We have cold, hard winters here. Ducks in cold weather need
1. Shelter from wind
2. Shelter from rain and snow
3. Plenty of ventilation to prevent buildup of fumes and moisture. Moisture leads to frostbite and tissue loss.
4. Protection from predators (that become even more interested in ducks when other prey are hibernating or migrated for winter).
5. Dry, deep bedding for heat retention and insulation.
6. An unfrozen clean water source deep enough to dunk their head.
7. Nutritionally balanced food that makes up in nutrition for the loss of forage material and insects that go dormant in winter. Even free range domestic ducks need nutritious feed year-round to make sure they get everything their bodies need for health. They have been bred to be kept by humans and have different needs than wild ducks.
A duck house should be low to the ground and offer shelter from wind, rain, snow, etc., on the lower walls, while having a means of venting fumes and moisture higher up. Ducks expel a lot of moisture, both in poop and in breathing, so plenty of ventilation that is up higher, under an overhanging roof that protects from rain and snow, is good. I tarp the windward side of my duck house and run for the winter, leaving the rest of the ventilation open.
A duck house should also be predator proof, with ventilation windows covered in half-inch or finer hardware cloth to prevent predators from reaching through and grabbing and killing your ducks inside their house. Any opening larger than 3/4 inch should be covered in hardware cloth. If mice can get in, so can weasels and snakes. Once inside, any predator will probably kill or injure all of your ducks, even if they don't eat them and can't carry them away. The bottom of your duck house also needs to be protected from digging predators. If a two-year-old child can figure out how to get in, a raccoon can get in. Raccoons are deadly to ducks. I know this from personal experience.
I would encourage you to think about your situation in light of the information people have been providing and consider whether your current plan is likely to meet your ducks' needs or whether you want to make some adjustments to it. I don't know where you live or what your duck house looks like, so I can't give more specific advice.