We’ve left two 2’ x 2’ windows open but screened off between the coop and the rest of the barn. The ceiling is beams and there are 3” x 12” spaces between each beam and the next (I have garden cloth closing them off.
Do I need spaces for air to move or forced ventilation?
Roof-level ventilation is great! I personally am a big fan of passive ventilation over forced air -- I grew up with too many power outages.
The air inside and outside is supposed to be the same temperature and humidity and you shouldn't be able to smell any ammonia.