So you built your coop and need more ventilation and Winter Is Coming. For whatever reason there is just nowhere that you can cut a hole and cover it with hardware cloth without it blowing a draft directly on your chickens. You already know that's not good. Neither is warm moist air that is unable to escape causing condensation, causing wet hens and roosters, causing frozen feathers and combs, causing frostbite. So now what?
Don't be baffled. Build Baffles!
What in the world of coops is a baffle? It's something that blocks wind from entering a permenantly open window. Just what you need, right?
So, pick a spot along the top of the wall. Cut your window. Don't forget the hardware cloth. Now attach a board, no less than 2 inches think, along the top and both sides of the window, not along the bottom, a three sided frame if you will. The side frames should extend past the bottom edge of the window a couple of inches. Next you attach the material of your choice to fit the frame. Plywood is the obvious choice but may I suggest plexiglass? It can then double as a window. This is cut to fit the 3 sided frame with the open bottom edge extending past the bottom of the window just like the side frames.
Ta daaa! Baffle! No wind can blow in yet warm moist air can rise, escape out the window, and flow down and out the open bottom of the baffle.
I made my baffle a bit different. I had a too small coup with attached run. I covered the run with plywood in an effort to increase coop size. Closing it in meant I needed more ventilation.
The edge of the gabled roof made it easy since it stuck out a couple inches from the wall. The wall inside that gable was already covered in hardware cloth. I only needed to cover it with plexiglass.

I miscalculated and didn't make it wide enough so I filled the corners in with scraps. It has worked very well.

Are you baffled now?;)