That makes a lot of sense. The walls on 2 sides are cinder block, and the back wall is stone. Above that is metal roof on wood framing. I think the roof portions should be easy to insulate, and I'm guessing the cinderblock walls will need some kind of framing to hold insulation to. There are also windows on those walls, so I'll need to extend the window frame.
The hardest part (at least in my mind) is the barn doors. I'll need some kind of flexible flaps to overlap the doors, and perhaps the same for the inch or two they hang off the ground.
I'll look into designing in some kind of wood stove to my layout
PS - ideally I won't be covering the back (stone) wall in anything as I really like how it looks. May have to sacrifice efficiency for aesthetics there, but I'll take it!