In this area a common successful configuration for winter hive ventilation comprises three elements: 1. A reduced entrance below. 2. An auger hole at intermediate height. 3. A shavings box on top, with the top of the shavings exposed to outside air under the outer cover. The usual reason cited for this configuration is "upward ventilation", a need mentioned by Langstroth, and many since. I've noticed that very little air filters through shavings, but the shavings are damp on top, and dry below nearest the bees. Similarly, a shavings pile in our yard is always wettest just below the plastic covering on top, and wet shavings deep within the pile can be dried by opening the cover on fair days and closing it at night. Is the shaving box ventilating the hive, or is it really wicking out water, which then either evaporates or sublimes from the top of the shavings, with little actual passage of air? Water vapor is lighter than air and would collect in the top of the hive, where it might permeate the shavings. Similarly, is the CO2 produced by the bees' metabolism, being heavier than air, simply sinking and flowing out the entrance, replacement fresh air thus being drawn in through the auger hole? Bill Morong