Mine survived in an unheated, mostly uninsulated coop just fine this winter. I'm in Iowa and there is plenty of snow and negative temps to go around. The roosters did get a bit of frostbite on their combs though.
Speaking of experience...I can say that all three of my porcelains made it through some terrible -15 weather this winter, completely unphased. My coop was free of drafts, insulated and had two heat lamps. I can see if they were wind-blown, wet or whatever they would not fare well. It usually stayed 10 degrees warmer in the coop than outside, but I still had inside temps of 0 to 5 degrees.
I think because they were so active, that helped. I also saw them snuggling with my cochins for warm.
Along with flying high into the rafters of the coop = probably the warmest spots!
I have Millies and they done fine this winter. Seem to be pretty hardy We had really cold temps and an ice storm this winter (Kentucky) Didn't phase the little guys however I did provide straw and they were shielded from the elements Other than that I did nothing special and they are fine. No heat lamps or anything What a prize they are to own... I would recommend this breed to anyone who wants pet chickens Plus they are a real eye pleaser... Beautiful
I was worried about that MPC thing too after I got my hen and then read that. My one single Mille hen had no problems this winter though. Most of the time other chickens won't let her near them so a lot of the time she roosts alone. The only other hen that ever lets her sleep nearby is my only other Bantam hen and even then it's a tenuous relationship. It was below 0 a few times this winter and my coop has no heat sources except the chickens themselves. The coop is well sealed though with the only real ventilation being up near the ceiling. It stays OK in there, still darn cold but my chickens all had no problems.
Personally, my mille d uccles are very hardy. They survive cold winters, and love to roost in the rafters. I like them because of the colors and personalitys. I suppose MPC says that because of the roos big comb? My one roo did get just a tad of frostbite on the tips of his comb, but if you keep the coop at 30* or above they should be fine as far as the combs go. I insulated my coop because the weather here gets to -10 -15 in the winter at times.