Bricked-up AC portal, how to treat and seal?

beanmommaNovember 27, 2002

When we purchased our home 6 years ago we knew that there had been a built in AC unit in the living room wall. The previous owners removed the unit and bricked up the opening. They stuffed some insulation in the hole and nailed a thin wood panel over the inside. The wall was otherwise paneled.

On Monday I finally got tired of the paneling on the wall and ripped it down to the plaster. In the process I decided to remove the insulation in the hole and replace it with new, intending to patch the hole with drywall and seal it up permanently from the inside. I wanted to put new insulation in because the old appeared dirty and had evidence of mice.

While removing the insulation I discovered that a layer of canvas-textured vinyl/plastic was put between the insulation and the bricks. There was moisture and mold on the insulation and vinyl. I believe it is from condensation from the warm inside air contacting the cold surface of the vinyl. There appeared to be old water damage to the plaster wall, but I think it is probably from when the unit had been in the window. I have never detected leaking, moisture or a mildewy smell from this wall so I don't think it is a chronic rain related wetness that has caused the current mold on the vinyl.

I would like to remove the vinyl,clean out the hole then re-line, reseal, insulate and drywall it shut. It is a NNE wall...the outside being a bricked-up AC portal. Does anyone have any input into what sorts of barriers/liners I should use to avoid further condensation damage?

Thank you,


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Lynn, this is going to be a tricky one to do from the inside.

First, I think it is both a rain and condensation problem. I suspect that when the previous owners bricked over the hole, they simply stapled up a sheet of "vinyl/plastic". If they did not lap it properly any water that came through the brick (and water DOES go through brick) into the wall above would run down the wall, behind the plastic, and into the insulation. The reverse laps act like funnels to direct the water INTO the house instead of OUT.

You'll need to make sure none of your framing has been damaged by the water. If it has, you'll need to replace the damaged studs.

From the outside in: I would recommend using #30 felt being careful to tuck the top under the felt or housewrap above, so that it is lapped like roofing. You'll need to add some sheathing, like plywood over the hole on the outside face of the studs, then you can insulate and drywall. As you can imagine, you will need lots of extra hands to do this from the inside. The other option would be to take the brick down and do it from the outside. It would be far easier to do it that way.

    Bookmark   November 28, 2002 at 7:59AM
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