I'm out in Yuma as well, I'm building a 10x20 run and the coop is 4x8. Not planning to get more than 6 hens since, City limits only allow 6. I'm planning to leave the top 1 foot facing the run of the coop open with wire mesh. I bought a solar exhaust fan that I'll mount parallel to the opening mesh. Good luck and update us with your build!