Spray foam / air sealing sill plate in finished basement?
aberrant
| Posted in Energy Efficiency and Durability on
I’m finishing my basement in Boston and I have installed 1.5″ XPS (yes should have used EPS but it’s already been done!) rigid foam from the bottom to the top of the 10″ poured concrete foundation walls. The majority of the basement is above grade. I spray foamed the bottom of rigid panels to the slab but I haven’t yet spray foamed the top of the them. My house was built in the 60s and the sill plate is a 4×6 direclty on top of the foundation wall (with mortar to level it) and no capillary break.
I’m finishing in front of the rigid foam with 2×4 walls and Rockwool.
I’m debating a couple things:
- Do I spray foam the gap between the top of the rigid foam and top of the foundational wall or leave it open? My thinking here it would help dry the sill if there’s any moisture issues since the top of the foundation and the sill plate would be exposed and able to dry to the inside.
- Do I spray foam the entire area from the top of the rigid foam, top of foundation and the sill plate with something like FROTH PAK or other closed cell foam?
I’ve read conflicting things on here on whether or not to seal up this area especially where there isn’t a capillary break between the foundation and the sill plate.
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Replies
aberrant,
Unfortunately this is a situation where it's not possible to assess the risk of sealing the plates, because it varies so widely depending on individual circumstances. The vast majority do fine, some don't. Sorry - I know this is not very helpful advice.