> I think there is a misconception that hives are wrapped to help keep
> the cluster warmer or use less energy to keep itself from getting too
> cold. A little reflection will reveal that the bee colony is not in
> cluster a good part of the cold weather season. I don t know exactly the
> rate of BTU output that occurs during brood rearing but any one who has
> opened a hive on a cold or cool day (several factors involved) certainly
> can feel the warmth and it is certainly greater than the approximate 2
> BTU s needed to keep the cluster at it s desired temperature. I think
> most of us agree this figure is relative to the ambient temperature, ...
 
Good post, and one which reveals more understanding of the ways of bees
than statements based on simplistic steady state assumptions.
 
There is absolutely no doubt that wrapping is necessary where I keep bees.
 I've tried going without and the losses convinced me. That is not to say
that wrapping is required every year, but who knows which year will be a
killer?
 
Even if hives survive here without wrapping, careful tests have shown me
that the ones which were only insulated on top, and covered with plastic
on the sides do not yield as many spring splits as the ones that have at
least R5 on the sides.  We have been unable to see any advantage in going
beyond R5.
 
Having said all this, I must admit that there are a few around Edmonton
(north of here) who are able to winter successfully with no wrap other
than top insulation.  Personally I attribute that to the better
nutritional status of their bees due to their being in better pollen
areas.  Being more robust, their bees can stand more abuse by cold
weather.
 
Other than bees lacking good and sufficient feed in the late summer and
early fall, I find the main cause of winter loss is long cold spells in
February when temperatures may reach close to minus forty for a week or
more at a spell and be accompanied by strong winds at times. This stresses
the bees, since they are old and reduced in numbers and sitting on brood
which they attempt to maintain at 95 degrees F.  Since their food is by
then reduced in quantity and sometimes quality and sometimes receeding
from the cluster location -- which cannot move due to the brood -- the
bees are very vulnerable.
 
Wraps facilitate the use of any warm spells for relocation of stores.
When temperatures moderate at all after a cold spell, bees have been shown
to become immediately active.  At such times, they raise the interior
temperature somewhat and will rearrange their stores if they are able.
Some even take flights, even though the absolute temperatures are still
inappropriate in our view.  A little less heat loss will make a huge
difference at such times.
 
> New beekeepers ask me when should they remove the wraps, I suggest they
> leave them on until they feel compelled to get down into the lower
> supers.  I personally have found that early colony buildup is
> considerably enhanced with insulation wrap. I have no statistics but I
> believe evaporational cooling (wind drawing moisture through the wooden
> hive body) is an  unmeasured stress on brood rearing, especially early
> in the season.
 
This is a judgement call.  I've found that leaving wraps on too long can
lead to a lot of excess filght which can be a wasteful, and a nuisance
when there is nothing available to gather.  We unwrap beginning in late
March or early April to reduce flying and to facilitate working on the
 
 
bees.
 
>   If the heat can be conserved (insulation wrap) a number of benefits
> can be realized such as a)fewer bees to maintain proper brood
> temperature. b) conceivably a more brood and more rapid buildup. c)less
> honey stores for the brooding period (heat conversion).
 
Precisely.
 
If you are able to understand your bees, you have an opportunity to manage
here.  While I may want my bees to stay home, someone with abundant pollen
at that same time period might want to have the bees flying.
 
So I would unwrap.  (S)he wouldn't.
 
Allen
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