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Interior air barrier/vapor retarder

Shaun A | Posted in General Questions on

Quick run down. Climate zone 5A. Wall assembly: 2×6 studs, R23 rockwool, 7/16 zip, 3″ rockwool comfortboard, furring strips, siding. Question is do I need to use an interior vapor retarder other then my interior drywall? Should I use a product like Certainteed MemBrain as a secondary air barrier and vapor retarder? I am doing a blower door test hopefully this week and am shooting for 1ACH50 or better.  I have been doing a lot of research on here and when it comes to wall assemblies and vapor I still get confused but I am learning.

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Replies

  1. Eric Whetzel | | #1

    Shaun, we used almost the exact same wall assembly as yours.

    We chose to use Intello as a smart vapor retarder and as a secondary air barrier. The feedback I received from GBA suggested it wasn't necessary, although it is nice insurance. The MemBrain would obviously serve the same function.

    You can read about our wall assembly in detail here:

    https://kimchiandkraut.net/2020/01/22/completing-our-wall-assembly-self-build-passive-house/

    https://kimchiandkraut.net/2019/07/11/siding-1-of-2-continuous-insulation-with-a-rainscreen/

    1. Shaun A | | #2

      Thanks so much. Loved reading your articles! I agree with the added security of secondary air barrier so I believe I will go ahead and do it. Now just to find Intello or MemBrain in this crazy world we live in right now!

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