Lots of moisture Behind vapor barrier.


Old 06-30-15, 11:50 AM
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Join Date: Jun 2015
Posts: 1
Lots of moisture Behind vapor barrier.

Ok so here is what I am trying to figure out before I rip out my entire wall.

Cinder block home in FL built 1984.

A few years ago I did a bathroom renovation and when pulling down the drywall on one ext wall I found my installation was just socked. There was no sign of any leaking and the only thing I could come up with at the time was the ac unit sat on that wall any somehow was causing something to happen?? Anyway I replaced the bat with foam and re vapor berried it one and done.
So this past month i noticed water at my base board for my MBR. This is on the same exact wall as just down a little from the ac unit. My first thought was window leak. So i checked all that no issue. I then went back to my ac theory and diverted the fan away from the house. I then ran my dehumidifier. Which got a lot of water however there is still moisture in the insulation. The one this i noticed is the wall that has the foam board I put in does not look to have the problem anymore. Any thoughts other then to pull the wall down? Which still may happen based on mold. Howerver I want to make sure to fix the problem if it comes to that.
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Old 06-30-15, 02:01 PM
Join Date: Oct 2008
Location: New England
Posts: 9,990
You are fighting with moisture (humidity) in the air. In the hot south when a home is air conditioned the vapor barrier needs to be on the exterior of the fiberglass insulation. In your case as the moisture vapor moves through the wall it reaches the cool inside wall, be that drywall or a vapor barrier, and condenses giving you the moisture you see.

Where you installed the rigid insulation, although not perfect, it is still preventing the air flow that occurs within fiberglass insulation, thus limiting the moisture that reaches the inside.

Rebuilt the problem walls with the vapor barrier near the outside and air seal everything right down to the foundation or slab. Depending upon your wall thickness, you can do some in rigid foam and some in batt insulation. There are guidelines for that. Then, no vapor barrier on the inside.


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