re: Randy's observation (Dec 27 11:15 am) questioning the necessity of upper entrances for moisture regulation.
I read Ari's description and do not come to the conclusion that the EPS
hives are ignoring moisture regulation. On the contrary, he described a
very precise moisture management regimen. All closed hives will have a
convection current that starts with a warm, moist column rising from
the cluster, hitting the top cover and then cooler, downward drafts near
the walls and corners. In a wooden closed hive, the warm air begins to
immediately condense and may even freeze as soon as it hits the top
cover, that is, while it's still above the cluster. In an EPS box, the
insulation reduces the temperature differential enough that
condensation does not begin until the air has been pushed (by more warm
air) off to the edges of the box. Condensation occurs primarily on the
walls. Instead of trying to avoid condensation (by venting it to the
outside), he is carefully controlling where and when it will occur. And
the sloped and screened bottom board ensures that the water can
eventually escape out the bottom without damaging the hive.
While it might be theoretically possible to construct a wooden hive
with the same convection and condensation pattern, it would be
extraordinarily difficult. It would also be quite hard on the wood
itself, seriously reducing the useful live of your hive body. If you
start from the premise of a wooden body (which you might do for reasons
of cost, durability, esthetics, etc), I think you almost have to get to
upper ventilation as your solution for moisture management. You can
only walk away from the upper
entrance when you go all-in for the fully insulated solution.
Tar-paper wrapping, layers of straw and all the other ad-hoc insulations
that I've read about here on BEE-L will not achieve the R-value or the
controlled convection conditions of a properly designed, fully-insulated
hive.
Qualifiers and context: I am a hobbyist with three BeeMax hives in
the snow belt near Cleveland, OH. I've lost my share of bees in the
winter but it was my fault (varroa mismanagement, etc). I have never
observed a condensation problem.
One further qualifier. I think you might be able to achieve similar condensation management an unvented wooden hive IF you leave
your hive-top feeder on all winter. I have done that several years now
and even with the styrofoam hives, I see indications that the warm air
rises through the cluster and into the hive-top feeder where it
condenses. But since the moisture drops into the feeder
and not onto the cluster, I don't care. The feeder acts as the moisture sink, removing the
moisture from circulation without necessarily needing an upper
entrance. The thermal mass of the feed
keeps the bottom of the feeder from becoming a secondary point of
condensation. (This technique has two added advantages - 1) that feed is
available if/when the bees get a few warm days and want to move upstairs
and 2) that I don't have to trudge through the snow to remove and store
the feeder. I can put it off until springtime.)
None of the above disputes your other advantages of an upper
entrance. There are days, sometimes weeks, when my bees are trapped
because the snow is higher than the bottom entrance.
Mike Rossander
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