Now that summer is winding down here I was thinking about the cold winters that will be coming too soon. How do I keep the chickens warm? Should I put in a heater or would a light bulb work just as well? Or should I let them get used to the cold and let them stay warm with their own body heat. Coop is insulated but not airtight. I haven't put vents in yet but was planning to do this very soon. If I use a light bulb, how many watts would be enough and how high should I hang it? I don't want to use a heat lamp if I don't need it.