Hello all, after several years of reading I have signed up to post. I am a hobbyst (8 wintered hives, doubles, wrapped and top vented) located in Ottawa Ontario. I have followed with interest many topics related to northern beekeeping.

Michael's description of a well prepared hive is bang on for my area but I have some questions about the need for a fully open bottom entrance vs a reduced bottom entrance.

" A wide open bottom entrance, protected against mice, insures adequate ventilation. Reduced 
bottom entrance increases in hive moisture...if you want vapor to escape 
the top of the hive, it must be replaces with air from somewhere else."

My thoughts are that a bottom entrance as big as the top entrance should be ok for exchange of air. The incoming air will be colder, dryer, and condensed. The exhausting air, will have a higher RH, be warmer, and less condensed. Because of the coefficient of expansion of air as it warms, a smaller volume of air will enter then that which exits. How much air that enters the hive depends on how much air exits? The air will be pulled through the hive. 

The inside of the hive does not have a uniform temperature. It will be almost as cold as the outside temperatures at the hive walls and where the air is not in contact with the cluster. The convection currents inside the hive will likley change as the cluster expands or contracts. Some of my hives have a special winter inside lid that has a "tunnel" like exit that extends 1/3 of teh way to the center. This top exit is closer to the center of the cluster and should catch the warmer air rising off the cluster. 

Thoughts?  

Peter

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