My wonderful husband constructed a water heater using a chimney block with a paver over the top and a small flood lamp inside the chimney brick. It is warm enough to keep the water from freezing and also warms the brick to provide some warmth for them. Our coop is 8 feet long and 4 feet wide with ceilings of 6 feet. The waterer is closer to the nesting boxes to prevent eggs from freezing and we also have vents near ceiling for air exchange. Last year we used a heated dog bowl for our ducks and that was ok. Thought we shouldn't have open water in coop with chickens and our 2 ducks this year. It gets mighty cold here in Northern VT and we have lots of wind. Next on list is constructing an outdoor covered run for them to hunker down in this winter.