A common practice has been to remove the hive cover when the bees are
packed for winter and to cover the frames with burlap or some such
porous material, the object being to allow the escape of any moisture
which may be generated within the hive during the winter. Moisture is
being generated constantly as the bees consume the honey stores, but if
the bees are adequately packed the amount of moisture will be reduced
to the minimum. The chief dancer, of course, is from moisture which
condenses, and in an adequately packed hive there is no condensation.
The temperature never goes low enough for water vapor to condense.
Therefore it is obvious that upward ventilation for the escape of
moisture is never needed in hives that are packed as they should be.
Any beekeeper who has had trouble in the past with condensed moisture
in the hives, or with wet packing over the porous tops, may be sure
that he has not provided enough packing material.
Another thing is to be considered in connection with the subject of
upward ventilation. The entrances to the hives must be greatly reduced
in order that there may not be excessive loss of heat at that point. If
upward ventilation is provided, there is opportunity for the wind to
blow through even the small entrance, through the hive and out through
the porous cover. This current of air will be slight but nevertheless
it exists, and serves as an avenue for the escape of considerable heat.
If insufficient packing is provided, upward ventilation becomes almost
necessary, unless a large entrance is left. The beekeeper must see to
it that he is providing adequate packing material before he gives up
the upward ventilation, but he should not count his bees well packed
for winter so long as he must provide for the escape of condensed
moisture.