Heated waterer, wrap 3 sides and top of run and give them a handful or two of sunflower seed on the cold days (near 30% fat). That's it, we get many day below 0 F and will hit a few mornings -20 to -30 F. No heat, no problem. The key is they have plenty of coop ventilation to keep the coop dry and shelter from wind in run. A chickens comb will freeze at 32 F if the coop is without ventilation (moisture from waste and breathing).
This was after a small storm so the girls were awaiting me to finish shoveling the paths. A favorite spot they hang in winter on cloudy days is under the deck which will be surrounded by snow. I shovel an opening side of stairs for them. On sunny days they roam the paths scratching up old sunflower seed.

This was after a small storm so the girls were awaiting me to finish shoveling the paths. A favorite spot they hang in winter on cloudy days is under the deck which will be surrounded by snow. I shovel an opening side of stairs for them. On sunny days they roam the paths scratching up old sunflower seed.