Is it okay to insulate my interior wall cavities with 1 inch blue insulation styrofoam and then r13 bat insulation on top of that before I sheetrock

  • You can, but the question is why. Common reason is sound deading, but not sure if that is best.
    – crip659
    Commented Apr 1 at 23:09
  • 2
    R13 bats are 3.5 inches thick. If you added 1 inch of Styrofoam, you would be compressing the bats and defeating some of the insulating properties and adding unnecessary cost.
    – RMDman
    Commented Apr 2 at 0:13
  • What is the purpose and what concerns do you refer to by "okay"?
    – jay613
    Commented Apr 2 at 6:24
  • Styrofoam has much lower vapor permeability than fiberglass so if you put it on the outside, in winter it will kind of act like a vapor barrier and you may get condensation. In summer it will prevent condensation from drying. Unless you live in a climate where you need lots of air conditioning, vapor barrier should go on the inside.
    – bobflux
    Commented Apr 2 at 7:04


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