keeping in mine I have not had chickens in 30 years and just getting some again, but here in NW Central NH where we often get temps below zero, sometimes 20 below zero in the winter and the winters are long my experiences back then was too large of a coop and you had chickens with lost toes and combs. My mom started her flock with a big coop (big to her was 4 sq ft per bird per books) and those first couple winters she had a lot of lost toes and combs from freezing (even with a heat lamp in there). She made her coop way smaller the next year (4X8 indoor part) and had 12-16 birds for the next several years and never lost another toe or comb Me personally I have never wintered a flock. I had mine spring/summer/fall and then they'd go stay elsewhere for the winter as my chicken housing was not good for winter Comments from other cold state people??? I will be building my coop soon and planned for a smaller than suggested sq ft size based on these experiences. My coop will be mobile. I can't let them free range here they would all be killed in a month just like most of my neighbors birds (one of them lost 28 birds in a month). Those who still have birds don't let them out unless they can sit right there and watch them. We have everything from tiny Short tailed Weasels up to Bears all in the yard almost every day and night and all sorts of species of "Death from above"