I tried starting last year not heating the coop after reading the cons of heating the coop (greater possibility of coop fires, losing toes and parts of combs to frostbite, being hard on their systems, etc.) I have been very happy with it. And after some horror stories I have read about barn and coop fires, I sleep better at night. They sort of go into a semi stupor, sort of sleepy; but they are eating a lot and drinking a lot, and so far they are healthy. I have 42 hens in a 96 square foot floor space coop, and I know that chickens need between 2 and 10 square feet per bird, so I am at the maximum right now. I also know that each chicken produces 10 watts of heat, so I am pretty close to a 500 watt lightbuld right now. When days get warmer, around 30 degrees or so, I open up everything to get it aired out, and sometimes they come out, but at first I had to literally carry some out because they did not know how to process this new white ground! Today I opened up the coop and dumped a big bag of leaves in, and of course, the chickens went ballistic! They flew out of the coop and landed in deeper snow, and just sat there and did not know what to do! I had to actually pick up my Salmon Faverolle and place her back in the coop--she was so perplexed and confused and did not know what to do--her feet were not engaging with any ground! We live in Minnesota, and I don't believe that it has gotten below 15 below yet, but it certainly seems so with the wind chill sometimes! So this is the second year I have not heated the coop, and no losses in the cold weather. On the contrary, I have lost many in the summer due to the heat, and none in the winter due to the cold!