Rim joists in cold floor
afos82
| Posted in Green Building Techniques on
I am currently renovating and taking the opportunity to properly air seal and insulate the cold floor between my living room and exterior carport below. How important is it to add rigid foam to the rim joist of the cold floor? Martin’s details exclude it. I am currently planning to fill the joist space with mineral wool batts and use Zip R at the underside of the floor/ceiling of the carport. Do I need to add rigid foam here, or is the rockwool batts enough? Note, I am not adding rigid foam to the underside of the floor deck – just to the underside of the assembly.
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Replies
afos82,
Neither the foam under the sub-floor, or against the rim-joist is necessary in that section.
Thanks Malcom. I actually have quite the assembly. 2x10 joists (filled with rockwool) with a 10" dropped cavity and 2x4 subframing to support the carport ceiling. I'm planning to fill the 13.5" deep space beneath the joists with loose blown in cellulose. Including the zip R sheathing at the bottom, the assembly will have an absurd R value of +/-R65. Not necessary, but I'd rather fill the void rather than let air move around in it.