Much will depend on the size of your coop, the size of your windows, and whether or not you plan to let the chickens out during the day. A coop in direct sunlight can become very warm during the summer. That is much more if a health concern than the winter cold.
My present coop is small with one window in direct sunlight. It's cozy for the birds in the winter and fine in the summer if I let them out to wander. But during the hot days of July and August if I am going to be out of town and have to keep them inside, it gets much too warm even with ventilation and the window covered. I have to either leave fans running to circulate air through the coop or bring the chickens into my garage.
I put the coop where it is now because that location drains well. I didn't want to have to worry about water issues during heavy rains or spring melting, and during normal winters that location usually does not collect a lot of snow. If the coop was larger the location would be great but as things are not it has not worked out very well. So when spring comes I am going to move my coop to the north side of my house, out of direct light.
I am in North Dakota and it's been a horrible winter so far. Adult chickens can handle -30F with no trouble and can tolerate -40 for a while, so cold hasn't been a concern. But I have had seven feet of snow already and it has become a constant battle to keep the coop ventilated and accessible. I only have one vent left that I am still able to keep clear of snow and it takes about a half hour to dig down into the snow and make a space large enough to open the door to bring them food and water.