It's my first winter with chickens, too. I have an open air coop with a big hatch on the back wall above the roost bars I leave open, and even with temperatures plummeting down to single digits and with icy rain, they've been fine. They're out foraging in the snow right now. The only weather-proofing I did was put an immersible heater in their waterer and put some fresh leaves on the snow that got into the coop. I have upped their wet mash amount in the mornings. I haven't seen any signs of distress and no frost bite on any combs or wattles, not even the rooster's. I do notice that the 12 of them pack in pretty closely at night.