Hi neighbor,
I'm in Nebraska and this is my 4th winter with chickens, so I've changed my winterizing to fit our Midwest weather . I use polycarbonate clear panels on the north side. On the other three sides I use heavy, clear shower curtains with the grommets. I secure them leaving 4" or so at the top for ventilation with the grommet side at the bottom. Halfway down the wall, I secure them to the coop again with plastic cap nails so the plastic curtain doesn't rip, so they don't flap and make noise as easily with the wind. The bottom with the grommets I attach "L" shapped screws every third grommet. This is what I changed from before. Because it can get so dusty in there, I lift the shower curtains off the L shaped screws and with Paracord attach them to the top of the wall of coop. When we are forecasted to get a blizzard, down they go and attach, when we get the 45 mph winds like today, down they go, but when we have nice weather I lift them and attach to the top, so my girls can get plenty of fresh air. Good luck and your coop is very pretty!