After reading your opinions on TSC coops I've been looking into Woods coops. I don't quite understand the concept of open air but it sounds very healthy, sturdy, and quite critter proof. Since my husband has to build it and is new to its concept as well, I bought Woods book on Amazon. It explains everything in very understandable language. He has a sample chapter you can download for free before actually committing to buying the book. Also, there are various plans and designs where you can modify to your particular needs.
Can't wait to get started now.