I have three Rhode Island Reds which produce plenty of eggs for my husband and I. I had a coop built for them (around 6' by 8') in a corner of an old shed we have and they have three nesting boxes, 2 perches, and areas for food and water, as well as a nice large window. I also had a nice large outdoor pen build for them, approx. 12' long and 6' wide and they have two branch perches out there, a dirt bath and another waterer and feeder. I would love for them to be free-range but I fear the neighbors would not take kindly to them doing so, hence the big pen. The pen is fenced in of course and has a slanted metal roof. For the cold weather (we live in PA), I had the pen "wrapped" in greenhouse film, which keeps the pen dry, the drafts out, and lets plenty of light in. For being the "dead of winter", my girls are still producing an average of 2 eggs a day (one day last week I got FOUR!!!). On a sunny day, there is the "greenhouse effect" which warms up the pen nicely. There is ventilation inside the shed and in the pen (a slight gap between the building and the frame of the pen). There is straw in the coop and in the pen and I clean up droppings daily. I do have a heated base for the inside water fount. Often the pen gets warmer than the coop and I have been leaving the coop door open to harvest some of the pen's warmth. The girls seem to like the door open. However, next week they are forecasting temps in the single digits. I am wondering if I should close the coop door or not. My one thought is if I do, perhaps a little heat will be generated by the fount heater. But I kind of doubt it would make that much of a difference since the pen is wrapped in greenhouse film and thus drafts are prevented, Any inpit would be appreciated. These are my first chickens and I adore them!