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Conditioning attic in zone 5

rvitelli4 | Posted in Building Code Questions on

I’m in a Climate Zone 5 cape cod house with no soffit vents but theres a gable vent on both sides of house. Right now the attic is a conditioned spaced with kneewalls and some batt insulation extending from the first floor between the joists. I think I would like to insulate as an unvented cathedral attic, but don’t need to replace the roof yet. Is there any options for an unvented condtioned attic as an intermediary step for a few years until I can get some exterior foam board on the roof?


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  1. Expert Member
    Peter Yost | | #1

    Sure thing:

    See this GBA blog:

    And in the latest IRC codes (2015 and 2018) this is covered in Section R806.5.

    And to get the ratio right for air-impermable and air-permeable insulation by climate zone, see attached resources from SPFA.


    1. rvitelli4 | | #2


      Thanks you for your response. So there is no potential problems with using say close-cell foam spray under the roof for now and then going with foam board on top in the future?


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