Insulating Rim Joists on 100 y/o balloon framed home
Long time lurker here. I have air leaks at my rim joist and planned on using rigid foam and spray foam to seal them up. Previous owner had put insulation batts in the space, and when I peeled a section up, I realized that my home is balloon framed. Now I’m not sure how to proceed, and if I even should. I am considering using Great Stuff and just sealing around the bottom of the rim joist and putting the batts back in place. The rim joist is about 2-3′ above ground so hopefully I won’t have moisture issues, as the joists appear to be in good shape and the insulation batts have probably been there a few years I’m betting. Everything I have read say to never use batts in this space, but maybe I can leave them since Its high above ground? Any advice on how I should proceed?
Thanks
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Replies
Go ahead and use can foam to seal both the band joist & foundation sill.
Even if it were a poured concrete foundation with only 15" of above grade exposure you won't run into moisture problems at the band joist or foundation sill unless you have very little roof overhang and/or lousy surface water management. If it's a fieldstone or rubble foundation the amount of capillary wicking would be quite a bit less. Brick foundations can go either way depending on the type of brick, but you're still going to be fine with that much outward drying exposure.
Thanks! Would it be a waste if I put rigid foam over the fiberglass insulation? In other words, the rigid foam will be on the interior side of the batts, sealing up the basement from air leakage up into the above floor.