it reduces heat loss and removes a feature not found in tree nests
I understand that .. but, in my experience, if bees really don't like something they tend to remodel it with wax and propolis .. if they were desperately concerned about the gap between the top of the frames and the underside of the crownboard would they not fill this space in themselves ?
I'm a very light touch beekeeper - I leave them be from September onwards and surely, if this was something that they considered productive use of their energy they would be filling the gap above the frames. I've followed you for more than 10 years now, right back to the early days when you were looking at PIR as a cheap but highly effective material to build hives from and comparing heat and humidity inside the hives, you have always made sense talking about insulation and well insulated hives...
Long before you, in1972, Bill Bielby said 'You can never have too much insulation' and 'the most effective way to overwinter bees is to ensure that the hive is well insulated and as draught free as possible' - he was a beekeeper and found this by practical beekeeping - you have done a great deal to prove it scientifically and you are probably rght that the bees WOULD prefer a no bee space crownboard at the top of their home.
But ... from a practical beekeeping point of view there seems little evidence, to me, that a sheet of polythene on the top bars with a flush crownboard on top is going to be something the bees actually NEED or at least view as essential - if they did our top bee space hives would have comb and propolis filling the gap, but it does not happen.
From the average beekeeper's point of view it would make life more difficult - disturbing the top seal perhaps in early spring to feed fondant, varroa treatment from the top down in winter by sublimation - both require disturbance at the top of the hive which I think may be less desirable from the bees point of view.
I keep insulation on my hives all the year round, I run polystyrene hives ... I see massive benefits to the bees from them being able to control the temperature and humidity and I came to this conclusion with my super insulated Long Deep Hive and rudimentary temp and humidity recording before I heard you speak at our association around 2013/2014 and what you said then was a real light bulb moment for me.
But, beekeeping is often about compromises and not ideals... I could easily turn my polycarbonate crownboards over, put some polythene sheeting on the top bars and meet exactly what you are proposing .. but, from a practical beekeeping viewpoint - not sure the benefits outweigh the disadvantages. Although, I do accept that what you are saying makes good sense from a scientific viewpoint.
