I am looking for advice/guidance, I am thinking of Sealing/Insulating my Crawlspace in Climate Zone 4 New York State. The home is 1960’s split level ranch. In the crawlspace I have a rat slab concrete floor, open core CMU walls (asphalt felt paper 2 courses down from the top – although difficult to confirm), and an untreated sole plate with no sill sealer nailed into the webs on the blocks. The humidity level is high over the summer and has led to some small amounts of mold growth on the some of the joist over the years, but the sill seems to be in good shape.
My plan was to treat the mold and add Boracare, remove the existing batt insulation in the floor above replace with continuous rigid insulation (xps to and R-10) on the walls and cover with ignition barrier, insulate the rim joist (probably more rigid foam and spray foam any gaps), put down a plastic liner over the concrete rate slab, and install a dehumidifier as specified in https://www.finehomebuilding.com/project-guides/insulation/creating-a-sealed-crawlspace.
My concerns are installing rigid XPS foam on the open core CMU wall (all details show a grouted block detail or a poured or cast concrete foundation wall – (https://nyserdacodetraining.com/resource_lib/build-better-guide.pdf pg 79 ) and insulating the rim joist would eliminate drying of the untreated sill. Any advice? And thank you in advance.