When I had chickens in Mountainair (6500 feet) we didn't put a heat lamp on them and they did fine, no eggs in the winter though. Of course, last winter was freakishly cold, and I'm glad I wasn't keeping chickens then or they would have had to come into the house! I'm bedding my current chickens in alfalfa "cow hay" and they love pecking through it. I rake it up, it makes great compost, and I'm not raking up too much dirt, and the chickens like to be able to get down to the dirt for dust baths. Of course, I'm able to move my coop when they dig big holes, so this may not be an option for you.