I had a building science company do a crawlspace air sealing retrofit to my 1960s cabin.  I was having significant air quality issues and was advised to seal off the crawlspace to reduce moisture and stack effect.

Since that install things have gotten worse - no air flow and high humidity and I am worried their installation approach could be casing more issues than it solves.   I have since put a interior dehumidifier in the space in the interim and that has helped a lot but there still is air communication between these spaces.

They sent me the attached rendering of their application.

It’s 3” eps foam board, 7 mil poly (with punctures due to a rough rat poured concrete floor) No poly over the foam and the rim joists where left as an open unsealed cavity behind the foam board.

Anything I have read suggests it’s critical to seal the rim joists which is what I thought I was paying for.  Because they are a building science company, they are suggesting that it’s not necessary and that if I am still experience airway issues at the interior floor junctions (which I am), that’s due to the exterior and not the crawlspace rim joists?

Not sure if this is the right place to post.  Seems very difficult to get a clear code defined approach that is documented and current.

I live in an Oceanside community with high west coast humidity year round.  It gets cold in winter but usually above frost temps most winter days.

Crawlspace Air Sealing - Is this the Correct Approach?