Comment on a rainscreen detail
GBA Editor
| Posted in Building Code Questions on
This is more a comment than a question. Looking at the detail for exterior foam with rainscreen siding, I notice strapping that vents into the attic space. This is something that is not standard here in British Columbia, as it creates a direct route for fire to move into the attic.
We usually vent the rainscreen gap at the top of wall prior to the soffit.
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Replies
Hi Ken -
We actually have wall details that vent both ways on GBA. But you are right, backventing of claddings is a big deal in many places. We should show or at least include text about what to do in urban-wildfire interface areas. We generally defer to Steve Quarles in this arena; see this presentation where he and Anton Ten Wolde have a stimulating exchange of slides regarding the "competition" between venting for moisture management versus fire protection details - http://www.forestprod.org/durability04quarles.pdf.
A balance can be achieved to some degree if vents are heavily screened enough to keep out embers and some new products are coated with intumescent paint so that they will close off the venting in the event of wildfire.