I want to make a workshop/garage in a detached building. Currently the walls are simply concrete blocks with a metal isolated roof. Dimensions are about 16Wx25Lx8H. I'll mostly be using it during the winter where temperatures can get down to 0F. I'm planning on installing an electric or gas construction heater for when I'll be using it and plan on heating only when in use.
I want to put up walls of OBC boards. What would be a good way to improve isolation? Would foam boards between furring strips be sufficient? The other option would be 2x4 framing wall with Fiberglas insulation (with vapor barrier?).