We thought it might be helpful to offer our experiences with regard to the insulating of beehives. Our interest was piqued after reading some magazine articles a few years back. (They are referenced at the end of this entry so that you can track them down and use them to form your own views).
We live in a delightful part of North Devon in the UK, where the summer temperature averages are around 22 degrees and those in the winter are around 4 degrees (Centigrade). It does get very windy at times. Climate of south-west England - Wikipedia. Do consider your own environment in your thinking.
In 2016, when we first started beekeeping, we followed what had been taught and what a lot of the standard texts advise. In the Summer we opened everything up, removing entrance blocks and leaving the feed-holes in the crown board completely unrestricted. In the winter we would reinstate the entrance block with its 100mm wide entrance, block the central feed-hole completely and close down the other feed-hole leaving about 3 sq.cm to vent. We would also use matchsticks to lift the crown board up slightly to provide more ventilation. When inspected the following spring, the bees had completely blocked the hole in the crown board and the perimeter gap. We thought they were trying to tell us something.
Having already embarked on the Rose Hive Method by then, we noticed that Tim Rowe (who's method it is) used solid crown boards, or cover boards all year round. We decided to block the feedholes and dispense with the matchsticks and have done so ever since.
After reading the articles referred to above, we cherry-picked some of the guidance and decided to insulate the roofs. We used 50mm PIR insulation boards because we had some left over from house construction and try not to waste anything. Hopefully they serve us well before becoming a nuisance to dispose of. There are much more environmentally-friendly alternatives available and had these boards not been laying around we would have selected one of them. The rationale for insulating the roofs is:-
The bees told us to do it (we think). They certainly didn't want it drafty up there.
The largest percentage of heat lost through a structure goes through the roof. In a wild colony there is a usually a lot of tree above the nest and so it was worth exploring whether insulation would go some way towards replicating this.
The idea of having winter stores up there in the warmest part of the hive may mean that the bees can access them a little easier and reduce the chances of 'isolation starvation'.
The moisture laden air is less likely to condense of the warm crown-board and drip onto the bees. The idea is that it will migrate to the colder walls, condense there, run down the walls and out through the open-mesh floor.
Having some moisture in the hive may be useful to the bees in processing honey for consumption, rather than having to leave the hive and search for it.
One of the articles also suggested that when the moist air condenses a little heat is given off - every little helps.
The insulated roofs are left in place all year round. We fretted about this initially and then realised that this specification was pretty much what we were living in ourselves. Our converted barn has a roof constructed with a plywood base layer with a layer of PIR insulation boards beneath a zinc roof covering. We find that the house is cool in the summer and we have yet to find bees 'bearding' on the outside of the hive even on the hottest of days. It would seem that they don't experience over-heating. In the winter the house stays pretty warm with its under-floor heating and it doesn't take long for a little 3Kw log burner to make the lounge (ours is on the first floor) nice and toasty. The tell-tale of thermal efficiency is the unmelted frost which can be seen on both our roof and the beehive roof.
We haven't carried out rigorous scientific tests to analyse the differences - but see the references which offer something more along these lines. All we can say is that we like the living conditions and the bees seem to be happy with theirs. We have not lost an insulated colony through 'isolation starvation' and they build up well in the spring.
Worth considering?
To help you decide, try and view:-
Hive Insulation by Tony Harris - P347-348, BBKA NEWS No 223 - October 2016
Reader's Questions Answered by Wally Shaw - P354-355, BBKA NEWS No 224 - Oct 2017
Winter Management by William Hesbach - P9-13 BEECRAFT Vol99, No12 - December 2017
Surviving Winter And Making Honey Needs 'A-Rated' Homes by Derek Mitchell - P375-377, BBKA NEWS No 225 - November 2018