I need to show this thread to my wife. She's worried for the girls. This is our first winter with them and it's gonna be 32˚ tonight. I keep telling her that our winter isn't the issue for chickens, it's the summer that we need to be concerned about. They did fine this summer, but we did lots of extra things to keep them cool.
For tonight, I closed the windows on the coop. Thats it.
You need to ensure they've plenty of ventilation. If your window is your only source of air exchange don't close it. Moisture in coop from waste and their breathing will freeze and cause frostbite. Ventilation is to keep your coop dry and to exchange ammonia air out. Cold is not a problem but humidity and cold is.