:mrgreen: :-Here's a way to rthink about this. Bees have a power budget to use to heat or dehumidify the hive. A top vent commits 100% to dehumidify unless you do something very sophisticated. A hole part way down commits less, but does it dehumidify effectively? Are there any alternatives to providing dehumidification with controlled heat budget. How about an insulated roof with a nail sealed into it? This creates a localized cold spot. Condensation forms in a controlled place and the heat budget can be calculated from the conductivity and diameter
too fine to be true.
In practice bees survive over winter. It is not so sophisticated thing.
With solid bottom upper entrance is very usefull to lead moist air out.
- when weather is cold enough, moisture condensates on cold cold surfaces.
- in wooden hive part of moisture goes into the wall and move out though the wood.
- in plastic hives moisture condensates on walls and drills to the bottom. That is why a plastic hive needs better insulation than walls that condensation does not happen in upper cover.
- use slanting bottom or arrange hive to slanting position that water drills out of hive.
- in frost weather water freezes on bottom and melts when temp is several degrees above freezing point. It means that under snow ice hardly melts.
- when temp is -20C, a lot of water vapour forms ice crystals like snow inside the hive. It melts and driples down when it becomes warm. Part of water goes into cells.
-when temp is -20C, ice crystalls stuck the upper entrance and condensation happens inside the hive.
BEES STAND THIS SYSTEM. No need to ventilate more. When hive is insulated, it is warmer and dew point is perhaps outside the hive.