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From:
Allen Dick <[log in to unmask]>
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Date:
Sat, 28 Feb 1998 11:41:33 -0600
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> >In my recent post I was referring only to the *supers* area in a hive and
> >have found that ventillation there does no harm in a *warm* summer, but in
> >cool summers it is a bad idea.  Who can tell what the weather will be in
> >a few days.  I can't -- in Alberta at least.  Frost in June and August is
> >not uncommon.   On cool nights and rainy or windy days I want my bees up
> >working in the supers, not hunkered down in the brood boxes
 
> I had understood that the bees *do not* heat the inside of the hive, so
> why would it matter if there is top ventilation or not?  If it's frosty
> outside, wouldn't the bees be in a cluster anyhow even without top
> ventilation?
 
Well, like most generalities, the above one about heating the cavity is
only generally and literally true. Moreover,  it is subject to wide
misunderstanding.  Just because honey bees do not actively heat the cavity
they occupy does not mean that managing temperatures in the hive by
controlling volume, insulation and openings will not result in healthier,
more prolific bees.
 
Bees naturally toggle between *passively* heating the whole space and
heating only their cluster just by virtue of interaction of the following
factors: 1.) the mass of bees and brood and their metabolic heat, and 2.)
the size, insulation and ventillation characteristics of their home.
 
Since the bees -- like all organisms --  do give off heat, and because a
given cavity will warm or cool in relation to the total heat output of the
bees in it, it follows that a smaller insulated cavity with small holes
will be at a greater interior temperature at all times than a larger, less
insulated, draughty enclosure.
 
The approx 55 degree cluster temperature of bees is the toggle.  When the
interior temperature crosses this line the bees suspend work and withdraw
to cluster for warmth or break out of cluster and resume work in
the farther reaches of the hive -- depending on whether the temperature
trend is up or down.
 
Therefore in the warmer cavity the bees will remain active and unclustered
longer as the outside temperature drops.  Active bees make more heat, and
thus the effect has a feedback component: a warmer hive results in a
warmer hive results in a warmer hive results in a warmer hive etc...
This can be a problem if there is no way to dispose of the excess heat,
and this is what many -- especially in the South where it is a real
concern -- focus on, often neglecting the problems associated with
sub-optimal heat retention that can be a problem in most other areas.
 
Obviously in hot conditions, excess heat can be a serious problem.
Interior hive temperature of about 93 degrees F is ideal. There is an
ideal humidity too. Above these limits, bees stop other work and start to
dump heat and moisture by fanning.  Below these limits, they may block the
entrance with their bodies or propolis or recede from the opening.  Our
goal is to select a hive volume and entrance size for our geographic
region that allows the bees to maintain the interior at a temperature
above clustering and below fanning temperature most of the time.  We also
must avoid -- even once -- approaching meltdown.
 
Generally, in active season, bees do best in spaces where they can control
the temperature of the whole cavity in the middle of the comfortable range
-- where they neither have to withdraw to cluster for warmth or fan for
cooling.  That's why we don't make baby nucs in standard supers or leave
extra supers on in the winter.  This is common sense and obvious too, when
you think about it.  Therefore, in summer, if the volume and ventillation
are right, the bees will be able to remain unclustered most of the time.
This means more work is accomplished, more foundation drawn, more honey
ripened, more cells cleaned, more burr comb built, etc...
 
Nonetheless, the necessary volume and entrance size of a hive is
determined by more factors than just the above: we have to allow for
expansion, and we want to have room for lots of honey.  This increases the
volume and ventillation requirements above what would otherwise be ideal,
but only for a short time during the expected flow. Thus the ideal
size/volume ratio is not stable. It varies with ambient temperature, and
of course bee populations expand as the daily ambient temperature rises.
 
As we can see, in marginal temperature and spatial conditions, the bees
fluctuate between occupying the whole hive and just the brood area.  Some
strains of bees tend to try to keep their stores near the brood
(occupied) area.  They don't care to store in remote areas, areas that
are only occasionally occupied by the bees. Cool hives may be a problem
if you are using them.
 
Once we leave the active season and look at the early spring and wintering
management, we see that these situations are normally at the low end of
the range of conditions discussed above.  Our goals and management
become very different when we start managing *inactive* bees.
 
High levels of activity are not desirable during those times and therefore
cooling the bees a bit with ventillation and encouraging clustering is
wise.  It keeps them home and conserves energy for later.  Ventillation is
also at such times necessary to carry away respiration products.  Since
insulation is often necessary to slow temperature fluctuations and reduce
chilling , increased ventillation also counteracts the resulting heat
retention and serves to help keep the bees clustered until there are
reasons for them to become active.
 
When time for the active season arrives, the observant beekeeper will try
to match the hive size and ventillation to the bees needs and the season.
She will be rewarded by healthier, more productive bees.
 
I hope this helps explain this concept better. It is one can make the
difference between success and failure.
 
Allen
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