It’s getting cold, starting to drop below freezing at night, so it’s time to put out the waterer heaters. Each of the coops now has a metal water dispenser that sits on a heated base. The base only comes on when the temperature drops below freezing, to warm up the water a little, just enough to prevent it from freezing:
The coops themselves aren’t heated or insulated. It may seem counterintuitive, but providing heat is actually bad for the chickens — since a sudden power loss could result in them freezing to death. If they gradually get used to colder temperatures, they build up fat and fluff to keep themselves warm. They also snuggle together while roosting.
The main requirements for winter are to prevent the water from freezing (and thus preventing them from drinking it), avoiding cold drafts while ensuring ventilation, and collecting eggs more often so they don’t freeze (and crack).