I just talked with a plumber who had recently seen a warm roost idea. The inventor had placed Christmas lights in a PVC pipe, capped both ends so warm air doesn't escape and sanded the outside so the chickens don't slip off. The Christmas lights have a thermal safety switch that turns them off if they get too hot. This idea is on my "think about" list to see if it will work with the way my pens are arranged. please add other roost warming ideas and links to products that could be placed in PVC pipe to keep the chicken's toes from freezing.