I am thinking of just insulating my coop's ceiling also, but I have went through 2 winters with my flock in an uninsulated coop with only a 75W and 50W red light bulb and water heater for heat, and have had no losses due to cold. The rooster's comb and a couple of the hens got nipped a little bit, but the hens did not stop laying. I have a temperature sensor in the coop and I think the coldest it ever got in there was -22 F., for a short period. The chicken's body heat keeps the temp in there about 10 degrees above ambient, even with good ventilation and no insulation. I do reduce ventillation in the winter, but not to the point where I get condensation. Snow on the roof of your coop will actually act like insulation. I never get any snow on my coop's roof because it is under my deck. I think you will be fine without insulation. The hardest thing for me about winter is keeping the water from freezing, but my waterer base heater does a good job of keeping my 5 gallon galvanized steel waterer from freezing up, even if it gets to 30 below or colder. It also adds a little heat to the coop. I have a long extension cord run out there but maybe someday I will run conduit and wire. The water heater only comes on when it gets below 40, and I have my red bulbs on timers so they only come on in the early morning hours. It seems this setup raises my electric bill about $10 per month in the winter. Hope this helps!
