Winter Hive Ventilation

mist_treeNo sun – no moon!
No morn – no noon –
No dawn – no dusk – no proper time of day.
No warmth, no cheerfulness, no healthful ease,
No comfortable feel in any member –
No shade, no shine, no butterflies, no bees,
No fruits, no flowers, no leaves, no birds! –

Thomas Hood

One can find on internet bee fora long and detailed discussions about hives in winter and the problem of condensation.  Such discussions invariably focus on the water vapour given off by the respiring winter colony and frequently resolve themselves into two camps, being those who propose that extra winter ventilation is helpful and those who maintain that it is not.

What seems never to be discussed is the water vapour that comes from the atmosphere.  For those who live in locations where the winter is characterised by cold, fairly dry, weather, this is not a problem.  But where I live this is not the case.  Winters can have quite mild weather for long spells, but dryness is generally not a characteristic.  This is not to say that it rains constantly, although it can, but more that the atmosphere is damp.  It can be damp for weeks on end.  Put a cardboard box in the garden shed and it rapidly becomes soft and pliable, having absorbed moisture from the air.

As the poem makes clear, November is often a month characterised by perpetual damp but, this year, November has been largely dry, with the odd day when the air has been almost crisp. Today, however, the weather returned to type.  Large swathes of southern England have been shrouded in thick mist, airports have been closed, the sun has not been seen.  On days such as this, the air entering the hives is at saturation point in terms of water vapour and, when it comes into contact with just about any surface, condensation will form. Increasing the ventilation in a hive may not help matters if it just allows more dampness in.  If, and how soon, the dampness disappears depends on the exact location of one’s hives.  Topography and aspect are important factors. We all know how mist will form at the bottom of a slope but not the top, or on a north facing slope but not a south facing one, or in a slight hollow but not on the surrounding land. Wind is also a factor; it does not take much breeze to move mist, while spots where the air does not easily move tend to dampness.  Exposure to winter sun also helps. Bear in mind the fact that deciduous trees lose their leaves in winter, thus enabling shelter from summer sun while giving exposure to winter sun.  I’m sure bees instinctively know all these things.

So getting winter ventilation right is as much about where you place your hives as it is about what gaps you have in them.  As with all things to do with bees, appropriate placement is a matter of observing and, sometimes, experimenting.  Eventually one finds a balance that works most of the time.  Compromise will be inevitable, with both bees and English weather there is never an answer that works in all places all the time.

Gareth, Cotswolds, December

Photo: Mist Tree, Rob Hockley

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6 Responses to Winter Hive Ventilation

  1. ingrid says:

    I have about 1cm gap above the base board on my HTBH and 1 1/2 champagne cork size entrances open. There is a flat pillow in the roof above the cluster. Does this sound okay? I have left a small tray of homemade sugar ‘fondant’ in the space to the side of the followers.
    I lost all my bees to starvation by September last year having not fed them soon enough. Should this come out now or can it stay there? I notice the bees are still bringing in pollen – dark yellow. Would this ivy?

  2. ingrid says:

    Missed out asking if I should remove the sugar left in the space outside the follower!

    • simplebees says:

      Hello Ingrid

      The ventilation you have in place is more than I used to use when I had hTBH’s. But mine were in a rather windy spot and wind is very good at chilling warm-blooded creatures such as the bien, so I was always keen to excluded it and kept the bottom boards closed. Maybe your hives are sheltered from the wind?

      Since changing over to Warré hives my observations suggest that the bees have an easier time keeping the hive balanced in terms of temperature due to the vertical nature of the hive (heat rises, it does not move far horizontally). That said, I am aware of several hTBH’s that seem to manage their internal conditions rather well, but they are all in sheltered spots and incorporate considerable amounts of insulation in their construction. As it happens, they also have closed bottom boards.

      On the subject of pollen, around me the ivy stopped flowing a good while ago, but there are other winter-flowering shrubs that bees will visit, such as this.

      The fondant: it is unlikely that the bees will venture round the follower board to collect the fondant unless the weather is mild, but I doubt it will do any harm if left. Keep that pillow above the bars nice and plumped up, and check it occasionally for condensation or damp. Also, don’t be surprised to see a mouse curled up on it!

  3. Robin Morris says:

    Beautifully put Gareth.
    So pleased to see your message is on location, which we dictate when placing a hive, rather than ventilation which, to me, is interference. I wonder bees survived this x million years without interfering humans opening and closing colony vents during the winter? 🙂

    • simplebees says:

      Thank you Robin, and good to see you posting.

      In natural circumstances the bees will have whatever holes their cavity came with and they will adjust these as appropriate through the use of propolis. Last summer several of my hives built curtains of propolis across their entrances. Come the autumn, the bees removed the propolis, leaving the entrances wide open. I presumed the propolis was put in place to help guard against wasps and was removed when this danger was passed. I also presume that, had the bees preferred small entrances, the propolis would have been left in place. It is easy to assume that larger entrances give more ventilation, and this may indeed be the case, but one should not automatically conclude that what seems to be so from our human viewpoint is also so from the viewpoint of the bees. The internal flow of air within the hive is likely dependent on many different factors, not just the size of the entrance which, on my Warré hives, is some way below the bottoms of the combs. The bees will have other arrangements in place inside the hive by way of comb shaping and spacing that also affect ventilation.

      If I were to now introduce additional ventilation, or restrict the ventilation in some way, I would, as you say, be interfering with what the bees have decided they prefer. It would be rather like coming home to find that a neighbour has come in and opened the windows in your house because they feel you need some air, ignorant of the fact that you have just paid a lot of money of money to install an energy-efficient heat-recovery system that has its own ventilation independent of the windows.

  4. ingrid says:

    Thanks for the reply Gareth. I think I will close the base board up now! (We do get westerly winds – the entrances face SSE)

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