Back in the early 60's we used a reflector design on our moose hunts. We used trees and brush covered with a tarp (for shedding rain.) With a large fire heat will collect inside although I wouldn't want to be out in -20 weather. Trouble is at the end of a week you will come out reeking of smoke. Without finding a shower some where you probably will not be able to live with yourself long enough to drive home.
Jim
