How to make a moisture quilt for a Langstroth hive
For years I tried to reduce moisture accumulation in my wintering hives. Then, after much reading about Warré hives, I decided to modify a Warré-style moisture quilt box into something that might work on my Langstroths here in the Pacific Northwest.
I spent quite a while thinking about this and a long time building the quilts, but at this point I am ecstatic about the results. They are really working—no moisture at all is dripping down on my bees. The funny thing is this: the quilts are working in a way that is different from what I predicted—but more on that in a bit.
Here is what I did:
- I bought a bunch of two-inch supers that were designed to be used as mountain camp rims.
- Using a one-inch hole saw, I drilled four holes in each frame for ventilation.
- After I painted the frames, I stapled a piece of #10 hardware cloth over each hole to keep out critters.
- I bought canvas by the yard, cut pieces to fit the frames, and finished the edges so they wouldn’t fray.
- I stapled one piece of canvas onto each rim, stretching it as tightly as I could.
- I filled each “quilt” with wood chips leftover from brood rearing (chicken brood rearing, that is.)
- I put one quilt frame on each hive. In most cases I placed it above the top brood box and below the telescoping cover. In some of the hives it is above a mountain camp rim and below the telescoping cover.
For some reason my brain was muddled on the next point. I thought the moisture would wet the quilt from the bottom up. In other words, I thought the warm moist air would rise and condense on the canvas and wood chips nearest the brood nest. So I was surprised and confused the first time I opened the hives and discovered that just the top layer of wood chips was wet and the rest of the moisture quilt was dry.
Now that I have de-muddled, it all makes sense. The wood chips are light, fluffy, and basically the same temperature as the air above the brood nest, so the moist air does not condense on the wood chips at all. Instead, the humid air rises and goes right through the canvas and the two inches of wood chips until it hits the cold inner surface of the telescoping cover. Once it hits that cold surface, the moisture condenses (just like in a regular hive) and then rains back down. But instead of the drops falling on the brood nest, they land on the wood chips and are absorbed. It is just so cool!
I’ve opened all my hives several times since I installed the quilts and in each case the inside of the telescoping cover and the top layer of wood chips have been wet. When I stir the chips, it is easy to see that only the surface layer is wet because the wet chips are a yellowish-brown color compared to the dry ones which are almost white.
My original plan was to change the wood chips whenever the moisture quilt became saturated, but so far I haven’t had to. It seems the ventilation holes are allowing the chips to dry in spite of all the rain. The moisture hasn’t seeped down more than one-quarter inch.
While building the quilts I was worried that the 2-inch super would be too shallow, but it seems to be about right for this climate. I think that a very cold climate would warrant a thicker layer—perhaps a three-inch rim like those used for baggie feeders.
I should also mention that the four ventilation holes are providing the sole top-of-the-hive ventilation for each hive. Four holes may seem like a lot, but the canvas and the wood chips prevent a cold draft from flowing across the bees—the air movement is more diffuse because of the quilt. I keep a very small entrance in winter, but I have the Varroa drawers removed so air flows in through the bottom of the hive and out through the ventilation holes.