Every winter we struggle with moisture in our hives. This year we are using a new method and it seems to be working quite well.
We have empty boxes on the top of each hive. We drilled 3″ holes in the top board of each hive to allow moisture to escape. We put mesh over each hole so that the bees couldn’t enter the empty top box.
Using jute, we sewed together bags that were approximately the size of the box. We filled the bags with coarse wood chips. We purchase ours in large bags from http://mvep.ca/ They are spruce/pine chips.
You can buy them from feed stores or pet stores in the city.