Header block vapor barrier termination
FADLLC
| Posted in Green Building Techniques on
Is there a good detail or is it not worth worrying about how the vapor barrier terminates at a header block?
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Replies
FADLLC,
I'm assuming this is a shop. I wouldn't worry about it.
That was just a standard detail I grabbed just to have an image. We're in the south and the standard slab foundation down here, residential or otherwise, is a header block similar to what's shown.
I don't like it, for both energy and moisture reasons, but I only work in cold climates.
FADLLC,
Connecting the slab to the stem-walls causes two problems: You can't have a continuous vapour barrier, and you can't have continuous insulation. As Michael said, those are a lot more serious in colder climates than that the south. If it's the standard detail where you live it's probably fine, but perhaps not the type of high performance detail usually recommended on GBA.
I've drawn a bunch of floating slabs that aren't getting built, so I figured I'd make sure I wasn't missing some best practice on the vapor barrier with a slab to stem connection.
Best practice varies with location and site conditions, but I like using a concrete stem wall with a shelf at the top for vertical foam, and a slab thermally isolated from the stem wall.
So it sounds like the answer is move north or just let the contractor figure out how they want to deal with the vapor barrier.
FADLLC,
I'd say the choices are to use the same detail as everyone else, and put up with it being a fairly poor one, or pick one that works better but isn't commonly done where you are.