I've been sensitive to mold, chemicals and have had food sensitivities for 21 years now. Tried all kinds of avoidance tactics over the years this is my latest attempt at controlling my symptoms.
Below you can see ceiling rafters spaced on 24" centers which is important if you are going to be laying 4x8 foam panels like I did. The framing for the 5x6' windows are in place. The windows are facing south for passive solar heating. Which is wildly effective. The inside of the building averages 20 degrees warmer than outside without any supplemental heating. Unfortunately most windows are not designed for use on corrugated metal like the siding on the building and I had leaks. So anyone thinking of emulating what I did here would want to make sure the contractor addresses this problem. And why I made the interior walls removable so I could easily assess areas where mold could grow and rectify any problems in a timely manor. My solution was to take out the fiberglass batting and every time it rains I remove the panels and dry the area behind them. I haven't devised a long term solution. Really don't know how I'm going to do it. The contractor put in gutters which didn't seem to help but probably did somewhat. Hindsight I would have probably put an overhang in. Not just to direct the water from the roof away from the wall but to stop some of the rain from being blown up against it when conditions favor this.
I simply laid the 4x8 sheets of foam panels on top of the rafters. 2 layers 1", I overlapped the seams the best I could. Fiberglass batting probably not necessary but I had it left over from my old drywall building. So I used it.
This is what the ceiling looks like.
This is a view of how I insulated the outside of the metal panel wall.
I sheathed the outside of the inside wall and the ceiling with 4x8 sheets of foam panel after I installed the fiberglass batting. I than covered this with a single sheet of visqueen to hold everything in place and prevent heat loss through convection. Even transparent visqueen is opaque to infra red which makes it a radiant barrier also. Reading I have done says vapors from visqueen are not substantial under normal conditions. Not sure my use here is normal. But the seams are tight enough on the foam panels that they act as a pretty decent barrier to off gassing of the plastic sheeting. What I am saying is I accept no responsibility to anyone who adapts any of the building methods stated on this site. Also styrofoam is ordinary extremely flammable, I have tried burring these panels and they don't burn to well. Almost have to hold a flame to them to keep them going. So almost certainly most any kind of foam panels have flame retardants incorporated into them. As well as the fiberglass batting I used. (I assume) I did have to go back and remove the styrofoam clean behind it and put corrugated metal in their place because rat's got in under the bay doors to my building and into the wall. That upgrade is below as well.
How I insulated the interior walls
I bought this restaurant equipment (metal table) off of amazon.com. I couldn't find anything adequate to mount the sink on so I fabricated one out of metal drywall studs.
A view of my kitchen and dining room area.
My bedroom and den. I separated it from the kitchen and dining area with a steel stud wall sheathed with 4x8 foam panels. All the other inside partitions are built this way also. I did the same thing in the back where the bathroom is just behind the fridge.