OK to have kraft paper between vapor barrier and subfloor?
I’m renovating a room that has a raised floor over a concrete slab. The slab has a 10mil vapor barrier over it (in my testing I didn’t notice any moisture coming up through the slab). I’m trying to choose which insulation to use between the floor joists. With FG batts or rolls, everything at the store has kraft paper attached except for the thicker attic insulation which is too thick. If I have kraft paper underneath my subfloor, will it trap moisture between the paper and the vapor barrier? I guess I can pull the kraft paper off, if needed, but didn’t know if that was a lot of work or will damage the insulation. Other option is Rockwool, it just increases the price. Thanks!
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Kraft paper is a sort of old school smart vapor retarder, it's not a vapor barrier, so it isn't a risk for trapping moisture. You may find mineral wool easier to install since it's a little stiffer and will stay in place better than fiberglass, but there is no reason to be concerned with a kraft facer on the fiberglass batts.
Perfect, thanks Bill! Might spend a little more on the mineral wool for easier insulation once I calculate what the actual difference is (hard to tell from the shelf prices since they all have different coverages)
The easiest way to compare costs is to work out the cost per square foot for all the options and compare things using those cost/sqft numbers. That gets you apples to apples comparisons. Many times packages of batts will tell you how much they cover in square feet, but it's easy to calculate from the dimensions of the batts if they don't do it for you.