Right now my chickens have 2 outdoor coops, surrounded by a large fenced in pen which we are slowly adding a top to. The chicken pen butts up against the side of the barn. Today, we decided that once we get it all done, we are going to build another coop INSIDE the barn. It won't be as large, and I think we can install a small door, similar to a dog door that will go through the side of the barn into the pen.
That will allow my girls to have a warmer winter home (and save on electricity for heat lamps, since the barn is warmer during the winter) and also give me an easier way to separate out the older hens from new chicks.
If we design it right, it could also double as an area where we could keep a bobby calf if need be.