This has probably been asked a hundred times but I cant find a satisfactory answer I live in Northern Michigan... by Traverse City, not in the Upper Peninsula but in the top West of the Northern Lower. I have a chicken coop that is 48 x48 on legs I will post a pic. I have 6 chickens... 4 Sumatras 6 months old now and two other chickens one little Old EnglishBantam rooster and one Bantam white cochin hen. Last year I only had the two bantams in the coop so I kept a light on them. I used verying wattages of bulbs through the winter. Ranging from 40 to 100 on our sub zero nights and days. I kept a thermometer and it appeard that by doing that my coop averages 45-50 all winter. It is insulated but not like a house. It is draft free. I have two doors for the front one with a screen and one solid if the wind is blowing and its nasty I would put the solid door on at night. The door is the door in the front that is small and they enter the coop through it. I keep it clean and keep Sweet PDZ ,Sawdust then Straw on the floor in the winter. What I am driving at is this.. some people say dont need to heat the coop if its draft free and I have grown chickens. But is that a rule of thumb for my location? I can see that if I lived in Southern Ohio there would be no need for heat. Right now its not an issue it appears that last night when it was 30 the coop was 45 or so inside. I am concerned with the days we have constant cold. I dont want a light this year. Last year we had plenty of room to hang a light and the two chickens could set on the perch just fine but this year our perch is full and there is no room for a light. I have seen those warmers that are safe for the wall or bottom has anyone used one of those? This is the coop. I cover the top of the cage with a tarp in winter and along the back it gets no west or north wind in winter.