I live in Wyoming and our winters get down to -20. I am new to having chickens and was told to just keep my coop chicken door open for them and if they get cold they will go inside. My coop is well built and insulated. Pine shavings on the floor. 6 foot by 6 foot coop with 6 hens. If one of my northern chicken keepers would offer an opinion it would be appreciated. Thanks!