It has been a while but when we kept game hens for eggs in "henhouse", we made so ceiling was very high as in close to 18'. This enabled air to stratify with respect to temperature. Extreme hot at top and relatively coeler on ground. As day progressed hens tended to move to bottom. We did not have fans so sunlight was used to drive air flow. A very important vent was relatively large and near ceiling. As sun heated roof and air below it the air began to want to rise and leave through upper vent. Movement of such air required replacement from below which tended to be warmer than average air. Ultimately all air replaced came from below. We cheated with passive cooling of incoming air by throwing buckets of water on ground near air intake and same area was also well shaded with trees. We also took into consideration the prevailing winds because wind could if coming from direction facing upper vent stop passive airflow mechanism.
