"Cold" is a relative thing. We asked a poster once and they said 45F. But they were in Georgia or somewhere. That was "cold" to them, but would be balmy sunbathing weather in a lot of places.
There are a few key issues with the cold, which chickens can handle really well. When they get into trouble, it is due to frostbite, and that comes from an excessive amount of moisture / humidity inside the house. The solution to that is to open up the house....provide ventilation...... to let the moisture escape. That runs counter to most folks logic, so they don't do it and the birds get in trouble because of it. BTW, source of the moisture is the birds themselves. Mostly their breath but also their droppings.
So there is well ventilated, then there are drafts. Drafts appear as an excessive amount of air movement inside the coop that ruffles the feathers. So the goal is well ventilated, but free of drafts. Excessive drafts work like wind chill. We feel that too. On a cold windy day, things improve a lot if you can get out of the wind.
Lastly, once temps drop much below -10F, birds with large combs and waddles, will get into trouble due to the large exposed area. Birds like leghorns, etc. So in USDA zones 4A and colder, it may be a good idea to keep cold tolerate birds.
BO's may be that.