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Partially Vapor-Open Exterior Wall

Boerenkar | Posted in General Questions on

Hi all,

My tiny house has some DPC foil under the roof that hangs 20cm down the wall. Below is some UV proof, vapor open foil.
I could cut the DPC foil back and put additional vapor open foil under it, but that would require twice the amount of adhesive and extra work.

I’m now wondering if it would be bad to have a vapor barrier at the top of the wall, considering it’s only about 5-8% of the total surface.

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  1. Expert Member
    Michael Maines | | #1

    What is your insulation? What climate zone? What interior vapor control?

    1. Boerenkar | | #2

      From interior to exterior: 2cm wood, vapor barrier, 3cm PIR, 10cm rockwool, 0.9cm sheathing, foil, cladding.

      I'm from the Netherlands, in wintertime, temperatures usually range from -5 to 5°C

      1. Expert Member
        Michael Maines | | #3

        I think you'll have very little water vapor getting through that assembly, and if a section did accumulate some moisture it would likely be in the Rockwool layer, where it can move to a location where it can dry to the exterior. Without knowing more, it sounds to me like you should be ok with your current assembly.

        1. Boerenkar | | #4

          Thanks a lot for the advice! I'll go this way with the build I think :)

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