Is roxul or un-sealed XPS alone sufficient for rim joist insulation?
I’m insulating the rim joists in my basement, and am about 2/3 done. I’ve used 2″ XPS, sealed around the edges with Great Stuff; a batt of Roxul over that for added R and fire protection; and a sheet of breathable fabric stapled over that to help keep the roxul in place.
The remaining 1/3 of my rim joist is very hard to get to. A couple of air ducts run along the top course of cinderblock, and even where that’s not the case the space between the first floor joist and the cinder block is only about 2″ (the space I have to reach through to do stuff).
Would just roxul, and/or XPS friction fitted and inserted against the rim joist — without the foam sealant — be adequate to increase the R without causing moisture issues? I can’t see how I will reach in there with sufficient accuracy to reliably seal all the seams with a foam gun.
Other alternatives or suggestions?
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