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We had a water issue several years ago and the drywall had to be removed along with some insulation.

The replacement insulation that was put it did not have a moisture barrier nor any kind of facing on it. Do I need to remove the drywall and replace with the correct insulation? The wall in question gets direct sun from the morning to mid/late afternoon. It is probably a 4x6 area.

The only reason I thought of this is because I needed to research insulation for a uninsulated garage that needs to be insulated and saw that a moisture/vapor barrier is required.

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    We would need much more information to answer properly. Was there a vapor barrier to begin with? What climate are you in? What's the age of the home? Are you experiencing actual problems?
    – isherwood
    Commented Aug 5, 2021 at 18:12
  • You don't have to replace the insulation if you can add a barrier/retarder. Determine what side (in/out) the retarder of insulation elsewhere in the house is on, and just put the VB on the same side.
    – P2000
    Commented Aug 5, 2021 at 20:56
  • What do you have for sheathing in this wall assembly? Keep also in mind that the facing on insulation is a vapor retarder alone, not an air barrier, and the latter is much more critical than the former
    – ThreePhaseEel
    Commented Aug 5, 2021 at 23:49

2 Answers 2

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The vapor barrier should be on the living-space side of the wall. So you typically have:

  1. Drywall
  2. Vapor barrier
  3. Insulation and wall studs
  4. Sometimes "R-board" or similar foam core products are uses here.
  5. "Housewrap" type water barrier (i.e. "tyvek")
  6. Siding

If your drywall was replaced without vapor barrier the insulation will become soggy leading to poor insulation performance and eventually water damage.

Remove the drywall, place a vapor barrier and then re-installed the drywall.

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    "The vapor barrier should be on the living-space side of the wall." - Umm, vapor barrier placement is climate-specific.
    – MonkeyZeus
    Commented Aug 5, 2021 at 16:11
  • You'll have to be more specific as I have never seen it any other way.
    – jwh20
    Commented Aug 5, 2021 at 16:12
  • i.sstatic.net/EfyjB.png from certainteed.com/insulation/resources/do-i-need-vapor-barrier
    – MonkeyZeus
    Commented Aug 5, 2021 at 16:13
  • 4b: Sheathing (OSB, Plywood). Contributes to R value, like the drywall under nr 1. Also, If using low-permeability R board on the outside of the insulation, then there is no VP on the inside, so as to avoid trapping moisture.
    – P2000
    Commented Aug 5, 2021 at 17:43
  • Apologies if I wasn't clear in my OP. I understand the vapor barrier is on the inside. My question was that when the drywall got damaged, they removed the insulation as well and replaced it with insulation that was not faced. From @jwh20 answer it sounds like I need to remove the drywall and replace it with facing insulation.
    – amrog
    Commented Aug 5, 2021 at 22:05
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This simulation site offers free and precise information on moisture produced in dependence on inside/outside air parameters and wall layers:

www.ubakus.com

A simple first approach is to open a wall example and to edit the layers in order to match the given or plannified sequence.

In a few minutes it reveals problems with missing vapor barriers or the order of layers.

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