Total Rebuild of a 1979 Dodge Class C

oldtrucker63 wrote:
I think this plastic is about 6 mil also, I have been overlapping the ends and same at the top where the wall meets the ceiling, I think this will seal everything air tight, I never thought of using Acoustic sealant to seal them I wished I would have though but its to late for that, For the most part, I can still seal it at the floor and I will do that, I'm just trying to get everything air tight.

I'm not sure if you want it all air tight. One thing I haven't seen mentioned when talking about insulation and vapor barrier in houses is that ceilings always use non-faced insulation. You want excess moisture and humidity to exit the structure (this is also partly why attics are vented at the soffits and up high). Your roof ia already a sealed membrane, so you might be best off if you end your vabor barrier six or eight inches from the top of the walls, intentionally allowing a place for vapor to exit. I can't say for certain, but suggest you do more research before sealing it all too tight. I'd hate to see you end up with unwanted water condensation inside after you're all done.