I live in Boulder, CO and have a young flock of Easter Eggers, Silkies, a Buff Orpington, Australorp and Brahma. This is my first post. Me and three other neighbors collectively own the flock and contribute to their care and cost. So far it has been wonderful. I'm trying to figure out what to do about the winter, the girls have a great coop and covered run. I read that the coop should be ventilated but not drafty. Can someone please elaborate on this? What exactly does that mean? I have a small exhaust fan (solar powered) and there are windows, but one of the members of my co-op thinks we should seal up the coop with caulk and insulation so we can keep them warm when they need it most (the temperature can drop into the single digits on occasion) and crack the windows when it isn't as cold. Is it worth the effort or even a good idea? How cold does it have to be to worry about them being warm enough? I can provide a light for heat. They will be fully grown by the time winter comes. I know that chickens suffer from respiratory issues if the air isn't fresh. Does this apply to even very cold days? I see many coops that have huge gaps and open areas in them. Thank you, Vivienne A Boulder, quasi-communal, modern hippie.