I built my coop this summer. As I have never had chickens before, I tried to take everything into consideration. The whole coop has inner and outer sheathing with 1 1/2" insulation throughout. The windows are triple pane. I have two deep red heat lamps at 250 watts each controlled by a thermostat set at 35 degrees. The coop is designed to be able to maintain 55 degrees at a -20 degree outdoor air temp. A 40 watt light is there for light and is on a timer in series with a photo-cell overide. That means if there is enough outdoor light, the electric bulb won't come on. I built the coop on a trailer for easy mobility. In the deep winter, I should be able to keep the chicken door open so the girls can go outside if they want and still maintain above freezing temps inside the coop. Here's a few pictures.