Yes - bees will certainly propolise upper vents....LJ
LJ, indeed they will.
UNLESS, you implement a couple of things:
- do use a burlap (or other compatible material) over the frames - then they will propolise the burlap layer and more likely to leave those vents alone since the vents will be considered as-if the "outside" and will be left alone (the burlap will be the nest demarcation surface then and IT will be propolised to control the microclimate); the planks are still fine for micro-climate improvement and handy to have for bee control - but not required;
- place the vents at the very ends of the hive, NOT just above the nest - the farther from the proper nest the vents are, the less incentive to propolize them; especially if the follower boards are used - the vents best are placed beyond those boards.
Not a guaranty (the usual clause), but the issue minimization.
In general I observe that in Eastern Euro, the beeks are drifting away from the inner covers implemented as the boards (with or without the vents).
The favor now days is for all sorts of soft inner covers - burlap, plastics, see-through carbon materials (including hard carbon tiles), silicon, etc, etc - the choices are many (unlike the old times when the planks were just about only an option and the burlap was more valued for other uses).
Blindly copying the old techology is not exactly good (be it "natural" to the extreme) - the best way is integration of the best ideas and materials available in time and space.
Reasonable evaluation is needed per the current context.
RE: the bottom ventilation - in my location I would not use screen bottoms.
the winters being unpredictable and brutal (as in 2018/2019) and in general dry season here - the bottom ventilation only becomes another energy drain that bees need to compensate and use stores and body resources;
the bees already are sticking to the upper parts of the frames/hives where it is the warmest - this is with minimally ventilated floors;
the 2-3 inch air buffer under the Layens/Ukrainian already tall frames (~400mm+) is plenty sufficient in my experience;
I am yet to observe "condensation on the floor" in any of my long hives - I don't know what people are talking about..
I did observe one case last winter in a square hive - the bees died in the end due to excessive moisture, indeed.
Even dry sugar was turned into mush when I found the dead-out - an unseen case prior to me;
The 300mmx300mm square hive design has very little spaces for any ventilation pockets - a consideration there for vertical arrangements needed.
