Insulation. What I do, is reduce the entrances, take off the supers, check mite levels with a sugar roll test. If the hive needs to be treated, treat it. If you don't, all of the insulation in the world won't help it! After that, I check for honey stores.Being from northeastern PA, so our winters are similar, so I usually look for one full brood chamber. Last year, I put plywood over the SBB, and wrapped the hives with tarpaper. It got all of them thru the winter. It got below zero here a few days too. My nucs on the other hand did not fair so well, but that is completely different.