How much ventilation to provide a hive of bees is another of those controversial issues that spans both winter and summer beekeeping. More often than not it seems that the “old-timers” are against adding ventilation, while the “newbees” are for adding more and more.
Whenever I try to assess a biological problem, I like to start by looking at how the situation is handled in nature. With that in mind, I started looking at the ventilation bees provide themselves in the wild and compared it to the ventilation in a hive. As it turns out, the two situations have very little in common, and so it is very difficult to translate conditions in one space to conditions in another.
Bees that live in the hollow of a tree frequently have no top ventilation. The cavity may open for some distance above the cluster, but at some point it is closed off. Based on this, many beekeepers think top ventilation is unnecessary.
But a tree is very different from a hive. For one thing a tree has more mass. More mass means there is a greater thermal buffer to fluctuations in outside air temperature. I know I’m not saying this like an engineer would, but a thing with lots of mass does not change temperature as quickly as a thing with less mass. For example, if you take a slice of bread and a hamburger patty out of the freezer and place them on the counter, the bread will thaw a lot faster because it has less mass.
The mass of the tree is a lot greater than the mass of the milled lumber that makes up the hive body, so the bees in the tree are more protected against rapid fluctuations in air temperature. This insulation means that condensation forms more slowly.
Also, the condensation that does form may be absorbed—to some extent—by the tree itself. A cavity in a tree may contain rotting wood or punky material that actually soaks up the condensation like a sponge and prevents the moisture from dripping down on the bees. Bees handle the cold quite well, but cold and wet is a deadly combination.
Another thing I’ve noticed is that the one opening the bees have in the wild is usually larger than the tiny winter openings we traditionally give our bees. Openings are often 3 or more inches across in the wild, or they may be long and narrow slits. In either case, they allow substantially more air exchange than the ½-inch by 1-inch opening we often provide.
What I conclude from these observations is that we can’t compare a hive to a tree. Instead, we have to compensate for the short-comings of our hives and make them do what a tree can do naturally.
The biggest shortcoming of a Langstroth hive is its inability to buffer the temperature changes which cause large amounts of condensation to form—condensation that has no way to get out.
As humans, we spend a lot of effort to get rid of excess moisture in our homes, our buildings, our cars, our factories—everywhere. We know that excess moisture is bad for human health, animal health, and the longevity of material goods. We know the excess moisture facilitates the growth of molds, fungus, and pathogenic organisms. Shouldn’t we apply what we know about excess moisture to our bees? Don’t we owe them that much?