I absolutely love your coop. It is a wonderful design. Gives me something to shoot for when I make my larger coop next spring.No, the chickens do not need any added heat. They are well adapted to handling cold weather. The front of my uninsulated coop is wide open year round. I get temps into the single digits, and the birds don't have any problems with it. Like others have posted, make sure you maintain good ventilation, and don't seal them up in the coop. Look at the pic below, if the chickens aren't outside, that's were they hang out, right up front, not huddling and hiding in the back. As far as snow goes, they (mine anyways) don't like deep snow. They'll come out if I clear an area for them.
Jack
