Rainscreen – tie into soffit at top?
John P.| Posted inGreen Building Techniqueson
If there is an air path to the soffit, when creating a rainscreen assembly, is it sufficient to vent the top through the soffit, or does the siding need to have an opening all along it’s top edge as well?
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Replies
Both approaches have their advocates. The most convincing reason I've heard to avoid tying them together is that the air in the rainscreen gap can get heated by the sun on a south wall, and in the winter, that could contribute to ice dam problems if that air were brought into the attic.
That is reason enough to convince me not to!
John,
For a discussion of the question you have raised, seeAll About Rainscreens.
John,
It's well worth reading the article Martin linked to which is a comprehensive summary of everything you need to know. Just to flesh out the comments on rain screen venting: the cavity can not be continuous with the soffits in Canada (and similar thinking may apply in other codes) because it creates a concealed vertical space where fire can spread between the wall and roof assemblies. There are similar provisions for blocking the intersection between the two at interior soffits (or bulkheads) and holes in top plates for services. The idea being to slow the spread of a hidden fire moving undetected and unimpeded up into the roof system.
Martin - thanks! I missed that part about the soffits in that article.