We have ventilation on the sides of the house where the roof sticks out, and a little crack at the top of the door, other than that that is all. We have 9 chickens in all
Might want to do some measuring/calculating and see if there's enough to close the windows at night - for your flock, 9 sq ft would be recommended minimum. I still meet ventilation recommendations with windows closed, but having them open more than doubles it, so worth it for me to have them open.