They lack feather barbicels. Other chickens have those that allow their feathers to lock and keep them warm so they can be affected by cold and wet more so than chickens who have those. We do heat our coop to 40F but the adults are outside in the winter most of the time on paths we shovel for them. I just don't let them out when it's windy or below 20F.Pretty! I've never owned silkies before, but it would seem like maybe they wouldn't do as good as other breeds in the cold cause of how their feathers are?