Hi and a warm welcome to BYC - glad to have you onboard.
The Learning Centre is a good place to start for all things chicken, but right now, the Coop section (just next to the Forum box) should give you an idea of what people have done in terms of coop design - the variety is mind boggling, but very interesting and inspiring. I live in Kenya so we don't do cold weather (thank goodness) so maybe other members will be able to advise. Again, if you look in the Learning Centre or type something like "preventing water from freezing" in the search box you should get some results that will help out. Similarly, if you join your state thread (type your state in the search box) it will put you in contact with other members local to you who will be happy to share their experience on coop design, among other things.
All the best