Hi Elle:
I'd recommend against putting them in a building. Instead I would try using a 'quilt-box' on top of the hive (langstroth) to protect them from the snow.
Here's a cut & paste of my post from a similiar
thread:
https://permies.com/t/135246/Bees-Winter-Cold
It can be done, but shouldn't be necessary if you have a healthy colony.
It may even be detrimental to keep them in a building. If it warms up too much inside the building when it's still cold outside, the bees will leave the hive thinking it's a nice day for a flight.
They go outside, get chilled and won't be able to make it back to the safety of the hive & die. Fewer returning bees result in a weaker hive. A weak hive is more likely to freeze to death.
Best to keep the hive healthy (inspect for diseases), well-fed, sheltered from the wind and be sure to keep them dry (ventilate the hive).
Most of the colonies I lost were due to condensation build-up in the hive. Cold, wet bees =
dead bees.
Using screened bottom boards or quilt boxes will help prevent suffocation from snow build-up. They also do wonders to keep the hive dry.
I'm using a screened bottom board on one hive and a quilt box on the other, both are nice and dry.
They are easy to build, here's a few links:
https://www.honeybeesuite.com/how-to-make-a-moisture-quilt-for-a-langstroth-hive/
https://www.tillysnest.com/2014/11/diy-winter-beehive-quilting-box-html/
https://cityboyhens.com/2015/03/06/how-to-make-a-screened-bottom-board-for-your-beehive/