Yeah, sure I have a picture or two somewhere. May try to post when I get time.
The basic concept was to try to trap as much of the bee’s heat as possible. There was a guy from England (Derekm) on here that argued that a “heat bubble” design is a superior way to accomplish that. A “heat bubble” design is something that traps the heat the bees generate and prevents it from escaping (as quickly). My implementation was basically a solid foam shell over each small wood (OSB) 4 frame medium nuc with only a small bottom entrance. Heat rises and the foam shell traps the heat inside; keeping the bees warmer on cold nights. Under each nuc was also foam, so the entire nuc was surrounded in a 1.5” foam shell. The foam was glued together so there was little, to no, air infiltration heat losses in the system.
That was in contrast to how most people tend to winter their bees. Most people have a top vent, or top entrance. Derekm argued that a top vent/entrance created a chimney effect and much of the bees heat (just a few watts in total) escaped and didn’t help in moderating the temps inside the hive.
My conclusion from running the heat bubble experiment on about 12 nucs last winter was that they DO trap more of the bees heat and if the bees to volume ratio is good, they are successful.
However there is a one very big downside to the heat bubble design (at least as I implemented it), it has terrible moisture/condensation problems. If the bees to volume ratio drops too much before spring (winter bees die out over time), you are liable to end up with a wet moldy mess.
I will not be using the “heat bubble” design anymore because of the condensation problems. I will be using a small top vent to expel moisture. If I end up with small nucs going into winter again, I will be using a top vent and giving them some supplemental electric heat on the really cold nights.