Most nectar taken into the hive is fed to larvae; only any surplus is ‘moisture-reduced’ for honey.
It rains, we see puddles and they dry up. Perfectly natural, with little heat injected - yes, there will be a cooling of the puddle by the evaporative losses, but the puddle still dries up because the evaporated water is removed from the sytem, either by convection or by horizontal airflow.
Beehives lose heat all the time. Mostly because it is warmer inside than out. Normally bees simply change the air by fanning - cool drier air goes in and warmer, damper air comes out (larvae are wet, so continually lose water as water vapour).
That air becomes ‘damp’ because of the surface area of the frames and a normal physical quest for equilibrium between a liquid and its surroundings.
All the bees do is provide that surface area and the air flow. Occasionally thousands of bees providing a large surface area of liquid and thousands more gently providing a constant flow of air, into and out of the hive. Even so, the air leaving the hive is generally, in the UK, warmer than the air entering.
If the air entering the hive was warmer than 35 Celsius, it would simply evaporate more water and still leave the hive at the usual temperature - bees would need to work less hard at drying nectar but harder at cooling the brood nest. They only need to evaporate about a gallon of water per month (in season) in order to store sufficient honey for winter survival. Any extra either comes frm the brood, hive cooling or from an excess of honey stored at peak foraging times. For a colony in a confined space, they could not store so much extra honey - as they do for the beekeeper. They would swarm instead - removing a considerable amount of honey in the process!
The figures and rates are so variable as to not be really quantifiable from day to day - only over a long period, which is pointless in terms of hive activity, variable nectar water content, brood nest size, amount of surplus nectar converted to honey (some of which may be consumed shortly afterwards, if there is insufficient forage available), etc, etc.
Little surprise the actual latent heat energy loss, due to converting surplus nectar to honey is avoided. Mostly it is simply part of the normal hive cooling, only noticeable, by beekeepers, at peak foraging times.
However, it makes little difference to how a hive should be insulated. The first brood boxes I came across were of double wall construction. Beekeepers (always?) insulated over the crown board with newspaper or bits of carpet, sawdust (Warre), etc in the winter. Only recently, have some beekeepers forgotten, or omitted, the top insulation for some arcane reason. We now have plenty of choice for sheet insulation, so there is no excuse for omission.
Hives do lose some heat from the floor, but a lot less than above the cluster, in winter. But think about it - the air just inside a solid floored hive will be at external ambient - or thereabouts. Little different than for an OMF most of the time - unless a stupid beekeeper puts all his wintering colonies in a position of zero shelter from strong prevailing wind and providing turbulent flow beneath any OMFs. Think where the cluster will be - yep, tucked up between the frames, as far away from any draughts as they can be. Think! It is one reason why the cluster moves upwards during the winter - bees are not stupid!
Soo, to the poster who thinks they should close off the OMF, think again. The bees do not need detritus falling through the OMF to a place where it can fester and support all sorts of nasties. Yes, there is far more bottom ventilation than is required - probably by a factor of eight or ten, but does it really matter? I would suggest that, on balance, it does not.
Entrances can get blocked by snow, but OMFs will still provide plenty of air change in those conditions. Better to stop/reduce those prevailing wind type draughts than closing the OMF, IMO. That under-floor board might be better used as a wind deflector than a detritus collector.
RAB
On a passing note - does our resident ‘expert’ on the matter of hive insulation consider the difference between a live tree and a dead one, when discussing ‘tree hives’? Somehow, I doubt it... I’ve not read his paper(s) on hive insulation, as there is little, if anything, from a practical standpoint for me to gain by doing so.
I have both poly and timber hives. All are well insulated above, most timber are insulated at the ends, all are 12’’ deep, so the cluster can be well away from the OMF. There has been no top gaping holes since my first couple of seasons. Winter losses are far less than national averages and spring build-up is more than satisfactory, and I know the bees in poly (and well insulated timber) hives use less stores during the winter than lesser insulated hives.
