Is there a spec for something like number of inches above chickens' combs that ventilating openings such as this should be placed? Or just make sure they're above and not right at them? We're set in Oklahoma this week to experience a part of this polar vortex much of the country will be experiencing, and I'm trying to prepare quickly. And it's usually gusting-windy here.
I agree with the others, there's no magic numbers and what works for me might not work for you, vice versa, based on wind direction at the specific location, the external and internal layout of coop, etc. I would just aim for as high up as possible, partially to minimize chance of drafts and also to allow ammonia and moisture to rise up and escape.