Joist Rim Insulation
Good afternoon everyone,
Our cabin is located in Okanagan, British Columbia. Learning as we go as we’re no longer in touch with our builder. Been a super stressful build, but trying to move forward & get moved in before snow fall. Low slope ceiling that we had to have the builder come back and put ISO on the roof deck, now the interior ceiling is being batted. We followed recommendations from here – thank you!!!
We have now run in to rim insulation issue. Insulator wants to spray foam it all. Is there another option? We really want to avoid spray foam, if at all possible. If we ever do another build, we now know all the things to watch out for and have the builders do differently.
Please see photos.
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Replies
You can use exterior rigid foam over the rim joist. You can 'foam in' sections of rigid foam on the inside, then cover those with a mineral wool batt to provide fire resistance.
Aside from those two options, spray foam is probably the only other safe way to insulate this area.
Bill
Tlynn,
In this link Martin makes a distinction between insulating the rim-joists directly above your foundation, and those at a second floor which don't have the same risk of accumulating moisture. As the second floor ones are functionally quite similar to stud bays, I would insulate them in much the same way. Fill the space with batts, and cover with whatever interior membrane (poly, or a variable-perm one) you are using on the walls.
https://www.greenbuildingadvisor.com/article/insulating-rim-joists
Do you have a good exterior air barrier? Has the house been blower door tested?
If you have a good exterior air barrier and the blower door test is satisfactory, you could try to insulate these areas with spray damp applied cellulose.
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Thank you!! Appreciate all the input. We will have them batt & cover with membrane.