Shop insulation

[fredhargis]

There's little doubt in my mind that the Tyvek or an imitator would work as you want, if it put up with the proper fasteners (something with those plastic washers on them). The nice thing (maybe) about using Tyvek is you would be able to go back over it at a later date with some kind of sheet material like Homosote or even dry wall....at least I think you could. Those plastic washers might be in the way at that point. Actually, just staples might hold the Tyvek. It's really tough to tear, you could test it before installation.

[Turner52]

Why are the insulation companies telling you that? Did you tell them you would be heating it. Why would it be different than the ceiling in your home? I am sure the home has a vapor barrier on the ceiling. You said you would be using a faced insulation on the walls. That is a vapor barrier. Why on the walls? Check your building codes It will all be spelled out there. Unless the rules have changed since i retired 7 years ago you will need a vapor barrier on ceiling and walls to meet code. I would follow the code even though I doubt if you will be having any inspections. In Wisconsin you need Tyveck on the exterior of all homes and attached garages as well as detached garages that will be heated. Unheated detached you do not

[Dusty Workshop]

There is no Vapor barrier in a home ceiling here in Maryland either. It is typically unfaced insulation covered by drywall.

[Turner52]

Now I am curious as to why the codes differ from Maryland to Wisconsin? Maryland should be cold eneough that I would think they would be the same. I sure don't know but if anyone has an answer I would appreciate knowing, just to answer my cuirosity.Maybe differences in humidity? My answers were based only on my experience in Wisconsin. Apparently I shouldn't assume that things are the same in other states, Usually codes do have a good reason for being written the way thay are, but this baffles me. If anyone knows I would appreciate the knowledge. A learning experience.

[measure once cut remeasure]

Expensive, but wouldn't spray foam insulation in the roof joists work.  
The foam would negate the need for a moisture barrier, and no worry about anything falling down.

[tomsteve]

this is something a friend and myself thought too much on and should have went with our first thought which became the plan 24 by 36 garage shop:

put insulation baffles in(easier to do without a ceiling up). frame access hole. put 1/2" osb on ceiling. blow in insulation. ceiling done in about 8 hours. insulation blown in in about 2 hours. painted white in no time with an airless.

[Dusty Workshop]

As I mentioned before, I wish I had done spray foam before moving in but I didn't and I am not clearing out the shop to do it now.
I don't want to use osb or drywall because of the weight.
Unfaced Batts covered with tyvek seems to be the best option.
The unfaced Batts don't require a covering but I want one to keep the insulation from getting all over stuff and in my lungs.

[Stwood_]

Well. Check into the net covering that the blow-in guys use. Or go with the tyvek equivalent. Lots of look-a-likes for tyvek out there now.