i have seen insulation stapled different ways to the wall studs. i have seen face stapling and then i have seen the the vaper barrier folded outward and stapled inside the wall stud. which one of these ways are better or does it really matter?
If your of the school of thought that the staple and paper will make the sheetrock have a bump in it, then folding in is the only way to go, I've also heard a few (very few) people say that laying the vapor barrier over the stud and stapling both sides at once, it: 1) saves staples (and I say big deal...they're 10,000 for $3, but anyway) and 2) "completes the vapor barrier system by covering that extra 1 1/2 inches" (as if any measurable amount of moisture would get through the studs anyway). I personally don't think it makes any difference really.