I have a (more or less) open coop with an attached run and a series of additional outdoor paddocks my chickens range in during the day. The coop has a living roof (insulates in summer and winter) and the run has a clear plastic roof that functions like a green house. I use the deep litter method This is my first year having chickens and this is what I've done (or will be doing) to winterize my set up:
- add a layer of mulch on the living roof, increasing the insulation
- add sun panels over some of the hardware cloth sides of the run, increasing the greenhouse effect and blocking wind
- add wood chips to the floor of the run
- add extra litter to the coop floor - adding in straw, wood shavings, and leaves instead of just the dried grass clippings I usually use
- insulate the hose that connects to my automatic waterer using foam meant for water pipes. Then I buried this just below the lawn surface in a trench lined and topped with straw. I'll be wrapping the waterer itself in several layers of bubble wrap as well. If we ever get freezing weather (uncommon in Seattle), I'll disconnect the hose from spigot and place a disposable 10+ hour handwarmer under a smaller, portable waterer. I have several portable waterers which I can swap out if they freeze completely.
- keep a good layer of leaves in the paddock, providing a warm mulch layer for insects to live under; and hours of foraging activity for the chickens
- get a few bales of hay from grocery stores after they take down their Halloween displays and stack them up on the outside of the coop for extra insulation - just in case

- throw some BOSS in at dusk (my girls are corn-free for allergy reasons) to generate extra heat, keep their crops full
- I've also been harvesting comfrey all summer long and dehydrating it, so I have an extra source of greens to feed