So here is what we did for ventilation only I'm thinking now that we might need more. My husband designed it thinking the pop door would remain open all winter (we're in Alaska) but I'm not sure that they'd be warm enough.
His other thought was to install 6" dryer type vents in the gables on each side.
The coop is 6'x4' and the side vents are 6"x4'
Thoughts or ideas from more knowledgeable people than us?