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Knee wall and cathedral ceiling insulation

711530 | Posted in General Questions on

Hi all

I have taken up the task of air sealing and adding insulation to the attic with the goal of increasing the attic insulation to r60 with blown in cellulose.  

I came across a knee wall and exposed cathedral ceiling where a room with a cathedral ceiling meets the rest of the attic.  The insulation on the knee wall pretty much fell off with time and the room is very hot in the summer and cold in the winter. 

I came across some cheap polyiso rigid insulation and decided to place it over the knee wall and exposed cathedral ceiling to air seal and hold up existing fiberglass insulation.  I have much of the work done and I just thought of airflow and am unsure if it will be a problem.

Is this approach ok, or will the polyiso over the cathedral ceiling be an issue?  Pictures are attached.


Michigan, climate zone 5

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  1. 711530 | | #1

    To elaborate more... The cathedral ceiling that runs into the attic has soffit vents and a ridge vent. Is isolating the ceiling and walls from the unconditioned attic a reasonable approach, or is there a better way to go about this?

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