Lot's of complex things going on there. But how does all this relate to a hive? The hive produces its own heat internally. It is not superheated, meaning a phase shift is not happening.
I'm not sure the source of heat is important - that a molecule of water vapour is generated by some means is where we could reasonably start an attempt to track what subsequently happens to that molecule.
Little John said, "This is where the classic scientific method is totally inadequate", I'm not sure I understand that.
Inadequate for two reasons - firstly, because the classic scientific method invariably relies upon the manipulation of a single variable, yet in practice with biological systems, there may be multiple variables involved - especially with 'whole organism' biological systems (and when such organisms have intelligence, and may react independently), as opposed to studies of muscle fibres and so forth, which certainly do lend themselves to traditional biological experiments.
Secondly, the classic scientific method assumes that conducting an experiment does not change the scenario under investigation.
For a more in-depth explanation of these and other limitations of scientific enquiry, suggest you Google "Peter Medawar - Is the Scientific Paper a Fraud ?" [in which he concludes that it is]
Returning to the molecule of water vapour (gas) within a beehive scenario for a moment - it may well be the case that such a molecule descends due to an increase of density cause by evaporative cooling. Now if we accept that this is so, then the opposite dynamic will also occur - namely, if such a molecule comes into contact with a warm surface (such as a wax comb) or other molecules of warmed gas, then there will be a transfer of thermal energy such that the effects of the evaporative cooling become neutralised, and even reversed - with the molecule of water vapour once again becoming lighter than air, and ascending accordingly.
So - if this is anywhere near the case - it then becomes a 'percentage game' - with some water vapour molecules ascending and some descending - depending upon their individual temperatures.
I hope we can at least agree that this is a highly complex situation, and one in which there are probably no obvious answers.
I think this might be an appropriate moment to remind ourselves that exclusive logic (true or false, existence or non-existence, etc) is a human invention, a creation of Aristotle which was revived and taught from the 11th Century European Intellectual Renaissance onwards. Because we are introduced to such an idea during our formative years, we consider it to be unchallengeable. We talk about something being 'logical', as if it were transparently obvious and not really worthy of further examination.
But here we have a wonderful example (I think) of a non-Aristotelian system.
Question: "Does moist air rise - yes or no ?"
Answer: "Well, it all depends on what happens to individual molecules ..."
Question: "Is it best to have an upper or lower entrance to ventilate a hive ?"
Answer: "Either will work. There is no 'best'."
The idea of two opposite scenarios being equally valid may offend our sense of what is reasonable, and that one MUST be better than the other. There are many such ideas based on the primal concept of 'The One' which can also be traced back to Aristotle - so I blame him for any brain damage ... or rather those 11th Century monks.
LJ