Getting close to building a large and tall pole building for multi purpose.  CLimate controlled, foam under slab, radiant heat, etc.  Want to obtain good R values in walls and ceiling, which is proving tough to hit.  This will have 2x6s on edge throughout so I was planning to just use the opening to install 6" plastic backed glass in the walls, and the same in the ceiling but first use unfaced batts, then go over the ceiling again with 6" faced for a total of 12". 

One point I notice in buildings is they seem to leak a lot of air?  I was wondering about installing a wrap on the outside of the whole building before installing the sheeting?  I have concerns with a "double vapor barrier here" but wondering if leakage is likely high enough to be a non-issue?  I will not finish out the interior for yrs so the plastic backed batts would be it. 

I know LOTS of people try to just clamp batts under the sheeting but that kills the R values and I want a good building.  This would be close to an R40 ceiling and R19 walls?  Do I want more in the walls?  I have run calculations for heat gain/loss but cannot find much that directly considers the difference in ceiling and walls? 


Also, as help will be minimal, I need to develop fast ways to install!  I want to precut my batts, maybe even have them custom cut? Or, if not, what is a fast way to cut them? With 24", I found my paper cutter was the hot biz!  But that thing is 24" max.  I don't care about buying something if it speeds the process!

Another big point of consideration is how to band or retain the final layer bats in the ceiling?  My trusses are big girls on 12' centers! That is a long ways for a band system so I figured I needed something hanging off the purlins a bit for support?  Or, I am totally open to other ideas on the ceiling!

I was wondering about installing a wrap on the outside of the whole building before installing the sheeting?  I have concerns with a "double vapor barrier here"

You will get better air sealing from a wrap/sheathing combination (like Zip). Or taped foam.

The issue here is speed and cost. The building is sheeted with corrugated steel, not wood. There will be the air/vapor seal on the inside of the fiberglass but I have learned that their are never perfect and leak. So I would like to add an air seal on the outside as well. The Tyvek products seem to fit the bill BUT the cost is very high considering what it is! I am also not sure if these products already have an adhesive edge? I can see this being a real paint spanning this over framing but something needs to be there!

Housewrap is too expensive to use as an air barrier? (It's the CHEAPEST sort of air-barrier in my book!)

Where is this building located (by US DOE climate zone), and is it a house, a shop building or... ??