Condensation / ventilation question

I have two TBH’s. One had a large colony at the end of last year, one a small one. I just opened the small one to feed it (probably a meddling mistake but I was very alarmed how light it was). I observed that despite its excellent sealing there was no mould or condensation inside. I didn’t need to feed the other TBH, which is almost too heavy to lift, but I opened its mesh floor for ventilation. I noticed, as I have before, that a sticky liquid was on the board which had been pressed up against its mesh floor.

The question is, why should one colony have (condensation?) and the other not? And should I ventilate it more? The TBH’s both have more than one inch thick wooden walls and plenty of insulation in the roof – they are better insulated than most conventional hives. The sealing on the large colony, which had this liquid, is not perfect, it has minor leaks at the base of the hive (around the mesh).

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6 Responses to Condensation / ventilation question

  1. simplebees says:

    Could the sticky liquid be exudate (‘sweating’) from honey combs, or water that has been driven into the hive and run down to the floor?

    Gareth, Cotswolds

  2. Paul says:

    I don’t think it’s water that’s been driven into the hive – the entrance is reduced to 8mm holes and the roof is OK; and the puddles weren’t in one place, but several spots below the brood area.

    I didn’t know honey combs could sweat. If I see it again I’ll taste it. It was sticky on my fingers.

  3. johnmkubwa says:

    Paul, When an organism converts sugar to energy it releases carbon dioxide and water. Simple calculations indicate that 12kg of honey will produce 9kg of water – 9 litres of water. In my Warrés (south UK) that 12kg of honey will last 3 or 4 months over winter. Warm air holds water in vapour form; as the air is cooled the water condenses. In a hive the centre of the winter cluster is warm say 22-25 deC, or higher if brood is present. The hot moist air rises to the ceiling which if well insulated should stay warmer than the hive walls and floor. The moist air will cool on contact with cooler surfaces and run down walls and wet the floor. This water will slowly be absorbed and diffuse through the hive walls. Importantly the thick topbars of the HTBH and the Warré quilt will keep the ceiling relatively warm so the condensate does not form above the cluster and drip onto the bees and chill the cluster.. Allowing the water vapour to condense in the hive keeps the heat in the hive (This latent heat of vapourisation is the same energy released when steam from a boiling kettle is directed onto a cold metal pan- the pan gets warmer)

    Some hive systems work by having a hole in a crown board and allowing the moist warm air to flow out of the hive. The hive stays dry but the Bee consumes more energy keeping warm.
    Some Warré beeks drill a smaller hole high in the hive wall to assist ventilation and provide an emergency exit; I have found that bees will adjust the size of a 10mm hole to suit their needs (but I drill it before winter).

    Colonies do differ; strong large clusters will produce more water vapour than smaller colonies.
    I hope this simplified explanation help to understand the issue of condensation .
    John ,Over Wallop Hants

  4. Paul says:

    Thank you John,

    number of interesting points there. I’ve just read “The Practical Beekeeper – Beekeeping Naturally” by Michael Bush, who runs mainly Langstroths in Nebraska. He seems to reckon on almost 50kg of honey being necessary to survive winter (more for Italians). Nebraska is cold, but I think most of that dramatic differential shows the superior thermal charateristics of the Warre.

    The point about the heat of condensation is interesting and I’m glad I have begun making my top bars thicker for insulation. I’ll prioritise swapping out the old thin ones (that came with the hive I bought) next season.

    Do you paint your hives (which tends to act as a barrier to the wood breathing) or rely on using a particular wood to weatherproof them against our wet, damp, dank climate?

    • johnmkubwa says:

      I also used Langstroths for a few years and reckoned on leaving 40lbs (18) kg of stores for winter in Hampshire, England. Bees can survive in a draughty hive but I envisaged them doing much more shivering as they burn the extra energy to keep warm.

      In the past I have painted my hive boxes with a mixture made up of a pint of warm raw linseed oil into which is dissolved one ounce of beeswax . Initially this sheds water but it weathers off in a year or so and I re-appy it or just use raw (no chemical drying accelerants) linseed oil to hive sides exposed to prevaling wet west and north winds. This winter I have wrapped hives in tubes made from sheets of waterproof but breathable builders’ fabric (used to line walls or roofs, the roll cost 70GBPs for 50 metres; shared between 3 or 4 of us) The fabric keeps the hive wood dry and prevents ‘wicking’ away of heat during wet and windy conditions; rather wearing a Gortex jacket, or having bark on a tree.

      • mark says:


        Re: “This winter I have wrapped hives in tubes made from sheets of waterproof but breathable builders’ fabric (used to line walls or roofs, the roll cost 70GBPs for 50 metres;”

        How well did this work? And what was the brand and source of your breathable builders’ fabric?


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