First year keeping chickens and I need some advice, please. I live in the NW suburbs of Chicago. It is beginning to get cold, especially at night. Do I leave any windows open for ventilation at night? Will they be too cold? My coop is a modified garden shed. I have installed a ridge vent for ventilation. I have two small windows. I do not plan on heating the coop at all. I would appreciate any advice. I love my birds and want them to be safe and happy. Thank you.