I too have a open air dog pen connected to two small coops. Chickens love the open pen and have recently moved outside in it for their night time sleep. It has a roost so they are happy. We have a large tarp over the top and upper sides with the bottom half of the walls open. We recently had 28 degrees overnight so I had to add some panels to the bottom half of the pen along with a couple panels made from clear plastic so they could see out. I plan to make the bottom panels movable so I can roll them up out of the way when the nights are 50 or above. They don't like being so warm. I don't plan to use lights to lengthen their laying time. (I am going to let Mother Nature control the egg production during the short days of winter.) I will check their water, change it out if it freezes. I added oatmeal, sunflower seeds to their diet during the several days of really cold weather. They were fine. They seems to enjoy being cooler for a while. Here in SC our winter time can be kind of unpredictable, so have to be prepared for quick weather changes (called cold fronts here).