OK, you all can do what you like, but for me, I'll be doing the following:
1. I have five roosting rungs on my roosting ladder. I will be buying five heating pads, and duct taping them to the rungs. One for each rung. On the top rung, I will set the temp on "10" for super duper warmth! The lowest rung will be set on "1". The others will be in between temps.
2. During those cold months, I will go to the hen house at 8pm. I'll lift each hen from it's perch, weigh it with a small digital scale, and the lighter ones I'll place on the top rung, and the heavies will go respectively further down, as they'll be generating less natural body heat.
3. I will work up a mathematical algorithm, based on body mass, for giving each individual hen, a cracked corn snack while I'm out their weighing them. So...thus far, for your review, I'll go out to the hen house at 8pm, and I'll turn on their heating pads, I'll then weigh them, snack 'em and stack 'em!
4. I'm not done! Since my wife has some old pantyhose she no longer wears, I'll salvage that. Yes. I'll throw a few stitches in some of the beanies I'll be making. Let's face it, some birds have large combs that get cold. Their out their flopping all over the place loosey goosey. I figure, as long as I'm out their weighing them, snacking and stacking them, I may as well slip on a few custom-fit beanies on their head. Since these are sheer pantyhose, they'll be fit on the hens heads like little bank robber masks, yes indeed! Right over the whole head. That way, their combs won't be shamelessly dangling every which way like some floozy, just begging jack frost for a bite.
So, just for a moment, imagine in your minds eye, how comfy-cozy all my hens will now be. Since you can see through pantyhose, some hens can stay up late into the night, just looking around (and not be cold doing it)! Which leads me to, that's right, #5!
5. Finally...I have an old 13" tv set (with built-in video player) we no longer use. Hey...why not! I'm going to make a video of things like pasta being made, worms crawling through soft earth, sun drenched sand dunes , etc. I say, let those with beanies stay up late watching the Chicken Channel!
I think it speaks volumes that so many of you are such thoughtful and conscientious owners of your birds. Truly! Your worry may be warranted or unwarranted. I really can't say, and I'm sure that such variables as breed, age of the bird, current immune system status, etc, all play a role: one which we can't always measure. I suspect that most chickens that appear to have substantial coats and a healthy gleam in their eye during daytime, may be able to handle bitter cold just fine. After all, most birds come with remarkably similar coats, and it gets bitter cold over that vast majority of the planet. Only a few species migrate. However, the colder it gets, the more it will likely push that cold-survival envelope. All things have their limits. Just don't over-do it if you use heat. I may cause harm.
Brian