Sealing gap between double BCI

This one isn't news you can act on — it's a homeowner posting a question on an online building forum, asking for advice about a tricky spot in his own crawlspace or basement rim joist work. He'd been sealing air leaks around the rim joist (the band of framing that sits on top of the foundation wall, where a house loses a lot of heat if it's not sealed) and ran into a gap between two joists that he can't reach. His plan was to drill holes and blindly fill the gap with spray foam, hoping that seals the hidden space, and he asked whether that's a good idea or if it's better left alone.

No one had answered the question yet at the time of posting, so there's no expert guidance to pass along and no rule of thumb to apply to your own house. If you're doing similar air-sealing work and hit a gap you can't see or reach, this is the kind of judgment call worth checking with whoever is helping you with the project, since blindly foaming a closed cavity can sometimes trap moisture instead of just blocking air.

There's no program, rebate, or deadline tied to this story — it's simply one homeowner's DIY question about a construction detail, not a policy or funding update.