Our coop is small and well insulated and has no electric. The bedding is 4 - 6" thick of wood chips and droppings. They have access to the out doors all winter long during the day, and closed up at night. Their water usually gets a good crust of ice, but that is changed twice a day. The rooster had minor frost bit on the very tips of his comb last winter. We'll see how they do this winter.