Vapor Barrier Dilema

northernbuilder

I am a contractor visiting from Alaska to remodel my sisters cabin up the canyon. In Alaska we swear by a tight vapor barrier, yet I've been warned against it by a rep at the builders supply store. I am in an unfamiliar climate and wondering what the standard proceedure is for vapor barrier in a year round residence in a cold yet arid climate such as this. Any advice from the local pros?

Dustball

Where is "the canyon"?

Francois

It's all about location/climate. Check Joe Lstiburek's website, buildingscience.com, for the whole gamut of issues with vapor barriers and vapor retarders. But basically, unless you're in "extreme cold" regions, you just want a vapor retarder, not a vapor barrier.

northernbuilder

When I posted my chat I assumed this was a chat for Utah builders and now realize this is a larger forum. I am referring to Big Cottonwood Canyon outside of Salt Lake City,Utah. It is a cold climate (can reach 20 below zero) yet is rather arid. I am familiar with the dangers of trapping vapor in walls. The stud wall is 2x4 with fiberglass and T1-11 exterior. There is no house wrap. The lid is A-frame style and we are installing 5" of polyiso between timbers on 4' centers. Exterior of the polyiso is t&g,1" foam and intact steel roofing. Any advice?