I have a question though, you mentioned that you use top entrances in winter. Wouldn't you want to do the opposite so the heat would stay in the hive?
Condensation is the main problem here in the North, not the cold. As the bees consume honey it produces warm moisture that rises to the top. Without a top entrance/vent, the moisture condenses on the underside of the cover. If you get enough of it, it will even drip. The bottom line is it will elevate the humidity level of the hive and greatly increase the chances of dysentery.
Since heat rises it would be trapped at the top. If you open the top wouldn't they have to work harder to keep the heat levels? I am not being critical, just looking for enlightenment.
Yes heat does rise, but by completely closing off the bottom of my hives, I am basically doing the same thing as you described above about not having an upper entrance, but only in reverse. So yes they do loose heat, but without any bottom ventilation, the air flow is minimized.
I am not being critical, just looking for enlightenment.
No offense taken, the open discussion is beneficial to everyone. I think you hit the nail on the head when you discussed Northern hive management methods being used in the South. The bottom line is local climates differ so within the USA that there is no right or best method that covers everyone. Everyone must keep that in mind and use the management techniques that work best for them in their location.