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Community and Q&A

Venting a House Roof Intersecting a Porch

Reed_D | Posted in General Questions on

What is the best way to ventilate my main roof, the bottom of which terminates under the porch roof? I’m adding exterior mineral wool insulation to the wall below, and though it won’t see any water, a ventilated rain screen with 1x battens to attach new siding. Can I simply leave a gap in the wall sheathing at the top, connect that to the rain screen cavity, and the main roof can draw in air that way? Or are there risks to this approach? I’m located in Minneapolis (climate zone 6a).


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  1. Expert Member


    I would not make the wall venting continuous with the roof for a few reasons.
    - It creates a continuous concealed space, bypassing fire-blocking, through which flames can spread.
    - The depth of rain-screens is not sufficient to get the required free-vented area.
    - Rain-screens are there to remove moist air. You don't want that air moving into your roof assembly.

    Just use spot vents on the wall of the porch.

    1. Reed_D | | #2

      Thanks Malcolm! Much appreciated

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