So, I'm ready to start investigating where to seal the duct work before insulating. Just for reference, this house is only six years old. One obvious place to address is the joints between sections. But, are the long seams where the rectangular trunks or round branches are assembled suspect as well? This is the end of the duct in my attic -- [url]http://i1218.photobucket.com/albums/dd405/Yukon_Youngun/EndBoxDuct.jpg[/url]. I'll be pulling up the batts around it to check the joints. I haven't yet tried to lift it, but should I try to put some foam board or something under it? There is only the floor, some fg batts and lots of air space in those joists (garage ceiling below). The other end of that trunk, where it comes up from the basement, is uninsulated for about 6-8 feet. Once I get that all sealed, good enough to just rewrap it in the fg?

I'm converting my detached 20'x23' garage into a studio apartment (with permits for everything). It was built in the 1930's. My contractor is suggesting that we put a 6mil vapor barrier on the old 4" concrete slab, followed by 2x6's on-edge, then fill the cavities with R-21 kraft covered insulation batts and then plywood subfloor over that. The local city inspector says this will be fine. Also, the footprint of the building is being extended about 2 feet beyond the old concrete slab (in other words, the wall where the original garage door was is going to be 2' further out). He has poured a new foundation wall at that point but he wants to just leave the interior floor area with dirt and put 6 mil plastic over that section before installing his floor joists. Does all this sound correct? I'm concerned that moisture will migrate up from the concrete (and dirt in that one area) and stay inside the floor joists, getting the batts wet over time.