@jsmith, my coop is 10x12. 8 foot high ceilings. My chickens do not like a stiff cold winter wind but there is a big difference between a nice cool breeze and the wind at -30 or-40. In the summer they roost right beside the open window which is above the pop door but in winter they move to the west window that I close then, it's also away from the pop door. The roosts are high enough that winter drafts from the pop door don't seem to reach them. All winter they are in and out of the coop, on really windy winter days they stay inside and I'm sure some cold breezes get in through the pop door but it doesn't seem to bother them at all.
It's probably not wise to raise delicate chickens without heat, Seramas come to mind but my chickens are a mix of bantams and large breeds (Barred Rock and Welsummer) and are very hardy. The bantams are mixed breeds and may come from some fancy little bantams that my sister raised but they appear very hardy as well. Perhaps because they have been raised without heat and adjusted.
Sometimes we over-coddle to the detriment of kids and critters. Keep it simple. That said I would be wary of raising the delicate breeds without any winter heat. Of course my winter is very different from a Texas winter where I would probably not give any kind of chicken heat in the winter.
It's hard to say why your hen would sleep in a nest, is she going broody?
Look up breeds online to find out which ones do well in cold climates. You might want to hunt up an article on ventilation by a lady who raises chickens in eastern Canada. Very informative. Big difference between direct drafts and ventilation.
Hi CindyR... Any chance you know the ladies handle here on BYC or what the name of the thread is ?