Another question about building this double wall: "follow the double wall rules of open middle double insulation. a room in a room." When I frame around the garage door, do I need to wrap the frame around the garage door and mate it to the existing front wall, or can I simply frame up from side wall to side wall and from floor to ceiling, then fill with R19 batts and drywall the side facing inside the room? After that, I can always frame up another insulated wall a couple of inches away towards the inside of the room to complete the "open middle double insulation." Thanks again, Ben