When I first built my coop one side was going to be for chickens the other for storage so I insulated the chicken side (walls and ceiling). Chicken math being what it is the last 10 winters I have had to have more room so I removed the door between the two rooms and the chickens are now occupying both sides. The noninsulated side, which is the northern side of the building, has just cardboard stapled to the rafters to keep the birds from getting above the ceiling on the other side, a single window and the entry door. I haven't noticed a bit of difference in where the birds hang out--both sides have nests, a roost, feeder and waterer--nor have I had any problems with the birds. I have noticed that the waterer on the north side will freeze when it gets down to 20 below even though it, like the south side one, has a galvanized heater under it. The coop is well ventilate by lowering the upper windows to about 3 inches on all four sides. So I guess it really doesn't make any difference.