Hi; That is an interesting barn. You have already done a lot for the purpose of helping the barn last another 50 years. If you are thinking "retreat" you do not need to insulate, insulation would never pay for itself. Without all of the information, it sounds like you should just do some basic maintance and occasionally camp in the barn.

Jim

The closer you look the more you see.
"Heavy timber framing is not a lost art" Fred Hodgson, 1909