Don't know where you are, but in the summer that pipe will be very nice for your birds! You might want to restrict that flow if you have cooler winters where you live. I have been thinking about the passive air condition you have in place and am quite envious of your setup. Looks like a nice home for you and your chickens.
I am sure you know but drafts should be kept to a minimum if you can, just a thought in as I don't know how much air flow or the size of the pipe you are using.
Looks like fun for sure.
RJ