Very nice coop! I would agree that you need more ventilation, and it often works best to have openings on opposite sides so you can get cross ventilation. Keeps the coop cooler, and carries away odors. I have two 20x30 windows on my coop, and I leave them partially open in the winter, and fully open in the summer. They are protected by 1/2" hardware wire to keep predators out. I would add more ventilation to both the front and the back, and make it so you can open and close it to control how much air flow so you can have more in warm weather and less in the winter.
Keep the pictures coming!