We are newbies to keeping chickens. We have seven Heavy Breed poults, almost 20 weeks old. We designed our coop with the "old time" design of having the doors at one end open air, built with hardware cloth(wire mesh). We live in New Hampshire, and I'm wondering if we should use plexiglass to cover the "open air" door in the winter, and if so...what about venelation? We would be devastated if anything should happen to any of our girls! But the "open air " theory really makes sense to us also. I have read so many conflicting theories on the matter!