How do you keep your chickens warm in the winter

Where are you located, how are the chickens housed, free-range or run???

 

So long as your coop is dry and not drafty, there is nothing more you need to do. They have their beautiful down coats to keep them warm. It is all they need. Think about all the small birds like the junco, cardinal, chickadee, titmouse, etc. They don't have a nice, dry house, food and water supplied to them and they do just fine.