I live in Northern Wisconsin, where it gets unbelievably cold. Last winter it was -30 to -40 A LOT!!!!!!! But, first things first. Right now, its 18 degrees here. Is it too cold to open their door for them to go outside? Our coop is insulated well, and when I go in there it is surprisingly not too cold, but should we be adding any heat? We have one of the windows cracked slightly for ventilation, but also noticed the windows and door is really getting frosty. Do they mind not going outside??? I have a friend that has chickens and she said that she didn't open the chicken door unless it was at least 30 degrees. What do you all think????