I don't heat at all. But I have standard sized, winter hardy, small-combed chickens. I had a couple of large-combed roosters last winter, and they did get frostbite from the cold, but it was also -25 for a number of days when that happened. They were fine, by the way. Just had smaller combs come spring.
See above about my frostbite issues a year ago. They may get frostbite here and there when it gets super cold like that. I used to lock my chickens in the coop with a heat lamp and no ventilation. The frostbite issues were far more common, and at warmer temperatures than I have experienced since I quit doing that.
We all have to do what we feel is best for our chickens, and for me not heating seems to be the way to go.