It sounds like it is your first winter with chickens. I took this photo when it was +4 Fahrenheit. It had been colder, -4 F overnight, but it had warmed up by the time I got my camera. The coldest these had been through was only -8 F a few days earlier. I open the pop door every morning regardless of weather and let them decide if they want to come out or not. If a cold wind is blowing they stay in. If the wind is not blowing they come out.
I hesitate to mention this as people probably won't believe me but growing up I saw chickens sleeping in trees when it was -10 Fahrenheit or colder. These were single combed full sized fowl, a barnyard mix with a lot of game in them. They were not on a bare branch overlooking a bluff squawking defiantly in the teeth of a blizzard. They were in a sheltered area out of the wind. Since they were in a tree they had great ventilation, can't get any better.
If your coop provides good wind protection and enough ventilation so the air is pretty dry your chickens should be OK. I don't know where you are located but people pretty far up north in the US have stopped frostbite problems by opening up their coops to increase ventilation.
I hesitate to mention this as people probably won't believe me but growing up I saw chickens sleeping in trees when it was -10 Fahrenheit or colder. These were single combed full sized fowl, a barnyard mix with a lot of game in them. They were not on a bare branch overlooking a bluff squawking defiantly in the teeth of a blizzard. They were in a sheltered area out of the wind. Since they were in a tree they had great ventilation, can't get any better.
If your coop provides good wind protection and enough ventilation so the air is pretty dry your chickens should be OK. I don't know where you are located but people pretty far up north in the US have stopped frostbite problems by opening up their coops to increase ventilation.