My hens are living in one of thesehttp://www.motherearthnews.com/DIY/2007-04-01/Portable-Chicken-Mini-coop-Plan.aspx So far we've been happy with it, but now it's getting cold and I'm trying to figure out the best way to keep them warm this winter. I was thinking about putting a hoophouse over it, but it looks like that's going to be too expensive. Another possibility is to stack straw bales along the north side and cover the rest with clear plastic. Maybe put some plastic bottles, full of water and painted black, inside to absorb heat from the sun. Dh suggested a hot rock like you would use in a reptile enclosure. A light bulb is not an option because it would be a major fire hazard in such a small space. I'm just not sure if 2 bantams are going to be able to generate enough body heat to go without supplemental heat all winter. They are already spending a lot of time in the doghouse portion of the coop, so I think they're cold, and it's only early November. I could put the whole thing in the barn, but then they'd get no natural light at all. Any suggestions?