Check out the link below. The book has a lot of info on the Woods style open air coop. I built one myself, and it has really worked out for me. A 10X16' Woods will hold 40 birds comfortably. You could widen it out, for more if you wanted. It is a very well lit coop inside , with the upper windows.
Jack
http://archive.org/details/openairpoultryho00wood
Jack
http://archive.org/details/openairpoultryho00wood