Six to ten big birds will be happier if they are in the coop only during bad weather. Crowding is BAD!
It's easy to underestimate the need for ventilation, and more is better all year. Openings especially on the south and east sides are necessary. Having electricity out there to keep water from freezing, and if you want winter eggs, a light on a timer from 3am to 8am makes a difference.
Roofing the entire run, and having the run walls partially covered in rolled plastic, will be good for winter, and give the birds more room, and you a lot less shoveling!
Mary