Me back with yet another question 
We're going down to -4C tonight in the UK, our ducks like to sleep outside in their enclosure usually, when it gets below 0 like a month ago cold we put them in an inside section of our outbuilding with thick straw on the floor, some water and food, to keep them out of the worst of it at night, during the day we let them back out to the enclosure. This area has no windows for natural light though. The door has a few gaps for air.
We're planning to do the same thing to ight but we have a conundrum, we need to leave the house at 5am to get to work, normally we'll give them some fresh water and food for the day and done, I'll be back home at around 2:30pm. The coldest part of the night is at 5-7am when it's -4. By 10am it'll be -2 and back up to 0 at 12pm
My question is what to do with these two options.
1. We let them back out into the enclosure at 5, with fresh water and food but no pond. I'm worried about the water freezing between 5 and when I get home and them being stuck with no water though, and the fact they'll be outside in -4 to -2 temps.
2. We keep them in the inside section of the outbuilding and I'll let them out when I'm home at 2. We have a long lasting battery lantern that will provide them with light during the day. The water will be less likely to freeze. But I'm unsure how good the airflow is for a full night and day.
Any advice is appreciated! Thanks!

We're going down to -4C tonight in the UK, our ducks like to sleep outside in their enclosure usually, when it gets below 0 like a month ago cold we put them in an inside section of our outbuilding with thick straw on the floor, some water and food, to keep them out of the worst of it at night, during the day we let them back out to the enclosure. This area has no windows for natural light though. The door has a few gaps for air.
We're planning to do the same thing to ight but we have a conundrum, we need to leave the house at 5am to get to work, normally we'll give them some fresh water and food for the day and done, I'll be back home at around 2:30pm. The coldest part of the night is at 5-7am when it's -4. By 10am it'll be -2 and back up to 0 at 12pm
My question is what to do with these two options.
1. We let them back out into the enclosure at 5, with fresh water and food but no pond. I'm worried about the water freezing between 5 and when I get home and them being stuck with no water though, and the fact they'll be outside in -4 to -2 temps.
2. We keep them in the inside section of the outbuilding and I'll let them out when I'm home at 2. We have a long lasting battery lantern that will provide them with light during the day. The water will be less likely to freeze. But I'm unsure how good the airflow is for a full night and day.
Any advice is appreciated! Thanks!