We chose to insulate, not as much to keep warm in the winter, but to keep cool in the summer. So far, I am SO glad we did this. It has been ridiculously hot the past few weeks, and the coop is wonderfully ventilated and stays at a very nice temp. You can also see, we are adding electrical wiring for later use. We are going to eventually add a solar panel- just for light, and maybe a method of heating their waterer (I have read about using a light bulb inside a cinder block and setting water container on top- but that is something for us to learn this winter!).