i know this has been mentioned in the past,but can't recall the details.michael,i think you're a big fan of these?
Do you mean wraps? Do you mean insulation between the inner and outer cover?
I've actually never used either. I try to provide some ventilation and I've never wrapped. Maybe wrapping is a good idea. But my experiece is that on a warm day as it is the bees try to fly and end up on the ground from the cold. I always figured if they got warmer from a black cardbaord wrap they were even more likely to do that. Now that I have an observation hive where it's warm inside, though, I don't see any more or less of that behavoir because of the heat, so maybe it's a good idea to wrap.
Insulation is in the same category. Maybe it's a good idea, but I've never done it.
I'm a big believer in insulatio on top of the hive. We use half-inch R-board but it can be anything. It's just like your house. If the snow melts off the roof, you are losing too much heat. The bees have to consume their stores to generate that heat.
My single hive survived last winter in spite of many weeks of intense cold. I did not wrap, but I did put foam insulation on the inner cover, partly to control condensation. The hive was beside a large spruce, for wind protection from the west, and I had two deeps and one super for stores. I hope my methd works this year, too!