We currently have six chickens, but will eventually have up to 12. Where I live (Utah), we get pretty severe winter winds and temps drop down to below zero occasionally. We are planning on building a coop that is 6 x 12. Is that too large for 12 birds? I'm concerned about building it too large - will that be too big for them to be comfortable in during the colder months? Also, how tall should the coop be? We were planning on building it about 5 feet tall inside.