Hello, I've read a lot about dealing with winter when having chickens, and I gather that most people don't heat the coop because the birds deal with cold weather pretty well. Just wondering how low the temperature would have to go in the coop before you'd start getting nervous? There are always those few days at some point during the winter when you get the lowest temps of the year -- around here that tends to be in the 0-5F range. So far the coop stays about the same temperature as the outside due to all the ventilation holes. Just wondering if I need to be prepared to offer supplementary heat for a few days should the temps plummet. Thanks!