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Community and Q&A

How to Vent this Cathedral Ceiling

Curtis8907 | Posted in Energy Efficiency and Durability on

Hi, there.
I’m looking for someone to let me know if this particular venting detail for the roof of a build will work. For starters, I am located in Northern Ontario. The roof is a 4/12 shed roof with a 24 inch raised heel. I’d like to use dense pack cellulose to insulate. The roof detail is as follows.
-Trusses ordered with no over hang.
– Sheeted with 1/2 inch plywood.
– Continuous Membrane from Siga or Pro Clima. (Haven’t decided)
-Over hang screwed through the sheeting and strapping that covers the span of the roof and allows ventilation.
-Standing Seam metal roof.

My question is if the ventilation under the metal roof is enough to ventilate the cellulose insulation without using baffles. Take into consideration that the membrane will be vapor permeable.

Basically, will this work?

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  1. Steve Knapp CZ 3A Georgia | | #1


    I'll give your post a bump.

  2. Jon R | | #2

    IMO, anything less than 1.5" doesn't provide enough venting to protect cold sheathing. I assume that your code (something similar to IRC R806) covers the issue. Investigate support for the metal roofing and whether "above sheathing" vents are allowed.

    1. Curtis8907 | | #3

      I could use 2x4 strapping though?

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