Vapor Barrier / Insulating Below Grade
I'm a little confused about vapor barrier. I'm getting mixed information from contractors and other web-info and the thought of putting up a plastic sheeting directly against the masonry and then framing walls is.....well....scary. Any moisture collected has to go somewhere, so even if i don't see the problems within the finished space, where's it going/what's it doing behind that plastic sheeting? Something about that is disconcerting.
Framing walls with 2x4 and the interior walls would be insullated with R-13 batts (unless i hear differently). My question is how best to insulate the exterior walls. I like the idea of simply framing my walls with a 2" space between the studs and masonry and i'll finish the interior with drywall. But, is leaving that airspace enough to help avoid moisture build up? Here's what i think i need to consider
1) XPS against masonry, framed wall against that with NO batt insulation in studs
2) XPS against masonry, framed wall against that WITH batt insulation
3) XPS against masonry, framed wall with ROXUL (product my lumber store recommends for basements)
4) No XPS on masonry, 2" airspace with 2x4 walls and ROXUL or batt insulation in framed wall (not touching concrete)
Feedback is welcome,