I ordered several Yokohamas this year to try and start a new breeding line but I'm getting nervous because I know they are not cold hard. I live in Utah in a planting zone 6a. I'm planning on getting them into an enclosed coop and an outdoor run, but how concerned do I need to be about them dying from the cold? How much heat should I plan on supplying for them in the winter months? All my other chickens are pretty heat and cold tolerant and I don't use heat in their coop because I'm paranoid about fires.