My birds live in a three-sided coop, year round (new coop with a "real" house almost ready!!!). The house faces south with the run extending to the south so the prevailing winds are blocked. The house is insulated. The roost is a 2x4 laid flat so they roost on the wide side. It's about 4 feet off the ground so it's sort of up under the roof. On cold/windy nights I keep tarps up around the run (which is also roofed). Most drafts are blocked, but there is certainly plenty of fresh air!! We always have a couple of weeks in the low twenties/teens/single digits, most of the winter in the low/mid twenties. When I go in there early in the mornings, it's very much warmer in the coop than outside, even with just tarps around the open sides. My birds do fine. Their first winter, several of my hens didn't grow back the feathers broken off by the roos, and went through the entire winter with bare backs. During the really cold days, I did put a heat lamp on one corner of the run so they could warm up but they didn't really seem to use it. A little bit first thing in the morning when it was so cold my nose hairs froze, but I ended up taking it down after just a couple of days. As long as they have a sheltered spot to get out of the wind, they should be ok. I did keep lots of litter in the house portion of my coop and had to put out new water two or three times a day so it didn't freeze.