honey bee management wintering

Bees benefit from an energy conservation professional

Late on the second evening of the recent cold snap I checked the outside temperature. It was 15° F, and I was very glad I had taken the nucs into the garden shed where it was about 44°. My husband asked me if the nucs had enough ventilation, and I said, yes, each nuc had a screened bottom.

At that point he became concerned about too much ventilation, to which I replied that all the other hives—meaning all those still out in the real cold—had screened bottoms with no Varroa drawers beneath. He went ballistic.

Now, I know I had explained all this to him before but, like most men, he doesn’t listen unless I’m talking about the next meal. So I explained it all again.

I’ve talked to many beekeepers who are taking the Varroa drawers out in order to increase wintertime ventilation. Since heat rises, it doesn’t drop out the bottom—and the real heat in a hive is in the center of the cluster. Many beekeepers believe the air temperature in the space surrounding the cluster is very close to the ambient outside temperature. In other words, the hive itself is providing very little insulation. It is, after all, just a plain wooden box.

My husband argued that this was close to true—but not entirely true. He said that the few degrees of difference would have a large impact on how hard the bees had to work to keep warm—and how much fuel they had to consume to do it. He said I should replace the drawers immediately. Grudgingly, I agreed. (Okay, he is an engineer and a specialist in energy conservation, but that didn’t make the whole thing any less irritating.)

It just so happened that this conversation was taking place at 11:30 p.m. Nevertheless, we collected flashlights, boots, coats, gloves, and a stack of Varroa drawers and went trekking up that blasted hill in the middle of the night. It was snowing, blowing, and freezing. Large branches and small trees had fallen across the path, and I was muttering about them—and about men—the entire time.

We slid the drawers in place at each hive. I noticed that the lower entrances were all covered with snow such that you couldn’t even see where they were, but I decided that I would wait and clear them in the morning. For the moment, I just wanted to be done.

Now, here’s the rub. When I climbed the hill the next morning the temperature was still in the teens and the snow was even deeper. But much to my amazement, during the night the snow had melted around each of the entrance holes. So not only had the temperature gone up inside the hives, but it had climbed above the freezing point—otherwise the snow would not have melted at the opening.

In the end, the bees benefited from this little exercise, my husband is feeling smug, and I am still annoyed. Still, though, I have a new problem to solve. Perhaps I will drill holes in the Varroa drawers so they let in some air—just not all the air. I modified my top-bar hive that way last year and it works great. I’ll let you know what I decide.



  • I live in Michigan where we have pretty cold winters too. I leave my screen bottom boards open year round and have had 90% to 100% survival rates for the past several years.

  • Jim,

    You see! I knew it! I’m sure my bees would have been fine as well. Unfortunately, I think my bees have risen to the level of pets–at least as far as my husband is concerned. If you think pampered bees are bad, you should see our cats (they have the run of the house) and our chickens (they have a retirement coop for when they stop laying eggs.)

    But I’m glad you wrote because it lends credence to my theory that lack of ventilation is way worse than a little cold. I’m about to remove the varroa drawers once again.

  • Hi Rusty,
    I’m not saying that a little more warmth is a bad thing. There are probably cases, e.g. low population, where warmer conditions are warranted. Indeed, I have several hives that were weak going into winter that I reduced to single deeps and put them over the top of a stronger hive. I am trying a new experiment this year. I have 60 hives and I use candy boards on top of them. The strong hives that I put the weak hives on top of have candy boards that I cut 1/16″ wide slots in with my table saw. The slots are cut through the board and hard candy. This will allow some warmth to pass up into the weak hive while still providing a candy board for the strong hive. I am aware of the potential for too much moisture in the weak hive. I deal with this by having a lower and upper entrance for the weak hive and, more importantly, insulation on the top of the hive. I strongly believe in the importance for insulation on the top of the hive to prevent condensation from collecting over the bees heads. Think of a cold glass of water. Condensation builds up on the outside of the glass because warm moist air will collect on a cold surface. Now think of an insulated mug. A little insulation has been created by air space. That little insulation prevents moisture from collecting on the outside of the mug. The same thing happens inside the hive. Put a little insulation on top of your hive to prevent the inside of whatever you have over their heads (a candy board in my case) from becoming cold and collecting condensation. But you probably already knew that.


  • Jim,

    Cutting slots through the candy board is an interesting idea. I do something similar when I stack hives. On top of the strong hive I put a 2-inch empty super. Inside of this super I put several candy “cakes” which are just disks of candy I poured into paper plates. These disks are small enough that air passes between them, so it is the same idea as cutting slots in the candy board. Then above the weak hive I put a Warre-style “quilt” which is just another 2-inch super with vent holes in the side and a canvas bottom that I fill with wood shavings for insulation.

    So really we are doing the same thing, just in a different way.

    I love to hear how different people solve the same problems. Thanks for writing. If you can get a picture of your slotted candy board, I’d like to see it. Cool idea.

  • The ideas of maintaining some ventilation and diligently preventing condensation are great. But I believe a 100% open bottom is very hard on honey bees in extremely cold weather. In nature, the bees surviving winter might have a hive in a hollow tree with a lot of mass surrounding them and a relatively small opening. They would have enough ventilation to maintain air temperature above the dew point. Their roof would be the tree above, with enough mass for temperature stability and no condensation.

    The analogy I used was: would you ventilate the house on a 15 degree F night by opening the windows and doors wide? It seems to be a preposterous analogy, but I think is is instructive. You would open the window a crack to remove excess moisture and add as much heat as you could.

    And yes, I work hard so that critters and we are as comfortable as possible.

    The Energy Conservationist!

  • Hi Rich,

    I know what you mean. When I first left the trays under my screened bottom boards off for the winter it was an experiment. I was concerned about the very things you pointed out. It has been, however, very successful. The question then, is why.

    First, I don’t think things are as drafty in the hive as your open doors and windows analogy. I do have wind breaks around my hives and, other than the screened bottom, the only other opening is a 3/8″ X 1 1/2″ notch on the front of the candy board which serves as an upper entrance and upper ventilation. So I think it’s more a matter of air flowing under the hive than through it. Hives that live in tree hollows don’t really have a need for ventilation to prevent condensation. That mass of tree over their heads is extremely fibrous and makes a dandy wick which sucks up all the moisture they could possibly create. To use your house analogy I think, perhaps, it would be more like opening a vent in the gable to allow for ventilation.

    I also wrap my hives with tar paper. On a sunny day, even though it could be extremely cold, that black tar paper gets hot to the touch. According to studies I have read it can make enough of a difference to allow the bees to break cluster for feeding. This year I am also experimenting with skirts around some of my hives to further block wind from blowing through the hives while leaving the bottom open to allow air to flow freely. Again, I would like to reiterate prevent blow, allow flow.

    My hives are about 16″ off the ground and set on stands in pairs about 16″ apart. My experiment has me wrapping a short piece of tar paper all the way around the bottom of the stand to further reduce wind velocity under the hives. Also, on a sunny day, I believe this will bring some serious warmth into the hive flowing up through the screened bottom board as the sun radiates on the tar paper skirt. We’ll see. It only took a couple of minutes to accomplish.

    Finally, I must say that you may be entirely right and it would behoove me to follow your example. I am always experimenting, learning, and relearning the best way to do things. One thing that I’ve learned is that just because something works well this year doesn’t mean it will the next. The wondrous thing about beekeeping to me is that it is as much, maybe more, art as science. Oh, and there are more opinions about how to keep bees than there are beekeepers. Cheers.

  • Rusty,
    My hives set downhill from the house, but well above the bottom of the valley. They face the sunrise, and have the hill at their backs to the Northwest where our worst weather comes out of.

    I planned to leave the screened bottoms open as you suggest. But I also thought of putting bales of old hay behind them for an additional windbreak. What I wondered was, should I put them right up against the back of the hive – oh, they are up off the ground on 2 courses of cinder block – or leave a space between hive and bale? Ventilation vs. warmth?
    Thanks! This will be a nervous first winter for me, but I’m kinda eager to get into it.


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