I live in NW Montana. Chickens are out every day during the winter. It gets down to about -22 F here. I cover 3 sides of the run with clear vinyl so the birds won't have a breeze. Otherwise they hate being in the coop during the day. Food is kept in the run. Water is also kept in the run to prevent the water from raising the humidity in the coop. I have about 10 square feet of ventilation that is never closed up no matter how cold it gets. Ventilation is placed so that birds will not get a breeze on them.Yes I plan to give them the option to go out everyday year round with the exception if it’s going to be negative during the day. I’m going to have a very large covered pen for them around 10x40. I just worry about them getting frost bite in the winters overnight without insulation to hold the heat in the coop
This is the most important thing you will have to learn if you will keep chickens in the winter. A dry chicken is a warm chicken. Chickens make a lot of moisture when they breathe and poop. You need to get that moisture out of the coop. Warm moist air will make for cold frostbitten chickens. Dry air makes for comfortable chickens. A chicken can get frostbite at around freezing temperatures if the air is humid. With dry air they can be fine to well below 0. Remember that chickens wear a down coat year round. Hot days are harder on them than cold days.
That being said, choose your breeds of chickens wisely. Breeds with large combs will be more likely to get frostbite.
If you do not believe what I say, look outside at those chickadees and other small birds that spend the winters outside in your area. Do they look miserable all winter long? Their down coats also keep them warm during winter. They choose a place without drafts for sleeping at night.