My rookie mistake...not putting enough roof overhang. I had to go out and buy more materials and I am putting on a new roof this week. We are in the "deep south" so heat is more of an issue for us than cold, so we have the entire top of the coop (about a foot) of ventilation all the way around (with chicken wire over it of course). If they get too cold in the winter, we will cover some of the area (but we rarely get below the 20s).