I would like to add some thoughts to this discussion, on how we can help hives of bees when the weather gets really hot.
I am still quite new to bee keeping, but did lots of studies when I was preparing to get my first hive. I have been amazed at the complexity of a community of bees which live in a hive, and realize that there is a lot of truth in a comment I saw on a blog somewhere which said something like, “No matter what you do, the bees will do as they please”.
There are some aspects of bee keeping though, in which we need to recognise some simple facts of science, and an understanding of the principles of physics which are involved. The subject of evaporative cooling is one such subject. I am still wanting, and trying, to understand all of the things which can be done – or perhaps which should be done – to help our bees to thrive, and not just to survive.
There are a number of factors which need to be considered, in this discussion, including subjects such as:
- and maybe more as well!
I would like to discuss some insights I have, which are based on actual scientific principles, rather than on “opinions” or “folk lore”. It is possible to find many opinions on beekeeping blogs. One significant factor which should be considered, when assessing these opinions, is: “What part of the world is that beekeeper living in?” What kind of climate do they have? Honey bees are kept in a very wide range of climates, all the way from the tropics (hot and humid), and hot dry climates (like much of Australia), through to cooler and cold climates which have snow every winter.
Ventilation, or perhaps “How Much Ventilation”, is a subject which fascinates me, because the ideal way, in my opinion, would provide a “year round” solution, for the particular location where the bees are being kept. What I find particularly interesting is the amount of ventilation which is available to colonies of feral bees. In hollow trees, bees frequently have only very tiny entrances of perhaps a few square centimetres. When bees settle inside the walls of a house, it is frequently the case that the entrance is again very small. And so I find myself thinking that very large areas such as screened bottom boards, or even entrances which are the width of a hive box, provide more ventilation than the bees seek in nature.
Insulation is perhaps the next factor which we should consider. When bees set up home in a hollow tree, they are surrounded by the (remaining) trunk of the tree, which may be quite thick. What is more, if it is a living tree, the sap which permeate the living tree will act as a moderator of the temperature, preventing great fluctuations of temperature. My understanding from this is that there are advantages in using thicker material for the construction of hive boxes, rather than thinner. Boxes made from material like styrofoam may have an advantage here, but this type material does not have high strength and can be damaged more easily then boxes. I do like the idea of insulated hive covers, and have built telescopic covers which have a layer of styrofoam (one inch, or 2.5 centimetres), but it is important to make sure that these covers have some sort of bee-proof liner, because the bees will chew the styrofoam away if they get access to it.
But it is so important to remember that insulation by itself does not provide ANY heating or cooling effect. What insulation does do is to slow down the transfer of heat into or out of the hive. It can slow down the penetration of heat into the hive on a hot summer day, and it can help retain the warmth of a cluster of bees when they are huddled up in the cold of winter.
That brings us to the subject of cooling, which the bees achieve by evaporating water which they bring back to the hive. Once they have evaporated the water, and formed water vapour, there is no more cooling effect possible that can be performed by that water vapour. The important thing is to get enough of that humid air out of the hive so that more dry air can be cooled and circulated through the hive. The bees will determine how much cooled air they need. We need to provide them with the opportunity to bring in the required amount of fresh air, and for them to get rid of the required amount of stale air. This is where the subject of ventilation comes back into the discussion. How much ventilation is REQUIRED? How much ventilation is too much? – or too little?
Lots of ventilation on a hot day may mean that it is easier for the bees to circulate the required amount of air. But lots of ventilation will also mean that hot summer winds will also easily penetrate the hive, making it extremely for the bees to regulate the hive temperature. Lots of ventilation will also provide difficult conditions for the bees in winter time, because cold drafts will cool them down too much, and they will need to consume more of their stored honey as they attempt to keep themselves warm enough. A beekeeper who has lots of hives will not want the extra workload of having to frequently adjust the configuration of his hives, and feral bees living in a hollow tree have no way of changing their living quarters other than perhaps to use propolis to seal up any holes which are larger than they want. I believe that the optimum answer is to provide minimum ventilation, which is enough for summer conditions, and not too much for winter. I have seen advice that hive-top ventilation is beneficial, and if it is just a small amount, it may provide for acceptable year-round conditions. I have used a small gap of a few millimetres between the top box and the hive cover, and the bees seem to be doing well. This ventilation is bee-proof, and is under a telescopic cover so that rain cannot enter the top of the hive.
Shading is the other issue which has been of interest, especially for beekeepers in very hot areas. Shading, by itself, can only prevent direct heating of a hive by the sunshine. But as already discussed, direct heating can be reduced by suitable insulation, particularly of the hive cover. Shading cannot provide any beneficial effect when a hot wind is blowing. As already discussed, hot winds will make life difficult for the bees if the ventilation openings are too large. It is not difficult to find lots of advice that bees thrive in sunny conditions. It is also not difficult to find information that the health of a hive can be compromised if it is placed in a location which has too much shade. So how do we determine the ideal compromise? A hobbyist beekeeper may easily be able to frequently or rapidly make adjustments by adding or removing shade, but that may not be easy (or even possible) for someone with many hives. My own observations, and opinion, are that shading may not be necessary if the other matters of ventilation and insulation are thoughtfully implemented.