I feel that not all sq feet are created equal. My coop allows only 5 sq ft /bird on very cold days and a run of about the same size on warmer days, however it is tall with extra roosting space, well ventilated and well bedded. There is always water and feed and it is not drafty. The birds are all the same age and were raised together. Some coops are only a couple of feet high and give the birds no chance to spread their wings, others have cracks for the wind to blow through so they have to huddle together on the roost to stay warm. I have been in coops that the ammonia will bring tears to your eyes. This first winter may prove me wrong but they were shut in for three days in a row of brutal weather and were only in the run for around 4 hours today and I see absolutely no issues. Tomorrow will be a little warmer and they may spend more time in the run. My lights are on a timer and come on around 2:30 AM and most of the eggs are laid before 7 AM sometimes we get a couple later in the day. Perhaps having 14 or 15 hours of light is good for their attitude I know some people get depressed this time of year when the days are short.