All the advice I've found so far mentions square feet per chicken for the coop. Once mine are grown (German Bielefelders) I believe they will need minimum 40 square feet for 9 hens and 1 roo inside the coop. For warmth I would think that cubic feet per chicken would come into play however. Is there some rule of thumb for this? We are converting a horse stall in the barn for the coop. We are planning on doing a drop ceiling since the stall is open at the 3 of the top edges to the rest of the barn. The stall is 11 x 11 and the plan is to put the ceiling at around 7 feet so total cubic feet of 847. Our weather is mostly mild compared with some parts of the country, generally never getting below 25-30 degrees at night, but usually more in the 40's on average during the winter. Daytime is usually no lower than 50's on average. We were not planning on any supplemental heating so is that area too big for the chickens to stay warm?