I'm in the Greater Kansas City area. We use heavy-duty plastic crocks. Two sets. I water the rabbits at least twice a day. Clean crocks with fresh water in the morning and then in the evening those crocks are replaced with new ones and new water. The ones from morning are taken indoors, thawed and cleaned, and then swapped out the next morning - and the cycle continues. Sometimes they don't freeze during the day so then I only rinse the crocks out and give them fresh water.
Our rabbits are kept in an un-insulated metal barn / building. Has big doors on east and west sides, windows north and south. When temps are above 40 degrees and it's not too windy, we'll open doors or windows as needed to keep the air fresh. It's not an airtight building so there's still some ventilation via the eaves and the roof ridge.
Last winter, we didn't have it so bad. This year, however, all the weather "experts" are calling for much colder temps and much more snow. Guess Mother Nature is trying to balance things out from this summer's high temps and drought. Best of luck to all this Winter!