@CindyR: thanks for the great info. I like how your method is "simple and uncomplicated". How big is your coop? I'd leave my pop door open, too, and have been since I got them in May, but it's beside the roosting post and I think it might start to be a little too chilly for them there. Last night when I went up to check on them, one of the girls was sleeping in a nesting box, (farthest away from the pop door) which I'm assuming is unusual since I rarely find poop in the box. I don't want to obsess over this too much, since I never worry about my other pets the same way...I just want to make sure I don't (through ignorance or otherwise) put the chickens at a disadvantage come winter.