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Winter Ventilation

By Charlotte Hubbard

Like many women, I have trouble keeping warm. I also live in Michigan, where most people have trouble keeping warm at least a few months out of the year.

Unfortunately, that meant I overreacted the first year I winterized my hives. That November I’d put in solid bottom boards, wrapped each hive tightly in black roofing paper, reduced the entrance to about an inch, put hay bales around each hive, and told the ladies I looked forward to seeing them in the spring. They were probably dead before Christmas. I had a few other things on my mind and had never kept bees, and I totally missed the “need to vent part.” Ladies, so sorry.

I have successfully overwintered since then, and I think ventilation was a key missing ingredient.

Why Ventilation is Essential

The colony maintains heat by clustering, and the warm air from the cluster, like all warm air does, rises. When that air, containing moisture from the bees’ shivering, hits the top of the cold inner cover, it condenses and moisture drips down on the bees. Bees can generally survive cold; wet and cold—not so much.

How Much Ventilation?

How much ventilation does a colony need? Each year I’ve added more opportunities for air flow; each year my survival rate increases. I suspect there’s a correlation.

Let’s look at some of the venting options:

Hole drilled in the front of the upper deep. I used to drill a 3/8” hole; I now drill a half inch, and sometimes even 5/8” if I can’t find the right drill bit. Seems like a bee can get stuck in 3/8”, and that negates the ventilation purpose. Yes, I drill into the hive body when it is on the hive; they’ll clean up any wood shavings that fall in. They might also come after you, so dress appropriately.

Popsicle sticks (or comparable thin wood) glued to the four corners of the inner cover’s “down” side. Most inner covers have a flat side and a side with a lip, so whichever side you are putting down. I recommend Popsicle sticks since that means you get to eat the Popsicles first.

Screened bottom boards versus solid boards. Lots of us up here in sled dog territory use screened bottom boards; we just make sure there’s some sort of windbreak around the bottom of the hives (at least until the snow buries the bottom) so cold blasts don’t directly sweep up into the hive.

An absorption “blanket” below the inner cover. There are several options here, including:

A hive body filled with a few inches of filler—wood shavings, dry pine needles, newspaper, etc. The hive body has a screen tacked across the bottom so the filler doesn’t fall into the hive; it is placed below the inner cover. A homasote board, and the Mountain Camp Method are other options. There are lots of other venting options. Which one(s) you decide is up to you, although you may want to confer with other beekeepers in your area to see what works.

You can also use a Hot Box Winterizer to add warmth and ventilation to your hive. The Hot Box and moisture board have been designed specifically for beekeepers in northern climates, but can be used in warmer climates depending on the winter temperatures. Made from a pine medium super and has wire boundaries on the top and bottom, with insulation in the center of the box. For northern climates, I recommend adding this to your hive in mid- to late-fall when temperatures begin to dip below 50 degrees F. Should be installed directly on top of the top hive body. In southern climates, I recommend installing on the second hive body. The moisture board allows for cross-flow ventilation and helps to draw in additional moisture. Vapors in the hive will travel through the hot box to be captured within the moisture board to be evaporated away.

If you have multiple hives, you may also want to experiment and see which options work best. The bottom line? We need honey bees, and they need ventilation.