I dont think I can build anything air tight.. but I have never really understood "needs to be well ventilated, BUT not drafty" And I have heard that since my life began, as I have been around horses forever. So. I have a metal shed. It is up. We are going to be cutting out windows and a door for the girls. During the nice weather they will be out in the run, with access into the coop unless I am cleaning it. In the winter, the plan is to have plexi glass sheets to put over the windows to keep the snow/cold out. The coop/shed will be insulated with the foam board insulation. Should I also cut some space out at the front(over the doors) and back(to match) for ventilation? And leave those open? Just maybe rivet some metal up there to block the snow, but still allow for air flow?