I know this is an old thread, but I'm working on the same thing here in Wisconsin. I bought some of the thick shelf liner, just not sure how wide to cut it and how far to overlap the pieces. They just have strips of fabric now - blowing in the wind. This is my first winter with my adopted flock, and the coop is in a much windier place than it was before. At least with a whole roll of shelf liner, I can afford to screw up a few times 
