Do Chickens Need Heat?

Some people near me are worried that their chickens cannot handle the frigid cold we are experiencing at the moment. For starters, it only got down to 0.9F here last night and there was no wind. Chickens can handle this just fine as long as they have shelter from the wind, unfrozen water and dry bedding.
I have kept chickens since 1974 and we did not have electricity back then. The chickens insisted on sleeping on what amounted to a windowless window sill in our tiny goat barn. The only time they had issues was when it went down to minus 25 for three days. Some of them got frostbite on their combs. They healed quickly and got on with being chickens.
These days, my chickens have a fort Knox kind of coop to protect them from our marauding foxes, coons, possums, weasels and coyotes. There are three rooms. The inner roosting and laying room has windows to the south and a partial concrete floor, the adjoining wired and roofed coop has a skylight and is open on the east side and joins the horse stall on the south side. The third room is inside the horse barn and is where I raise chicks, when we have them. It is kind of dark unless the brood lamps are on and the hens don’t spend much time there.
When we got the (Polar Vortex!) wind advisory, I stapled plastic on the open east side of the chicken coop and the horse stall, which snugged things up. I have heated water buckets for the chickens and the horse, so they have water. I also scattered dry hay in the chicken pen and the horse stall. I use the deep litter method in my barn, meaning that as the manure piles up, more bedding goes on and it sits there, fairly dry and composting all winter. It is warmer than bare ground and the chickens love to scratch around in it. I turn them into the horse stall every couple of weeks to clean up and they help to break down the horse manure. The second horse stall, where I feed and keep the water, is kept as dry hard ground.
My 26 chickens and horse were all fine this morning. Animals get used to cold. Chickens have built in down jackets. Even if their combs freeze, they will be fine. Mara had ice in her whiskers, the same way I had my nose hairs freeze on the way out to the barn. We are all OK.
Maybe if we were to get an extended spell of minus zero temps, I would break down and plug in a couple of brooder lamps. I certainly would if we had young chicks, but the older hens are hardy and seem just fine without supplemental heat.

-Wendy lee