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Community and Q&A

Rainscreen venting connected to cold roof/back vented channel

Irishjake | Posted in General Questions on

Thoughts on connecting the vertical rainscreen vent channel to the cold roof/back venting channel on the roof or separating them.

I saw this last winter where the two channels are connected:
The solar washing of the siding caused subsequent ice damming even on a cold roof, due to the warmer air that comes from behind the siding was escaping up, under and out the roof peak. Anyone else encounter this?

Have you seen details that could eliminate this, but still provide an easy pathway for the vented air to escape?

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Replies

  1. Expert Member
    MALCOLM TAYLOR | | #1

    Brad, Our code specifically prohibits the rain screen wall cavity from being connected to the roof. If is seen as a concealed space for fire purposes, providing a path for flames to spread between the assemblies.

  2. GBA Editor
    Martin Holladay | | #2

    Brad,
    Here is the detail you are looking for (see below).

    For more information on this topic, see All About Rainscreens.

    .

  3. Irishjake | | #3

    Yes, I'm aware of that detail. But if you don't have soffit returns or don't want the soffit vent in the middle or outer edge of the eave/soffit, then you need to vent it back at the Frieze or bed moulding. This is the circumstance that I describe in my post, but was considering continuing my vent space right up and over the insulation from the bottom of the rainscreen all the way to the peak....

    Malcolm - In my case the wall rainscreen and roof "cold roof vent" are outboard of the insulation, sheathing and structural members and in the same "plane". I think this is different than what the code eludes to.

  4. Expert Member
    MALCOLM TAYLOR | | #4

    Brad,
    I'm in BC so of course your code probably differs, but no, the cavity of a rain screen is considered to be a concealed space. Concealed spaces have to terminate in a fire stop at the top of the wall, regardless of what plane they are in, and can not be continuous with the roof space.

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