No added heat, just a good draft-free coop with thick layer of bedding that has built up over the summer. If the wind is blowing from the north, in through the pop door, I close it at night, but the window on the south side is always at least cracked at the top for ventilation. I have a metal double walled waterer inside the coop on a heated base - and NOT a homemade one, fire danger is too much for me. The last one I bought lasted 9 years, and at around 45 dollars it is well worth it.
Remember if your birds get used to heat, and the power goes out, they may have trouble. Chickens have dense feathers and an internal temperature of 106 degrees, so they can keep themselves warm given good housing and proper feeding.
IF you do use a light or heat source, for increased laying or whatever, then make sure it is
1. Out of reach - that means chickens flying off the roost won't hit it
2. Secured in at least 2 ways, and not with plastic, string or other flammable/meltable material - use metal wire or chain, and attach 2 different ties to 2 different places on the lamp
I avoid large comb and wattled breeds up here. Mostly pea combs or smaller regular combs.
