vapor diffusion

Do I Need a Vapor Retarder?

Posted on January 31,2015 by user-756436 in perm

Every couple of weeks, someone sends me an e-mail with a description of a proposed wall assembly and an urgent question: “Do I need a vapor retarder?” Energy experts have been answering the same question, repeatedly, for at least thirty years. Of course, even though I sometimes sigh when I read this recurring question, it’s still a perfectly good question.

When Sunshine Drives Moisture Into Walls

Posted on January 31,2015 by user-756436 in diffusion

Builders have worried about wintertime vapor diffusion ever since 1938, when Tyler Stewart Rogers published an influential article on condensation in the Architectural Record. Rogers’ article, “Preventing Condensation in Insulated Structures,” included this advice: “A vapor barrier undoubtedly should be employed on the warm side of any insulation as the first step in minimizing condensation.”

Forget Vapor Diffusion — Stop the Air Leaks!

Posted on January 31,2015 by user-756436 in air barrier

Last week’s blog answered some common questions about vapor retarders. This elicited a comment from Bill Rose, research director of the Building Research Laboratory at the University of Illinois in Champaign. “We might imagine a future in which the building code sections that address the vapor barrier would all go blank,” Rose wrote.

Vapor Retarders and Vapor Barriers

Posted on January 31,2015 by user-756436 in polyethylene

Although building science has evolved rapidly over the last 40 years, one theme has remained constant: builders are still confused about vapor barriers. Any energy expert who fields questions from builders will tell you that, year after year, the same questions keep coming up: Does this wall need a vapor barrier? Will foam sheathing trap moisture in my wall? How do I convince my local building inspector that my walls don’t need interior poly?

Air Barrier or Vapor Barrier? - Building Science Podcast

Posted on January 31,2015 by JoeLstiburek in air barrier

_This podcast series is excerpted from a two-day class called "Building Science Fundamentals" taught by Dr. Joe Lstiburek and Dr. John Straube, of Building Science Corporation._

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