To the OP question.
For anyone using OMFs, any further ventilation is unnecessary and downright stupidity.
The old problem was that of damp, found in hives in spring. The old adage that ''damp, not cold, kills bees'' was deemed appropriate and the best way to dry out the hive was to lose the moisture through the roof inthose days.
Warre recognised this problem many years ago and applied a sensible solution which had two very pertinent advantages, one of which is never really given much attention. His design was for a large box with low gas permeability, but nevertheless some air flow, which allowed the moist air to escape in a very gentle way, some getting trapped in the sawdust/straw or whatever the roof filling was made of. That was the solution for internal dampness.
The other advantage was simply that of insulation. The relatively large box (with low gas permeability) was a wonderful top insulation layer similar to the top insulation advocated by some of us on this forum. Yes, that was one reason why Warre system worked for over-wintering.
Yet here we are in the 21st century with some beeks advocating no top insulation and providing a through draught all winter! At least the matchsticks generally mean a flow around the edges of the hive and not a howling through-draught passing close to the cluster and creating survival issues for the bees. Yes, they are good at surviving, but will use far more stores (heat energy) and are likely to lose more bees, which fall from the edges of the cluster and perish.
So, with OMFs which, in all honesty, provide far more ventilation than necessary to keep the hive dry, no further ventilation is warranted. Indeed, the bottom ventilation could be greatly reduced for OMF installations.
I use ''matchsticks'' under the brood box (so bottom ventilation) if I need to over-winter a colony in a hive with solid floor. It works - I can assure you of that! No condensation with no draughts removing warmth from the upper levels in the hive.
Matchsticks providing ventilation above the cluster are not required and rarely add any useful benefit for the bees. It is generally inflicted on the colony after the point when the colony can effect their own fix - that of propolising any small gaps - before the onset of winter, to ameliorate the stupidity of their keepers.
I had a couple of winters with damp frames and/or too much top ventilation; I then changed to OMFs and no top ventilation (along with top insulation as an obvious progression). No problems whatsoever since then; I sometimes reduce the bottom ventilation and I do use the extra deep frames (which must be better than deeps).
This system works for me in our climate conditions. Clearly it would not be optimal in all cilmates, but matchsticks making air leaks above the cluster is a definite no-no for me.
Matchsticks used to be a poor fix for another problem (damp and mouldy frames in winter and spring) and, as such, has no place in modern beekeeping. Unnecessary, unproductive, against the wishes of the bees to give just three reasons, and so totally out of place in these days. But there will always be dinosaur beekeepers - and some of them will be trying to perpetuate their lousy beekeeping practices by insisting that this old, out-dated, unnecessary infliction on the bees is still the way to go, by brainwashing the new beeks in their section (and elsewhere). Go figure! These 'dinosaur' beekeepers don't actually think for themselves, just expect the next generation to blindly follow their poor practice and keep their heads firmly stuck in the sand!
RAB
