Well, it's spring and here's my report on overwintering my three box long medium frame hive.
This hive is three boxes long (48 3/4") with 33 medium depth frames in it. It has a Screened Bottom Board running the length of the hive. I put a piece of cardboard in under the SBB but it sagged a lot in the middle leaving a gap about 4" high by about 8" long most of the winter. I had three migratory covers side by side for a lid.
It came through the winter better than any of the rest of my hives. The cluster stayed in the front (near the entrance which is where the brood nest was) all winter, but seemed to move stores into that area when the weather was nice. All my hives the bees seemed to stay at the top of the hive by the cover. I wonder if it's just for the low overhead so the cover reflects more heat back? I wonder if a layer of aluminum foil glued onto the cover would help them keep warm by refelecting all that radiant heat?
Seems like the hives with more ventilation did better than ones with less. This one had that gap in the cardboard leaving a lot of air coming in the bottom. Some of the nucs had solid migratory tops and those didn't do as well as the ones with DE ventilation units on them.
The bees in the horizontal hive didn't move around that much, as I had expected, but they kept that area full of stores and the cluster came through as strong or stronger than the vertical hives.
I don't know how this will work with a top bar hive. In the long medium hive there is still that beespace at the top to communicate where a top bar hive is solid at the top. If the bees move to the top like they did in most of my hives then how will they communicate in a top bar hive? I don't know the answer to how that will work.
Most of my hives, it seems that the bees moved quickly to the top, not eating the stores along the way, but then spent most of the winter at the top of the hive by the inner cover.
Thanks for the report. I will be building a long hive this week and have wondered about the overwintering. These same concerns have prompted me to keep my top bar hives deeper than most.
I have found that a healthy vertical hive will overwinter in the same location. It doesn't move upward but will move food down into the brood rearing area. My hives reared brood on the same frames in September, January and March. The cluster stayed centered on these frames.
Sometime in March the bees begin to expand the broodnest by consuming and moving stores above the core broodnest area.