We recently winterized our chicken coop and the small run that we had built prior to giving them more room. Decided we would add a roof on the run portion and wrapped construction plastic 6 mil around the walls. We left a four inch opening on the back of the run for ventilation. The chickens seem to appreciate it as it's been somewhat windy since we did that and now today is going to be the coldest it's been so far this season. I'll add a before and after picture to this.