I produced more nucs this year than I had boxes for (does that sound familiar ?), and until a couple of weeks ago 8 of them were still living in mating boxes - which I'd made from 10mm plywood and without ventilation, and so are not really suitable for overwintering.
But - earlier this year I'd started to make a Long Hive, divided into 4 x 5-frame Nucs for over-wintering, and - although I'm not entirely 'sold' on this idea - "any port in a storm". And so I decided to finish building it and, as I'd already cut wood for a second 'Quad-Nuc Long Hive', I've near enough finished building a second one so that all 8 Nucs can now have a better chance of surviving.
BTW - if anyone needs to see what a plywood nuc box looks like without any ventilation - here's an example:
Every one I've opened looks just like this: wet, damp and mouldy. Now this might well be similar to conditions within the mythical 'ideal' tree nest cavity - i.e. those conducive to the rotting of the tree's heartwood - but I noticed that upon opening these, that in each case the comb adjacent to the wettest and mouldiest wall of the box had been left unused, which suggests to me that bees don't actually like such conditions very much, and that perhaps they have survived for millenia despite living in tree nests, and not because of them.
But whatever the truth of that, I've now installed 3 small colonies into the following box, downsizing them from 6 to 5-frames in the process. Each 5-frame compartment has an OMF approximately 25% of the floor area, and there is 3"+ of polystyrene insulation on top of the crown boards (inner covers).
So at least now they have a better chance of survival. But - time will tell.
LJ