I have gutted an area for a new bathroom in an old wood house built in 1863. The only thing between the exterior and the inside of the bath is thin clap board siding. I will be putting unfaced insulation up and covering it with plastic facing the interior of the bath. The wind can blow in between the clap board so I want to cover them with tar paper first as protection. Is tar paper considered a vapor barrier? I know you are not supposed to have facing on both sides of insulation.
Also, how does one secure unfaced insulation to walls without tabs?