I find, especially when the weather gets extreme, the chickens simply will not go outside.. so you now have them living 24/7 only on the coop. Which means the coop should be HUGE.
Some end up making a more sheltered roosting area, that is connected or part of a much larger well ventilated coop.
If you roof and wall the run (but keep lots of ventilation), so chickens are sheltered in the run, that can help with space.
But in general, in extremely cold climates you need HUGE coops.
I try for a minimum of 9 square feet of coop per bird in winter.
Some end up making a more sheltered roosting area, that is connected or part of a much larger well ventilated coop.
If you roof and wall the run (but keep lots of ventilation), so chickens are sheltered in the run, that can help with space.
But in general, in extremely cold climates you need HUGE coops.
I try for a minimum of 9 square feet of coop per bird in winter.