Here in Wisconsin, we are supposed to have sub-zero temps all week. When I winterized my coop I covered the ventilation holes with boards. However, I wanted to make sure the girls would be ok with the cold and when I checked. I cold see light around the boards. I am worried about drafts. I cut up a food bag and stuck it in the holes, but I am still concerned. I could see my breath in the coop. Is there anything else I can do for them?