I have a large coop for the number of hens i can (legally) keep. it is a converted garden/tool shed. i'd say the measurements post winterization/insulation project is 10x4.5x5 ft. about 45 sq feet/ 225 cubed feet total. i have 4 birds. = 56.25 cubed feet of space per bird. I read that rule of thumb was 1 sq. ft of ventilation per bird. could i have less than 1 sq. foot per bird because they have so much air space available to them?