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Air and moisture barriers; a general question

Andrew_Sorensen | Posted in General Questions on

Other than convenience of construction is there any reason not to have the air / moisture barrier immediately behind the drywall? 

I realize air sealing around electrical and plumbing penetrations may require additional diligence but if the assembly meets or exceeds full wall and roof R-value for a given climate zone, and is vapor-open to the exterior, is such an assembly system workable?

If okay I would like to try a test build with inbaord sheathing with an inboard side liquid applied barrier. 

Do you have any thoughts or experience with this kind of system.
Thanks in advance.

 

 

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Replies

  1. Malcolm_Taylor | | #1

    Andrew,

    Many wall assemblies have no sheathing at all, and until fairly recently the primary air-barrier was usually either the interior wall finish, or a membrane directly behind it.

    1. Andrew_Sorensen | | #2

      Thanks Malcolm. My thought is whether it is still legit and workable from a modern building science perspective. If so, then I think cost effective yet high longevity structures could be produced this way.

      Balloon frame with steel (thermastrut); box out window and door opennings and sheath the inside of the framing; air barrier on the inside of the sheathing, then drywall; wiring and plumbing can be installed either early-on from inside or anytime later-on from outside; next install six inches or more of continuous exterior insulation (loose fill is likely sufficient) and then add roofing and rainscreen siding.

      That is the concept anyway. But as I am not a builder I am open to the likely possibility I am quite wrong. I thought I would try propose it anyway :-)

  2. freyr_design | | #3

    That assembly is going to be a pain from a rough in perspective.

    1. Andrew_Sorensen | | #4

      I'm not disagreeing because I have never done it but what do you see causing the most difficulty? Secondly, do you think it would be a pain even if the same trades people were to do it again after their first couple of times working it out?

      1. freyr_design | | #5

        The plywood, and yes.

        1. Andrew_Sorensen | | #6

          Okay, good. Thanks.

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