Alright, from the last concern about vapor barriers in a steel building flooring assembly (Is a vapor retarder/barrier good or bad between floors?– GreenBuildingAdvisor)
I chose to insulate the 2 × 10 floor cavities, but chose against utilizing the vinyl vapor barrier. It appeared that the drywall ceiling will produce enough of a retarder, and I just became worried the vinyl would become more a liability than a benefit.
Now that I am installing this, I had a couple questions
1. As you can see in the picture, the “ends” of the floor are supported by bar joists and are open/unsealed. My plan was to install 1/2 ″ foam as a vapor retarder and air barrier at these end bar joists then fill with unbacked insulation. Any problem with this strategy?
2. My walls dry to the inside (constant XPS on beyond building), so the webbing space of the WALL trusses are being taped with Tescon Vana tape and a piece of 1 ″ closed cell backer rod in front of that (to still allow drying while supplying an air seal to the cavity).
I thought about doing this same treatment to the ceiling bar joists that have the same gap (see photo). Nevertheless, it appears the subfloor will enable adequate drying. Should I just leave the gap and let the trim cover/air seal, or should I pack with backer rod? Or, do I need to do the vapor perm tape/backer rod combination like I am doing for the walls?
Thanks