Our concern for moisture in winter??

[Grandpa Jim]

In the very beginning of the German videos "Beekeeping by Rotation System", hives are opened in winter and they have clear plastic covering the top of the frames inside the hive....no inner cover....no ventilation...no propped up cover...looks like the covers seal rather tight.  Is it the fact that they are using foam hives that makes all those things we do unnecessary?  I am sure they pictured their best hives, but those bees sure look dry and healthy.  We seem to do all we can to keep air flowing through our hives....with some keepers leaving screened bottoms open all winter.  Is there something we can learn here??

Jim

[BlueBee]

I’ve been using super insulated foam hives for a few years now.  Mine are homemade from 1” to 2” extruded polystyrene.  I’ve tried designs with top ventilation and hives with no top ventilation.  I never leave the screened bottom open in the winter.  The only times I’ve seen a moisture problem is when I didn’t have a proper drip edge on my top cover and water ran under the top and into the bees.  That generated a lot of mold and made a real mess.   

This winter I’m running my full sized hives with mid entrances (which become top entrances in the winter).  My nucs will all be running bottom entrances with a sheet of painters plastic for an inner cover; very similar to that German video.  I’ve run that way this summer and so far so good.

The main problem I see in highly insulated hives in the winter is overheating during a warm spell.  The bees make heat to keep the cluster warm and that does warm up a foam hive.  I’ve seen hives in the upper 80s when it’s 32F outside.  Problems start to occur if they get too hot in the middle of winter in Michigan.  The top vent/entrance in my full sized hives seems to prevent the excessive heat while still providing an insulating blanket for the bees.  Despite a common beek belief, a small hole in the top of an insulated hive is not going to let all the heat out.  Just like a small hole in the top of a human house doesn’t let all the heat out.

My nucs have less bees, generate less heat, and seem to do alright with just a bottom entrance and little or no top venting.  This winter, most nucs will get zero top ventilation.  They will have the plastic inner cover like the German video shows and yes, the bees seal that to the hive body thoroughly.

[BlueBee]

I suppose I should add that my full sized hives with the top entrance in winter do not have any bottom holes.  Hence there is not the opportunity for an easy convection current to set up and suck heat from the hive.   Heat will escape, but at a much slower rate since there is not an easy chimney effect in those hives.

In my nucs, I’m switching most over to derkem’s heat bubble approach this winter.  As in a bottom entrance and no top vents whatsoever.  Based on previous year’s observations, my main worry with the heat bubble approach is overheating.

[derekm]

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The main problem I see in highly insulated hives in the winter is overheating during a warm spell.  The bees make heat to keep the cluster warm and that does warm up a foam hive.  I’ve seen hives in the upper 80s when it’s 32F outside.  Problems start to occur if they get too hot in the middle of winter in Michigan.  The top vent/entrance in my full sized hives seems to prevent the excessive heat while still providing an insulating blanket for the bees.  Despite a common beek belief, a small hole in the top of an insulated hive is not going to let all the heat out.  Just like a small hole in the top of a human house doesn’t let all the heat out.

...

No they dont overheat.. had mine with a bottom entrance below floor level , no top entrance, elaborate sealing box to box,  no mesh,  levels of insulation  beyond yours Bluebee,

30C  in shade external temperature, hive in full sunshine no bearding.
The honey ripens quite fast though

If let them get on with their own style of Aircon they can control it themselves., when the only heat input is through the the entrance and their body heat