Rober, I'm very interested in this as i lost 2 hives this winter because clusters were to small and froze. In my mind am thinking if i would have had these style boxes i might still have bees ? (Don't know) in sept. i knew both hives were low on bee count ,still had capped brood and a few fresh eggs and seen both queen's. I was bound and determined not to use chem. treatment these were Wayne's Bee's. I was assuming they in a brood break because of varroa. Little did i know temps. were going to drop in the 20's. at night for 2 days, and that all it took. Don't know if a heat source or insulation would have worked.? But it sure has me thinking alot especially with weak hives going into winter. CBT had a speaker at there club meeting this month (wasn't able to attend) that was talking about heat blankets.