I bought R30 unfaced insulation ( it was so cheap). I want to use it for my attic & the ceiling of my garage. How can i face the unfaced insulation? Can i use the paper for the roofing as a vapor barrier for the unfaced insulation?
Worry more about air sealing. I'd suggest you read on buildingscience.com and see if a vapor barrier (as opposed to a vapor retarder) is even recommended for your location (probably not, unless you are in an extreme climate).