I put a foam sleeve over my colonies in the winter. I can slide it on and off so I can check my colonies for food. 2 inches of foam on the top, 1 inch on the sides, taped together with tuck tape. Its not so air tight that some moisture can work its way out between the foam and the wood. The goal is to create a dome of warmth and protection and moderating humidity. On my last go round I notices a bit of moisture on top of the inner cover under the foam. But no condensation inside.