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Community and Q&A

Cathedral ceiling abutting hot roof

Tauntaun_Guts | Posted in Green Building Techniques on

I am designing a rectangular living/dining area where half the area has a cathedral ceiling and 8″ of external foam, and the other half has roof trusses with loose pack cellulose over a flat ceiling. The nailing surface of the foam is coplanar with the roof deck of the truss roof. Over this I plan on installing a standing seam metal roof. Will I have heat transfer problems from one roof system to the other?

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  1. GBA Editor
    Martin Holladay | | #1

    Q. "Will I have heat transfer problems from one roof system to the other?"

    A. Not if you know what you're doing. Every house needs an insulation layer that is continuous. Adjacent to this insulation layer, you need an air barrier. You don't want any air barrier discontinuities; nor do you want any insulation discontinuities.

    Between the horizontal ceiling and the sloped ceiling, you will obviously have a wall (one side of your attic) that needs to be insulated. Make sure that the insulation in this wall has no gaps -- especially where the wall joins the horizontal ceiling at the bottom and where the wall joins the sloped ceiling at the top.

    So: No gaps in your insulation, and no gaps in your air barrier -- and everything will be fine.

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