Winterizing Hives; Why I Use Vented Supers
I’ve taken some heat about the way I winterize my honey bee hives. Specifically, there are people who can’t fathom why I’d intentionally put vents above the nest. And frankly I understand why they’d be skeptical, because on the surface it doesn’t make sense to encourage air flow in a hive you’re trying to keep warm. But it starts to make more sense when you factor in moisture. I’ve said it before and I’ll say it again: a colony is pretty adept at surviving the cold, but horrible at surviving the cold when wet. If you’ve ever been camping in the fall and woken up early in the morning with condensation inside your tent and sleeping bag, you can relate.
The picture above shows the inside of an inner cover absolutely saturated with water. I found this—and several others—inside hives I’ve been winterizing over the last week. What causes this water build-up? First, the bees eat honey for the energy they need to generate heat. Some of the water in the honey gets breathed back into the surrounding air. Then the relatively warm air around the bees carries the water vapor up to the top of the hive. The humid warm air hits the top of the hive, which is cold from the outside air. This is a recipe for condensation…warm moist air contacting a cold surface. The danger of this condensation is that—like the ceiling of a tent—it’ll start dripping down on the winter cluster of bees. The bees that get hit don’t stand much chance to survive, and over time these losses could shrink the cluster to the point it can’t withstand the cold anymore.
To combat this cycle of wetness, I make a “winter sandwich” on top of my hives. The picture below shows a vented super above my hive bodies. I'll plug and open the vent holes throughout the winter to try and manage the temperature and moisture inside the hives. Of the eight vents, I almost always keep seven of them plugged with rubber stoppers. The eighth vent I leave open on front of the hive—this is to discourage any air flow from crossing over the cluster while still venting moist air before it can condense. The vented super also gives me space to put fondant for winter feeding.
Above the vented super is the inner cover, which provides a top entrance in case the bottom entrance gets obstructed. Then comes a moisture board and a piece of foam insulation. The insulation is meant to keep the inner cover warmer than the outer walls of the hive, thereby directing any condensation to the walls where the bees can use it for water without it posing a significant threat to the cluster.
The Proof is in the Pudding
The most recent figures from the Bee Informed Partnership show beekeepers in my state, Missouri, suffered a winter loss of over 23% last year. Just a bit up the road in Iowa, that loss was an astonishing 54%. Meanwhile, my winter loss rate is about 5%. Honestly I don’t expect to lose hives in the winter like most beekeepers do (though it does happen every now and then). While I have little doubt that mite management plays the biggest role in winter survival, I do believe my winter hive setup—with its attention on controlling moisture—plays some role in my overwintering success. If I’m proven wrong by myself or others, rest assured I’ll change my ways, because my goal isn’t to be right about this; it’s to have each colony flying come spring.