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Looking at using black sheathing for air sealing /baffles cathedral roof

Geoff_Frood | Posted in Green Building Techniques on

I’m looking for a materiel to constuct some homemade baffles to provide an air gap for a dense packed cathedral roof. The trusses are 32″ inches tall with a 1/2 inch plywood deck on top. I understand the need for a gap to allow the deck to dry to the soffits. I’m looking for a material that is permeable enough to allow the cellulose to dry to the gap while providing an air barrier as well. I was looking at this
http://bpcan.com/en-CA/products/insulation-and-structural-boards/composite-insulation-panels/r4-hp-east-/
It claims to have a pereance of 30 but I’m a little concerned about its durability and I have no idea if it s suitable as an air barrier. Has anyone come across this situation and what solutions had you come up with.

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Replies

  1. user-1061844 | | #1

    Instead of putting up sheathing, which is heavy and you can use strips of ProClima Solitex Mento Plus.
    It is reinforced for dense pack insulation, very vapor open and waterproof. See this article how Alex Wilson used it to make a vented/waterproof chute above his blown in insulation. (Dislaimer: it is a product we import at http://www.foursevenfive.com, more details regarding this method here

  2. GBA Editor
    Martin Holladay | | #2

    Geoff,
    If you do a good job of air sealing your ceiling, then your cellulose won't get damp. (Damp insulation usually happens when ceilings are leaky. Leaky ceilings allow humid interior air to reach cold surfaces, causing condensation.)

    If the ceiling is airtight, the ventilation baffles don't have to be very vapor-permeable. People have successfully used thin plywood, stiff cardboard, or 1-inch-thick XPS or EPS for ventilation baffles. All of these products are vapor-permeable enough to work well.

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