Regarding recent posts on this, I found the article in the Aug '17 ABJ pp.
887-889 very thought provoking (Honey bee engineering: top ventilation and
top entrances).  Top entrances are definitely de rigueur around here, where
our bees are confined to quarters from late Nov to early April, with
cleansing flight days usually rare and sometimes non-existent for months at
a time.  However the ABJ article has me rethinking how I configure things.
The core finding for me was that with top and bottom entrances you get a
large heat loss, which is actually intensified by adding insulation.  Yes,
you vent a load of moisture, but you are also venting all the latent heat
contained in that moisture, which the colony has to make good by consuming
stores.  You really want it to condense in the vicinity of the colony, so
that heat is conserved.  Quilt boxes or equivalent allow that to happen
while avoiding the cold overhead rain effect.

Top vents are not the only way to overwinter in cold climates. Finnish
beekeeper Juhani Lunden seals the top of his hives with a layer of plastic
directly over the top frames, adds an insulation slab over that, and has
two full-width *bottom* entrances (one front and one back).  So the key is
presumably adequate ventilation, and a top entrance is not the only way to
do it.  Sure, the top entrance system works, but quite possibly the bees
are hating it and having to work harder to keep warm.  The effect of
lowered humidity in the hive is probably not helpful for brood rearing in
late winter, either.  A natural colony in a tree usually has a mid to lower
entrance, and after some time the surfaces are propolised...and so non
water-absorbent. More like plastic?

Rob Hughes

Upper Kingsclear
NB Can

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