On Dec 18th Derek and Elaine Mitchell gave DWBKA an excellent talk on the benefits of insulating our hives. They argued that we have been doing it all wrong since the National was first introduced in the 1930’s when a light and easily portable hive was sought. Their hypothesis is that given a choice in the wild, a colony of bees will take up home in the middle of a large tree trunk and thus have a tall thin space with thick walls. Their entrance would be at the bottom. The thick tree walls insulate the bees in winter and summer and thus the nest stays warm enough to avoid clustering and the need for large amounts of stored food to be converted to heat. This is in stark contrast to the National Hive.
Of course, if they do not need to convert all that food into heat, they will produce far less water vapour. With less water vapour around and a warm ceiling there will be much less condensation and, as we know, condensation is not good for bees.
They go on to argue that because there is less condensation there is less need for ventilation. We currently ventilate because there is high humidity and a cold ceiling which together produces condensation. In doing so we further chill the colony.
So, the Mitchells are arguing that we should insulate our hives, especially the roofs, and reduce the unnecessary ventilation.
Derek Mitchell has written various papers on this subject. One can be found here.
There is also an excellent article by William Hesbach in Bee Culture ~ the Magazine of American Beekeeping, October 21, 2016 The article is based around Mitchell’s work but is written in easier layman’s terms. I recommend it as an interesting and readable read.
So, following the talk I set out to build three insulating jackets, or Bee Cosies as we call them, using roofing insulation materials which are relatively cheap, structurally sound enough and not bothered by rain.
Materials – all found at Jewsons but I am sure other stores are available
Recticel 50mm Eurothane Eurowall cavity board 1200x 450, ie, a size I could put in the car at about £7.00 per sheet. The cavity board comes in other thicknesses but 50mm seems good.
Evo-Stik “Gripfill Xtra” glue at about £4 per tube.
Gripfill is excellent. It comes in a large tube like a silicon filler and can be used in the same way to fill any gaps and also to glue the bits together.
Pakex insulation foil tape 100mm wide and 45 long at about £11.
The aluminium tape works to seal the surfaces and hold them together and apparently the bees don’t eat their way through it. (Mitchell did suggest that bees are boring insects.)
Wooden barbeque sticks as extra scaffolding by pushing them through the joints to help hold things together while the glue set.
PVA All exposed eurothane surfaces were painted in a thin PVA mix to try to seal them before gluing.
Following Derek Mitchell’s advice, I was basically making a large box to cover all or most of the hive.
I set out to make the inside 10mm larger than the National on all sides, so inside measurements were 480 for each side and I kept the width of the board for my depth, ie 450mm.
They can be assembled in various ways. I prefer to have all the joints angled at 45° to get the maximum area for joining the sides and roof. The sides and roof were thus 480mm long on the inside and 580mm on the outside. The tops were also chamfered in this way but bottom edges were kept square. This uses more insulation and creates a good deal of waste strips, but feels sturdy. Alternatively, assemble the sides and roof at right angles ~ it seems to work well too. The penultimate bit of construction was to tape all joints and corners and exposed foam with the foil tape.
The insulation works by keeping the wooden hive dry, reducing wind and reflecting infra-red back into the hive. The better the silvering on the inside, the better will be the reflection.
Once completed, I let the boxes air for a couple of days to reduce the smell of the solvent in the glue before putting them on the hives and checking the access for the bees.
A final refinement which I have yet to implement is to put a strip of 25 x 25mm wood all around the base of the hive as a small shelf on which to rest the Bee Cosy. This will, in effect, close off the air gap around the hive and thus give a crude form of cavity wall insulation. For the Nuk I cut a 25mm round hole in the insulation directly opposite the current entrance hole.
Spare insulation wrapped in bin bags was put on the roof and the original hive roof put on top of that for added weight and weather protection. These last two steps are probably unnecessary but you have to put these bits and bobs somewhere! We also have lovely green woodpeckers around, and hence the chicken wire to keep them out.