leave it with the vapor RETARDER on, and move on with my life.
 
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Old 11-21-19, 03:46 PM
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Mostly wanted to change the insulation for a better sound barrier
From personal experience, R15 fiberglass, 3 1/2" will do almost nothing to deaden sound.

You have to get up to the R19, 6" thick insulation, to gain some minimal improvement.

If you want to improve sound absorption, get some soft touch (blue jean) insulation, that stuff works great!

Have heard Rock Wool is good, just have no personal experience!
 
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Old 11-21-19, 04:01 PM
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Dear Marq,

It appears in his photos that this is a double wall. (Shared wall) So he is likely putting 2 layers of R15 in. One half needs to slip behind the first wall. You would not use R19 in such a wall.
 
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Old 11-21-19, 04:07 PM
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And if not, then here is the idea to do so.
 
 

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