I went with Soy Lock Spray foam for my metal building and am very happy with the outcome. It is a closed cell foam and thus provides a moisture and vapor barrier. Not only is the bui8lding metal but I choose to use steel studs to frame in all of the rooms the only wood will be decorative. I also went with a fiber cement siding a bit of a pain to cut but again, living in a sub tropical environment termites of every variety are a major problem as is moisture, rot, rodents, and a whole variety of vermin. I've found the foam reasonably easy to remove where I needed to, scrapes of the metal and once the surface is broken a wire brush works amazing. I have chosen to do the spray in 2 stages, so that it was easier for the foam to cover the main structure then finishing the framing and siding plumbing, wiring etc and doing the second inch. All of the plastic caulking tubes that can't be recycled are driving me crazy though. I am going to split some and see if I can use them over the wires that are exposed to keep the foam from them, we shall see, but finding a way to reuse them is high on my list.
With only 1 inch of the foam and the building being mainly open it is already 3-5 deg nicer inside than out, be it warmer or cooler; Being my existing 'house' is only 10 deg different than the outside I'm amazed. Here most folks run their AC 8 months out of the year so being able to keep the inside temp under 80 will be a huge boon, getting close to closing the place up so we shall see.
Also I am crazy allergic to everything and so is my daughter, we have both been handling and working with the foam and in the building with no adverse reactions and that is also amazing since 10 min in any store is enough to make either of us feel ill, so once sprayed the foam is fairly MCS friendly.
We are looking forward to experimenting more with cob and other materials but it is a challenge here. There is NO rice, or pumice around the very southern Tip of Texas is an ancient alluvial plain from when the rivers actually flowed. Cotton, sorghum, cabbage, onions, melons and sugar cane the main crops since 'cheap labor' has sent broccoli and similar food farming south of the border. Most farmers spray heavily which sends their pests my way, at least the birds and butterflies also like my place

Sadly all my research has led me back to steel, and concrete for construction. I was shocked to find massive termite tunnels in some insulative foam panels I had been given that were on edge on a pallet, the termites ate right into them!?!