We are building a dental clinic in central texas. 2 x 4 walls, osb exterior with house wrap and brick exterior. We have always used fiberglass insulation with a vapor retarder. The insulation contracter we hired says they never use a vapor retarder because of moisture problems. I understand the vapor retarder will not affect r values, but am not sure if he is correct about not needing it.
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Which direction would the vapor barrier go if you used it?
Vapor barriers go toward the conditioned space as I understand.
"Vapor barriers go toward the conditioned space as I understand."NO!They go on the oposite side of the condensing surface.Depending on the time of the year and the climate that surface can vary.http://www.buildingscience.com/designsthatwork/hygro-thermal.htmhttp://www.buildingscience.com/designsthatwork/hothumid/default.htm
http://www.buildingscience.com/designsthatwork/mixedhumid/default.htm
Thanks Bill for making that distinction.. I have never built in the Southern climates. If I understand what I am reading, it would be better to have the vapor barrier on the outside..along with a air space behind the siding. Because of the almost constant AC, the inside of the walls outer surface is going to be cooler surface and therfore water condensation on the vapor babrier. In this case would it even be better to have no plastic then have it on the wrong side? thankshttp://www.thesmallbuildingcompany.com
Do yourself a favor an INSIST on cellulose insulation especially in the attic/ceiling. Put in more than code minimum.
You'll save a bunch of money on air conditioning costs.