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Community and Q&A

Wall Assembly Zone 6 – Portland, ME

brad17 | Posted in General Questions on

Hey everyone, would welcome some feedback on this proposed wall assembly in Portand, ME!

Because our continuous exterior insulation falls below the recommended R11.25 to avoid wet walls (for budgetary reasons), we are hoping that this design will have ample drying capacity in both directions and so will perform well without concern for thicker ci. Do you think I am achieving that here?

sheet rock
intello plus w/furring
2×6 with R23 Rockwool Batt
Taped Zip Sheathing
1.5″ R6 Rockwool Comfortboard 80 ci
vertical nailers
unfinished cedar clapboard siding 

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  1. Expert Member
    Michael Maines | | #1

    Hi Brad, I think you'll be fine--the sheathing will be warmer and dryer than it would be without exterior insulation, and Comfortboard does not block drying ability. If you wanted a bit more resilience you could use CDX or board sheathing instead of Zip, but I wouldn't worry about it in this case.

  2. brad17 | | #2

    Thanks, Michael! I appreciate it.

  3. kyle_r | | #3

    Just curious, is 1 1/2” comfortboard plus Intello less expensive than 2” of polyiso without Intello?

    1. Expert Member
      Michael Maines | | #5

      I would say that 1 1/2" Comfortboard plus Intello is a more durable and resilient assembly than 2" polyiso without a vapor retarder. But a more expensive assembly.

  4. brad17 | | #4

    Great question Kyle. There are a few other factors in the decision, one of which is to avoid foam products if possible. We like the noncombustible nature of mineral wool. Also, the thicker the ci gets, the more challenging it becomes to apply siding and window trim.

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