Foam board over faced insulation? (subfloor, install, bedroom, cost)
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We currently have R-13 faced insulation on our attic bedroom. The insulation is placed on the kneewall side with the faced closest the the drywall. After having an energy audit done, the advisor recommends that we install a 2 inch foam board over the existing insulation to increase R value and reduce draft. Will this scenario create a moisture problem?
In a word- No.
But before you go and buy sheets of foam-
Compare the cost of R19 batt to the foam board.
As far as the draft thing- it would require a lot of work, to actually get the board in there in such a way that it would stop drafts (most draft issues actually come from the bottom plate not sealed to the subfloor and penetrations through the wall i.e., receptacles).
Minimum code requirement for knee walls is R19.