I built my coop without them, originally, but added them later after I went in there on a hot summer day and saw the birds panting away in the nest boxes- the next week they had a nice sliding window complete with screen, covered with chicken wire on the outside to keep foreign critters out. No more worries about ventilation in the coop- they also have a fan in the summer... Moral of the story is- they need all the light and ventilation you can give them..HTH Janet