Once it gets into low 30's mine have to make do with a cement mixing tub. And that is only a couple times a week. I use heated buckets for their water so I don't have to go out and break ice. No food and water inside.
Mine can choose to stay outside or go inside on days when it is very frigid and windy. Most hunker down behind places here or hang out in the wood shed. to get out of the wind. When it's extremely cold they all go inside early like 3:30-4pm. Ducks are very hardy and can withstand the cold but they really need shelter from the extremes. I'd never leave mine out in an ice storm or snow storm They could probably stand it okay but I feel better knowing they are all snuggled in their shaving inside their houses. I don't use heat.
But if your planning on building your ducks their own coop then be sure to add plenty of ventilation even in winter they need it to let out the moisture they create. They can get frostbite on their faces.
