I've got plenty of ventilation but it's still hot as an oven in the coop, so I propped open the human door as soon as we got up and it'll stay open like that until about 9 PM.
Unfortunately my coop is placed so it creates shade... which means it's taking the brunt of the sunlight, not helpful on a day like this.
Lack of natural shade is why I have a picnic fly over the coop and over the brooder.