![]() However, gases are able to move through cork by diffusion, so it can reasonably be described as ‘breathable’. Cork is made up of air-filled closed cells, so there is not an obvious route for air to flow through and it is frequently described as ‘impermeable’ to gas. ![]() The literature is not consistent in its description of the permeability of cork to gases such as air. ![]() Cork also has the advantage of being light, so that the insulation can be improved without a huge increase in weight. The thermal conductivity of cork is in the range 0.037 to 0.04 W/(mK) – ie this lower value demonstrates that a given thickness of cork insulates as well as almost three times the thickness of western red cedar and more than four times the thickness of many other woods. Other woods typically have values in the range 0.14 – 0.3 W/(mK). The thermal conductivity of western red cedar, generally recognised as the best material for hive construction, is 0.11W/(mK). My initial thoughts were to use extruded polystyrene, but when Gareth said that he’d bought cork boards from this convenient supplier, this struck me as a much more attractive material. I therefore decided that I should insulate the hive properly for the coming winter – with the expectation that the hive would also benefit from insulation should next summer be as hot as this one has been. When this hive was the first OxNatBees colony to swarm this year, I attributed the health and strength of the colony at least in part to the added insulation. Looking for a use for the cardboard, I packed it in large polythene bags which I fastened around my occupied hive, underneath, on top and on all four sides. When it arrived at the end of January, it was packed in a large cardboard box, and surrounded by masses of shredded cardboard to protect it in transit. ![]() Last year, I was given a colony of bees in a top bar hive and I decided over the winter to buy a second hive. Reported benefits include reduced expenditure of energy by bees in cold weather and fewer condensation problems, leading to lower colony losses over the winter in insulated hives. There has been considerable interest over the years in the use of hive insulation to provide an environment for the bees that is closer to their natural habitat of the interior of a hollow tree trunk. ![]()
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