So no one has a set of results comparing top entrance/vent with bottom only. Thats disappointment My own quantitive experiments have led me to seal the outside box and roof joints of our hives with cling film/saran wrap. I would like to see some other research on this, for or against.
If I was an enterprising applied entomologist, I'd get a grant to find a closed restaurant (lots around!), rent their walk-in freezer, buy a bunch of beehives, instrument them, and place a cluster simulation (heat and moisture source) in them. By varying the cooler settings I could simulate different regions, and experiment with various insulation strategies, producing a zone map for beehive ventilation/insulation like is done for plants. One interesting problem is that I have no idea what a *natural* beehive prefers (temps and humidity), so maybe I'd get another grant and a graduate student to find some bee trees, drill holes in the side, and insert probes that record temp/humidity over a year or two. That all doesn't even address the specific- and different- question of how to optimize honey production.
I'm not that enterprising, so last winter I went down to my basement, got a retired beer brewing bucket (hole on bottom and lid), stuck a 25W light bulb in a can with a tray of water on top, and put a temp/humidity sensor inside. I haven't looked at the results lately, but I dimly recall that even a small (1/4") hole in the lid greatly reduces humidity and condensation without affecting the temperature much. But if you really want to stop condensation on the underside of the cover, insulate the heck out of it. Which, in the end, is just common sense.
I tried something similar in a new empty beehive outside, but my methods were fairly haphazard and the variation in New England weather (zone 5, USA) made the results obscure. I started all this, by the way, as preliminary data before studying Warre quilts to see if I could rescue my sodden TBH, but never got that far. After looking at homasote behavior (little moisture removal from system compared to venting), I concluded the quilt was probably more an insulator than a moisture remover. If someone wants to give me that grant, I'll be glad to prove it.