Vapor barrier question


Old 07-27-10, 06:45 PM
Thread Starter
Join Date: Oct 2007
Location: MO
Posts: 18
Vapor barrier question

I'm going to be building another house in the future. The last house that I built, we used normal batts. I would like to use spray in fiberglass with water based adhesive in the future house. Of course, there will not be a vapor barrier if I use spray in fiberglass. I have seen a lot of info about using 4 or 6 mil plastic over the fiberglass insulation and then covering with drywall.

I live in southern MO so we have about equal amounts of cooling months as we have heating months.

So, is using 6 mil plastic with taped seams worth using in the area that I live in? I know it's used heavily up in northern areas but what about more southern climates? We can get cold weather as low as 0 degrees F but never for long. Usually no more than a week or so. We can also get 60s in the winter.

So, if we use spray in fiberglass, should we use the plastic vapor barrier or not?

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Old 07-27-10, 07:04 PM
Join Date: Oct 2008
Location: New England
Posts: 9,990
The primary transport of moisture is along with air leakage, so building new allows you to seal everything well and omit the vapor barrier. Especially in mixed climates, allowing the building to breathe is good. Plywood, sheetrock are good air barriers as long as they are sealed. There is a lot of information out there on how to build a super efficient home and starting new is absolutely the time to do it.


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