Thanks so much for all that information! I will be out measuring my openings this week. Have not had respiratory problems yet, but only in this for four years now. Also, it will be a huge part of planning our new coop in spring!!! I sure love this site and all you chicken lovers who know so much!!!Absolutely. Chickens and other poultry are outdoor animals. They have tiny respiratory systems. They need a constant supply of fresh air.
I've been following this site a long time. There are lots of daily posts for advice about respiratory problems beginning about this time of year through January. I attribute that to people who are worried about cold and start closing up the coops.
Cold and drafts aren't the problem, stale air is.
Pathogens, ammonia, dust and fungus increase when closed up, especially if it is warmer in the coop and has higher humidity. Those things are breeding grounds for viral and bacterial infections. An enclosed coop with insufficient ventilation could have humidity as much as 30% or higher above ambient air.
Birds living in an outdoor run or in trees don't get respiratory diseases. They affect birds in tight buildings.
I have huge openings in all my buildings and take no precaution for drafts. In fact 2 buildings have those huge openings at roost height on both East and West walls. The winter winds blow right through. There is no possibility for pathogens to get a foothold.
I have never had a respiratory issue in all my years of keeping poultry.