I have never heated anyone in winter. I have a big shed where my large breeds and a few bantam roosters live. That one has a west facing door that is always open for the donkeys. I also have a bantam coop on the backside of our barn.
I see chickens looking cold sometimes, occasionally one is shivering, but in general they do fine. I also get the guilt, but I know nature has designed them to have a thick warm coat. Most will sit close when it's really cold, and hunker down.
I have kept silkies, and currently keep a few frizzle bantam cochins and they do fine. A few of my large breed large combed roosters get frostbite on combs and wattles. They recover fine.
Most fires that aren't houses around here are caused by a heat lamp. I'd rather my chickens be slightly cold on those bitter days than cooked chickens from a fire. I also don't need that constant worry about it. I haven't lost a chicken yet to cold weather. Be brave.