I doubt that the quality of air could be a problem in outdoor wintering even without a top hole. I think the rationale for a top entrance is... 1 - to allow the moisture to evacuate the hive 2 - to allow the bees to fly on mild days when the hives are half covered with snow I would like to bring the discussion on the issue of HUMIDITY in the hive during the winter. The first question is how bad is humidity for the bees? I know it has a bad effect on the stores, combs and wooden hive parts. But how bad is the effect on the bees themselves? If we recognize that the interior of the hive should be kept dry, are there alternate ways to so other that the conventional 1 cm x 6 cm top hole. Personally I would be reluctant to eliminate it completely and lose the alternate bee entrance. Could we make this top hole smaller in order to keep more heat? Could we invent some design that would minimise the loss of heat? What is the source of this moisture? It probably origins essentially from the differential of temperature between the interior and the exterior of the hive, the walls and roof acting as condensation surfaces. On that regard, more insulation around and on top of the hive would reduce condensation. Grouping the hives would also help. The top is probably the most important surface to keep warm. Hive materials also play an important role. I am convince that styrofoam hives as our Swedish friend uses would be fantastic. I have used styrofoam mating nucs and I really enjoyed them. Styrofoam surfaces would stay much warmer than wood surfaces and not allow as much for condensation. But they are too costly for my budget and they are not available in Canada. Another old approach that could be looked at is the "moisture catcher" at the top of the hive. Wood shavings and straw have been used quite extensively in the past and have almost disappeared, probably to the benefit of newer materials easier to handle. Should we go back to using them? Would there be easier to use modern materials that would have similar absorbing properties? A hobbyist in my area found that when he wraps his hives with the top feeders still on, the interior of the hive remains dry, even in the absence of a top entrance! The condensation from the top drops in the feeder itself, not on the frames and cluster. I have noticed that the top entrance by itself does not do a perfect job as far as evacuating the moisture. (Even with 3 inches of styrofoam as top insulation.) Abundant ice on the bottom board is certainly an indicator. I have noticed the same with strong hives packed by group of 4 in the Canadian Prairies (with the same type of top insulation). Should we look for a combination of top hole and moisture absorbent? Should we reduce or redesign the top entrance? I think a scientific approach to this question would be helpful. Room for an interesting research on both the effect of moisture in the overwintering colony and ways to control it, unless somebody knows about such researches that would have been done in the past. Jean-Pierre Chapleau eleveur de reines / queen breeder vice-president du Conseil canadien du miel / Vice-president of the Canadian Honey Council 1282, rang 8, Saint-Adrien de Ham, Quebec, Canada, J0A 1C0 tel./phone (819) 828-3396; fax (819) 828-0357 [log in to unmask]