So here in Southern California it's starting to cool off at night and here in HB the lows are dropping down to the high 40's (48ish?) and I'm struggling with closing the door to the coop. They are in an enclosed run and go inside by themselves when it gets dark and I have left it open for ventilation so far but I don't want them to get cold. I know some of you have chickens outside in colder temps than this but do you think I need to close the door and just have a small window for ventilation? Or leave it open because the fresh air is more important? How cold is cold for chickens?