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vapor barrier for retrofit device box (ie. new plug on finished external wall)

vapor barrier for retrofit device box (ie. new plug on finished external wall)

Old 01-23-13, 07:41 AM
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vapor barrier for retrofit device box (ie. new plug on finished external wall)

I am an electrician and often required to add a receptacle in a finished basement. It is my understanding that if a house is wrapped with house wrap during construction (eg. Tyrap) it acts as a vapor barrier. Consequently, if you install a plug on an outside wall on or above the first floor of the house you would not need to add a vapor barrier as long as you do not cut into the wall with the house wrap.

What about in the basement? Would you not need a vapor barrier? I would say yes unless it is insulated with foam. If you do need a vapor barrier, how can you effectively include a vapor barrier with the electrical device box in a finished basement so it forms an effective vapor barrier? This situation would also apply to older homes (eg over 15 - 20 years) in the entire house that do not have a house wrap.


AF, New Brunswick
Old 01-23-13, 03:25 PM
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House wrap is technically a weather resistive barrier, not a vapor barrier per se. It does not stop the flow of moisture in both directions like you would expect in a vapor barrier (6 mil plastic for instance).

Now, in a basement, you are talking about an interior wall, I presume. If not correct me. If you are retrofitting (old work box) a receptacle or switch and cut through the vapor barrier, you can use a good caulking around the perimeter of the box and the opening in the sheetrock to help seal it back up, but, if you check all the original receptacles and switches, the vapor barrier was cut around them anyway, so it would really be a moot point. It's not perfection, but what we have to work with. Incidentally, except for a walkout wall in a basement, there would be no house wrap, since it is only on the exterior walls exposed to the weather.
Old 01-23-13, 08:44 PM
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When I find vapor barrier behind drywall or housewrap behind siding, I try to cut the opening I need without damaging the vapor or air barrier, then cut that in an "X" pattern, install the box, and lap the fabric or plastic over the edge of the box. Can't always make it happen.

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