Beemaster's International Beekeeping Forum
BEEKEEPING LEARNING CENTER => GENERAL BEEKEEPING - MAIN POSTING FORUM. => Topic started by: BlueBee on December 06, 2012, 08:30:55 pm
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Anybody tired of talking about insulation? How about another much loved subject among bee keepers; ventilation. Surely beeks can reach a common ground on top vs bottom ventilation? Yes? No?
Yes, I know this has been brought up lots of times before but we’re not suppose to drag out old threads to append new observations, so I thought I would start a new tread on this topic.
I’m running hives and nucs with a variety of configurations this winter just to observe and learn. One thing that has really given me some new insight into winter behavior is the use of a plastic sheet/foil for an inner cover. Now I can watch the bees and the hive environment (temp, humidity, condensation, mold) all winter long without really disturbing the bees (except of course to throw in some more honey balls over the holidays ;)).
So here’s a couple photos from two hives. The first photo is from a hive with only a top entrance. Note, no condensation whatsoever. This design was totally dry and mold free last season too. The second photo is from a new hive with only a bottom entrance. Notice there is condensation in this hive, but the moisture is condensing to the sides of the cluster and I suspect won’t cause big problems; but time will tell. That situation changes if you super a poly box with a box full of just honey. Then the top box becomes cool and condensation occurs over the bees heads. Kind of gets back into that Derekm hive tread..... :-\
Based on the activity of the bees in each hive and my IR temp sensor readings, the hive with the bottom only entrance is warmer. That is not a surprise, but what does surprise me is the moisture seems to be under control at this point.
(http://i1082.photobucket.com/albums/j365/MichiganBee/Heat%20Measurements%20March24%202011/TopvsBottom1Dec6.jpg)
(http://i1082.photobucket.com/albums/j365/MichiganBee/Heat%20Measurements%20March24%202011/TopvsBottom2Dec6.jpg)
Thoughts?
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OK, I'll share my thoughts and conclusions on this subject. First, I believe that proper ventilation in the hive is what this all boils down to. Condensation any time is undesirable. The fact that brood and bees get wet during the winter will lead to premature death. The formation of mold is a secondary issue that I'm sure causes health issues for the bees. Secondly, a bottom entrance is needed to allow the bees to provide proper housekeeping. Where I live upper entrances give the bees a greater area to protect and can thereby allow pests like the SHB and wax moth to invade easier. I think that the answer might be to use a solid inner cover that has spacers on the edges like popsicle sticks and also use SBB with a fine mesh. This would provide adequate air flow for the hive to remain dry but not allow unwanted pests to attack the colony from multiple directions.
These are only my thoughts and rationalizations of the issues as I understand them.
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Thanks Ray. Those are some good thoughts. I don’t think there is such a thing as a right or wrong answer to the question of top vs bottom, so everybody should get an A in this exam. I can see pros and cons in both.
Do you leave your screened bottom open all winter?
I’m experimenting with a little of everything this winter to see how the different configurations will work here.
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I like the plastic topping and I think I will now have another use for my roll of shrink wrap. I have gone to an entrance bored in the top box right below the hand hold. Since I put a 2 1/2 inch feeder rim on top box, that is not quite a top entrance as a nearly 9 inch area above the entrance can collect heat and the bees do indeed stay pretty toasty in this configuration. Most of the bees seem to loaf hanging from the sound board innercover below the 1 1/2" styrofoam insulation once the cluster reaches the top and chews thru the mountain camp. I top insulate and my hive wrap is supposed to be R 3.7 Mainly it is a fine windbreak and dead air space. I close off the bottom entrance entirely for the cold months.
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Do you leave your screened bottom open all winter?
Right now I still have the full bottom SHB oil traps installed. The SHB can still be active at our current daytime temperatures and I don't want to take any chances. The high Sunday will be near 80degF. When and if we ever see consistent temps below 50degF I will be installing the SBB. I have the normal solid inner covers with a top entrance. I have modified them so that the entrance has fine mesh screen stapled over it and the regular oval hole is 4" in diameter so the bees can better access the bucket feeder holes.
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Can some one will give a typical size and placing for a top entrance, so i can put together an experiment to measure heat loss?
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And to think I thought this subject was about something entirely different! :-D
...DOUG
KD4MOJ
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Size and place of a top entrance?
Well, it’s at the top. :-D Sorry, I couldn’t resist.
For winter I reduce my top entrances down to 9mm x approx 50mm. My top entrance is actually 60mm below the very top.
The bees have done great in those hives, but I've only been able to guess what the real temperature is inside. At least with my clear plastic inner covers I can now get a better sense of how the bees are responding by observing how tight or loose the cluster is.
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Wonderful discussion. We are waiting on BlueBees results for sure. Seems there are a lot of experimenter Beeks trying to determine pro and con on this issue. For my bees I'm convinced Top entrances have saved them from certain doom due to condensation. That said I still use bottom enrances (set at smallest opening in winter) for all but 2 colonies (out of eight) this year.
My top entrances are simply a notch cut into the bottom of my inner covers, allowing the hive to expand w/ the bees.
Those plastic sheets look interesting, I believe I've seen them used by some German Beeks with good success. What are they? Just plastic, any kind of plastic. Very cool 8-)
Thanks for another great post BlueBee.
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there is an example of plastic being used in this clip. these hives in general are interesting
www.youtube.com/watch?v=gKTvp1lupHY (http://www.youtube.com/watch?v=gKTvp1lupHY#) - Cached
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Rober, yep that is the video I got the idea from for my plastic sheet/foil inner cover. Lots of good bee keeping nuggets in that video IMO.
Here’s a photo from earlier today of the 6 frame medium nuc that is configured with only a small bottom entrance (9mm x about 120mm). This hive is definitely on the warmer side since the bees aren’t in a tight cluster. They are just milling around inside the hive. Temps look great in here, but the condensation is getting a little worse. Still not like the rainy season in Florida, but clouds are forming.....
(http://i1082.photobucket.com/albums/j365/MichiganBee/Hive%20Venting/TopvsBottomDec11.jpg)
The interesting thing I see here is the condensation is off to the sides of the hive and away from the bees in the SINGLE DECKER nucs. So if the condensation gets big enough to start raining down, at least it won’t fall on the bees. The condensation in my double decker foam nucs is forming ABOVE the bees heads in the top box. This is more likely to be a problem since at some point it will eventually rain down on the cluster. If the volume of the foam is 2x the size of the cluster, the upper layer of combs are getting cold and looks to be cooler than the dew point inside the hive.
The hives with top entrances/vents basically look exactly like the earlier photo. Bone dry and the bees in formal cluster. They’re not moving around a whole lot, but they're not frozen stiff either. Looks to be “sleeping” as Finski would say.
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I like the idea you have shown with the plastic. Looks to be especially valuable to check on stores and/or emergency feeding.
I currently use both top and bottom entrance. Bottom in most hives are left open this year except for 1/4" screening as mouse guards. The top entrance it the usual opening in the inner cover.
Obviously if I plan on using the plastic I would need to modify how the inner cover is placed. Probably replace with a shim to incorporate an entrance and plastic.
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The hives in the videos do not have a top entrance as far as I can tell. What they do have is an completely open bottom that the bees use for an entrance and to feed from the metal bowls. I always thought that the vis-queen covers trapped too much moisture. Maybe I'm wrong and the whole hive bottom open vents it out? She sure throws those hive bodies around, doesn't she.
By the way, all my inner covers have the notch down in winter. Bad experiences without a upper vent hole in winter for me.
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For a hobbyist like myself, I really like the plastic inner cover. It allows me to watch the bees and monitor how my different homemade hive designs are performing. To date I haven’t had the need to feed any of my hives (except for the mating nucs in that other thread), but the plastic cover really works great for adding in some emergency food. You can just peel it back a ways and put in food with minimum disturbance to the bees.
Good point Tefer, the plastic would interfere with vapor that would normally escape through an inner cover if that is your configuration. The usefulness of the plastic inner cover is going to be dependent upon your hive venting design.
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Interestingly, you may recall seeing the condensation in one of my mating nucs with a top entrance in that other thread. Here is the photo again:
(http://i1082.photobucket.com/albums/j365/MichiganBee/Queen%20Bees/MatingNuc2Dec12.jpg)
That seems like some pretty significant condensation and that is with a top entrance! Go figure. You can kind of imagine the convection currents in that photo as the warmer air rises above the bees and circulates to the edges of the box where the condensation is occurring.
It is curious how I’ve got all this condensation in my mating nuc with with a top entrance but NONE in the full sized hive with a LOT more bees (beach ball sized clusters). :? I'm not sure how to explain that at this point.
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BlueBee, I have a question about top entrances. How do the bees clean out the hive debris and dead. I see a lot of experienced beekeepers who swear by top entrances I just don't understand how the bees deal with the housekeeping issues.
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Anybody tired of talking about insulation? How about another much loved subject among bee keepers; ventilation. Surely beeks can reach a common ground on top vs bottom ventilation? Yes? No?
I'd say no ...
My reasoning is that there may be 2 different mechanisms at work. Don't ask me exactly what they are - I just know that 2 conflicting dynamics are involved.
My evidence for saying this ? Observations.
Take clouds for example. They are evidence of suspended moisture, which has become visible by virtue of warm air containing that moisture rising up from sea-level and reaching the coldness of altitude. If that moisture should then become even colder, such as happens when the supporting air is forced to rise up over a mountain range, even more moisture will come out of suspension, and precipitate as rain (or snow if it's REALLY cold).
Ok - so far so good, no surprises there then.
Now lets take another scenario with this warm air containing moisture: when a belt of warm air (with it's suspended moisture) hits a cold front, then fog results, as the moisture comes out of suspension. Same principle, with humid air revealing the moisture it's carrying as a direct result of it suddenly becoming cold.
What we are witnessing are clouds of moisture occurring at high level, and clouds of moisture occurring at low level. One event taking place at high altitude (a dynamic which supports the upper entrance theory), but the other taking place near ground level (a dynamic supporting the bottom entrance theory).
Both events take place in the natural world - what is needed (imo) is for someone knowledgeable about such things to explain the conditions where one occurs and not the other - which may possibly go some way to solving this seemingly never-ending conundrum.
LJ
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I think I've got it ...
It's all to do with the weight of the water, and the temperature (lifting capacity etc) of the air.
Modest concentrations of moisture can easily be lifted by warm air.
But dense concentrations of water vapour (heavy ...) held by not so warm air, will be unable to rise, and thus will stay close to the ground.
That's why this conundrum can never be solved - because 'it all depends'. Looks like both entrance locations will work, albeit under different conditions.
LJ
(any physicists in the house ? confirmation of the above required)
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I am still a newbee, last winter was my first and it was fairly warm. I had SBB, bottom entrances, an inner cover with hole in middle and a gap on each side with a telescoping cover. They did fine, I do have my hives on a slab with chain link fence around it with a small doorway on the south side, it also has a roof. I put plastic sheeting on the west and north sides. This fall I had some robbing and closed the entrances to about 3 in wide. I also last year and this duct taped over the side holes in the inner cover except on the south side. I am a lot farther south than a lot of you. The hives normally don't get wet when it rains unless it blows pretty good. Good luck to you.
Joe
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Water vapor has a specific gravity of 0.6218. That's 1 third lighter than air which has a specific gravity of 1.000.
http://www.engineeringtoolbox.com/specific-gravities-gases-d_334.html (http://www.engineeringtoolbox.com/specific-gravities-gases-d_334.html)
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Water vapor has a specific gravity of 0.6218. That's 1 third lighter than air which has a specific gravity of 1.000.
http://www.engineeringtoolbox.com/specific-gravities-gases-d_334.html (http://www.engineeringtoolbox.com/specific-gravities-gases-d_334.html)
Yep - I found that out just this morning. Got the following from a hot-air ballooning site:
Moist Air - In the real world the air always contains some moisture. The addition of water vapour to a mass of air makes it less dense. Whilst this may appear a bit odd at first this occurs because the molecular mass of water (18) is less than the molecular mass of air (29).
It seems that in life sometimes it's necessary to stick your neck out and get something wrong, in order to learn from that mistake.
What you write is true - moisture-laden air is LESS dense than dry air, and thus will rise. Even the Wiki on this (http://en.wikipedia.org/wiki/Density_of_air (http://en.wikipedia.org/wiki/Density_of_air)) describes it as 'counter-intuitive'. Indeed, just about everybody I know who uses bottom entrances - including myself - does so in the belief that moisture-laden air is heavier, and thus will fall to the bottom of the hive and exit.
The only explanation I can offer for this confusion comes from the oft-quoted paper by Thur, who recommends the idea of 'upper integrity' (my words) thus implying that entrances should only be at the bottom of the hive. He writes:
Only the used air of respiration drops downwards, laden with carbon dioxide, and at the open bottom margins of the comb it is exchanged with fresh circulating air. .
CO2 of course has a molecular weight of 44, which will make air containing it heavier - but the same air will also contain water moisture, making it lighter.
Looks like it's time to get the calculator out ...
'best
LJ
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... Indeed, just about everybody I know who uses bottom entrances - including myself - does so in the belief that moisture-laden air is heavier, and thus will fall to the bottom of the hive and exit.
The only explanation I can offer for this confusion comes from the oft-quoted paper by Thur, who recommends the idea of 'upper integrity' (my words) thus implying that entrances should only be at the bottom of the hive. He writes:
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The issue is people jump on a single facet of a conclusion without understanding what is beneath it and then try to apply that conclusion to circumstances where it doesnt apply.
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My 2 cents worth. I use an inner cover year round. I take a saw and cut the lip on one end. Take out a chunk so I have an opening about 1 in. wide and 3/16ths deep. I turn them with hole down in winter and up in summer. Works great.
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>The issue is people jump on a single facet of a conclusion without understanding what is beneath it and then try to apply that conclusion to circumstances where it doesnt apply.
Or it applies only somewhat. Reality is not just one simple measurable thing, but a complexity of things. In this discussion we have brought out that CO2 is heavier than air and water vapor is lighter than air. Which wins out?
There are many things like this where what we think is the measurement for something is only one aspect of it. Which would you prefer, a sunny calm, dry, 10 F day or a blowing, humid, rainy 40 F day? You'll be warmer when it's 10F, sunny and calm even though we think temperature is how you measure cold...
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... even though we think temperature is how you measure cold...
That is exactly the wooly thinking I'm talking about which has "Damp kills bees not cold" as one of its sayings
Heat flow confused with temperature.
And the Co2 vs H20 question is in the same trap
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Just found an interesting idea - from:
http://www.uoguelph.ca/canpolin/Publications/ThompsonCody_MSc2011_edited.pdf (http://www.uoguelph.ca/canpolin/Publications/ThompsonCody_MSc2011_edited.pdf)
The thesis itself is a tad disappointing from a practical beekeeping point-of-view, in that nothing definitive emerges - but there is some confirmation that having a cavity beneath a bottom entrance (which I interpret as being the same as raising the bottom entrance a few inches) may be a beneficial strategy. Something to do with a vortex being created around or near the entrance.
The bloke goes into some pretty hairy maths: fluid dynamics, boundary layers, that kind of thing - the sort of stuff usually applied to modelling jet aircraft wings - I only hope that bees appreciate how scientifically advanced they are :) - but it may be worth mentioning that the original idea for this thesis came from someone's intuitive beekeeping practices.
LJ
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Here’s an update on my top vs bottom entrance winter study. Photos taken today about 3pm. We’ve had an extended period of seasonably cold weather here in Michigan and virtually no sun. A couple of nights down to single digits and no days above freezing. The kind of weather that takes out hives.
(http://i1082.photobucket.com/albums/j365/MichiganBee/Hive%20Venting/TopvsBottom5framemedium5Jan13_zpscc7d0242.jpg)
(http://i1082.photobucket.com/albums/j365/MichiganBee/Hive%20Venting/TopvsBottom5framedouble5Jan13_zps7bbfb524.jpg)
(http://i1082.photobucket.com/albums/j365/MichiganBee/Hive%20Venting/TopvsBottom8framemedium5Jan13_zps8d5cfa8d.jpg)
(http://i1082.photobucket.com/albums/j365/MichiganBee/Hive%20Venting/TopVsBottomJumbo5Jan13_zpsbc8cffb8.jpg)
My hives with the heat bubble designs (only a bottom entrance) show LOTS of condensation and my hives with a top entrance show virtually none. My observations of bee activity in the various designs (I have plastic tops to watch them) lead me to believe the heat bubble designs are indeed a bit warmer (as theory suggest). However when I weight the risk of cold vs wet on the bees, I think wet is a much more deadly threat.
If we ever get back above freezing here, I might go out with the drill and make some mods to a couple of my heat bubble designs to see if I can’t improve the condensation problems.
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How big are your entrances, and do you have any other ventilation other than the entrances?
mvh edward :-P
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Edward, I’m experimenting with a few different configurations this winter but each hive has either a bottom entrance or a top entrance; never both. No top vents with bottom entrances.
If there is a entrance on the bottom and a hole at the top, you’re going to create a convection current (chimney effect) right through the hive which is going to make it simpler for heat to escape. That defeats the value of insulation to some degree. Probably doesn’t make a bit of difference in most American wood hives since they have virtually 0 insulation value to begin with. However a convection current could put my 38mm of polystyrene to waste! I sure don’t want that to happen; so no chimney effects in my hives. :)
Most of my hives have entrances that are about 9mm tall by 75mm (3”) to 100mm (4”). I didn’t want to close them down too much for fear of trapping too much CO2 inside. On the big hives, the bees chew out the entrance reducers.
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So if I understand it your entrances are 9mm high and 75-100mm wide ?, no other ventilation?
And either top or bottom placement, with no other ventilation?
mvh edward :-P
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That is correct.
My goal is to inhibit the loss of heat via air infiltration while at the same time allowing for sufficient exchange of gases. I'm not claiming I'm doing it right, mind you! I'm just reporting what my goal is. :-D
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OK, what are your highs and lows in winter temperatures and how long is your winter, or how long do the bees not fly out of the hive.
mvh edward :-P
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Michigan is located near the middle of North America and as such we have a continental weather pattern. In the winter, cold air from Canada normally dominates our weather, but we usually do get breaks in the cold if high pressure set up on the east coast and pushes warm air from the Gulf of Mexico up this far north. First freeze is typically Oct 15th. Last frost is typically early May. Looks like our temps have been a little cooler than Helsinki lately.
Because our weather is so variable, it is hard to predict how often the bees can make a cleansing flight. I would say it would be rare for the bees to be cooped up for more than 3 solid months without a cleansing flight. Spring doesn’t really start to arrive here until Mid April.
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Ok that about what I have were I live in Sweden.
The way I and many others keep our bees in poly hives is with no ventilation in the top and ventilate with a metal screen over 70% of the bottom and an open entrance that wont allow mice to crawl in.
I myself and many other have a Swedish raised bottom board called universalbotten http://www.pixonia.com/universalbotten2011.pdf (http://www.pixonia.com/universalbotten2011.pdf) It has a metal ventilation grid in the rear that works like the back wall of your fridge and attracts moisture.
The front entrance is also open so air can flow freely across the bottom so the moisture ventilates out.
In the winter time with freezing temperatures the air is often very dry and helps keep hives dry.
None of my hives have the amount of condensation I have seen in your pictures and never over the hibernating bees, eventually a little moisture or frost on the outer skirts of the ball of bees.
All though I haven't looked at them on a continual basis under the whole winter. Just now and then in extreme causes.
In a nut shell our hives have a warm winter cap and a drafty floor to get rid of moisture, the walls may bee wet with condensation that run down and out of the hive.
This is just info on how most of us do it here :)
Hope you learn a lot with your experiments and they work out, if not you have some more ideas to play with next winter ;)
mvh edward :-P
PS if the link doesn't work you can google " universalbotten " and look at the pdf file or google pictures and you can see the different bottom types.
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Also your condensation could be from the limited ventilation or the small nucs have a hard time keeping the hive warm.
mvh edward :-P
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Thanks for the ideas Edward. I do have 4 nucs with open bottoms in my bag of experiments too. 2 are now dead. The other 2 had a bunch of dead bees under them the last time I checked (not a good sign), but they were still alive.
I liked the theory behind the “heat bubble” design that Derekm is fond of, and I wanted to experiment with various versions of that this winter. If the condensation problem could be solved, that should be the most energy efficient design there is.
I’m not real comfortable with the idea of an open bottom due to thermal reasons. Do houses in Sweden have crawl spaces or basements? A lack of insulation underfoot makes for a cool room! I’m not saying it doesn’t work overall; I just don’t like the idea of wasting heat. However if it comes down to wasting heat vs a cold shower for the bees, I’ll go with wasting heat.
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very interesting and well said Edward, Blue Bee I have a hive with glass sides that illustrates Edwards descriptions I'll post, the condensation line stays below the cluster assuming they have the bodies to generate the heat to push the cold down that low
Cheers,
Drew
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That would be interesting to see.
Unfortunately my hives are not instrumented so I don’t know exactly what the temperature profiles inside are, but based on the condensation I’m observing, it’s pretty clear (at least in my hives) that the top comb temps in a double decker is below the dew point and no matter what I do in that design water is going to condense over the bees heads. I could probably at 100mm foam on top of the double deckers and it wouldn’t make a bit of difference. When the bees are in the bottom box, those top combs are not going to be real warm.
In my hives wintering in a single box, it might be possible to get the condensation to move over to the side walls as you suggest Drew. It’s almost there already.
Where the condensation forms is going to depend upon how warm your hive is in the first place (insulation value) and where your bees are located (top vs bottom box). If the upper part of your hive is warm enough (above the dew point), then you would not have condensation up there. My 8 frame nuc (with all the water you can see in the photo) has 38mm thick foam walls. The odds are that nuc is better insulated than 97% of beeks in North America. So if I’m getting condensation without a top vent, the odds are everybody else is too. :)
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Thanks for the ideas Edward. I do have 4 nucs with open bottoms in my bag of experiments too. 2 are now dead. The other 2 had a bunch of dead bees under them the last time I checked (not a good sign), but they were still alive.
I liked the theory behind the “heat bubble” design that Derekm is fond of, and I wanted to experiment with various versions of that this winter. If the condensation problem could be solved, that should be the most energy efficient design there is.
I’m not real comfortable with the idea of an open bottom due to thermal reasons. Do houses in Sweden have crawl spaces or basements? A lack of insulation underfoot makes for a cool room! I’m not saying it doesn’t work overall; I just don’t like the idea of wasting heat. However if it comes down to wasting heat vs a cold shower for the bees, I’ll go with wasting heat.
if your hive is insulated the condensate will not be much colder than the dew point. the dew point is likely to be high not low ... Condensation does not necessarily mean cold....jus a surface lower in temp than than the dew point. Condensation inside the hive rather than outside means heat gain to the hive rather than heat loss.
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Thanks for the ideas Edward. I do have 4 nucs with open bottoms in my bag of experiments too. 2 are now dead. The other 2 had a bunch of dead bees under them the last time I checked (not a good sign), but they were still alive.
I liked the theory behind the “heat bubble” design that Derekm is fond of, and I wanted to experiment with various versions of that this winter. If the condensation problem could be solved, that should be the most energy efficient design there is.
I’m not real comfortable with the idea of an open bottom due to thermal reasons. Do houses in Sweden have crawl spaces or basements? A lack of insulation underfoot makes for a cool room! I’m not saying it doesn’t work overall; I just don’t like the idea of wasting heat. However if it comes down to wasting heat vs a cold shower for the bees, I’ll go with wasting heat.
if your hive is insulated the condensate will not be much colder than the dew point. the dew point is likely to be high not low ... Condensation does not necessarily mean cold....jus a surface lower in temp than than the dew point. Condensation inside the hive rather than outside means heat gain to the hive rather than heat loss.
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I liked the theory behind the “heat bubble” design that Derekm is fond of, and I wanted to experiment with various versions of that this winter. If the condensation problem could be solved, that should be the most energy efficient design there is. I’m not real comfortable with the idea of an open bottom due to thermal reasons. A lack of insulation underfoot makes for a cool room! However if it comes down to wasting heat vs a cold shower for the bees, I’ll go with wasting heat.
Yes I know what I have written doesn't seem to make sens, and I had a hard time understanding it in the beginning.
How could cold floors bee a good thing in the winter time, surely it would bee better with warm bees in the winter.?
The biggest problem for the bees in the winter is getting rid of excess moisture and condensation .
I think the whole idea with poly vs wood is that the poly hives are easier for the bees to maintain a constant temperature.
Because of the insulation the bees don’t have to work as hard to keep a warm stable temperature, this means that they use less honey/sugar supplies throughout the winter. If the eat less there bowls will bee not as full and they wont poop inside the hive.
Small or week hives can bee help through the winter if they are kept in a place were the temperature, humidity are constant and they are not in a draft, a shed,barn, garage, or some quiet location.
All hive should bee of the ground, 20-40cm to escape damp and cold radiating from the ground.
Also the poly hives stop both heat and cold radiating into the hive, like a cold draught from a window in winter.
General drift forms for my hives are;
Winter, open with draft over the floor to vent moisture
Spring, after cleansing flight close the ventilation with a small front opening, this helps them keep the brood warm as the old bees die off and before new bees hatch.
Summer, open ventilation so they can cool the hive and dry nectar to honey
Fall, depends on feeding and how late, early, open so the can dry winter stores, late, closed so they can keep warm, make wax to cap cells.
If you have a hot hive that has brood late in the fall opening the ventilation and cooling the hive will help stop the brood cycle.
If you miss closing the ventilation in the spring the hive will not preform well, very important to get an early build up.
mvh edward :-P
All the old beekeepers fight but one thing they all agree on is the cold is not a problem for any normal hive with stores, but wet bees are not happy and will bee cold dead bees.
Ps yes we insulate our floors in our houses. :-D
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Condensation inside the hive rather than outside means heat gain to the hive rather than heat loss.
Aaaahh… a very good point that I kind of forgot about.
You know the single layer nucs with the heat bubble design has the condensation forming away from the cluster of bees, so I suspect if I stick with a single box design, the condensation won’t really do any harm to the bees. I will keep some of nucs with this design exactly as they are. I think I will do a little experimenting with a couple others to try to change where the condensation is occurring.
How many watts are we gaining by letting water vapor condense inside the hive?
Edward, thanks for explaining your setup. That is very interesting. BTW....too often our floors are NOT insulated!
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I have considered whether a slanted ceiling would be advantageous
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I have considered whether a slanted ceiling would be advantageous
I try to make sure my hive all lean slightly towards the entrance or back ventilation to make sure the wet damp will drain out of the hives and not cause a pool of water. It might also benefit the roof.
mvh edward :-P
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Condensation inside the hive rather than outside means heat gain to the hive rather than heat loss.
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How many watts are we gaining by letting water vapor condense inside the hive?
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you get back about 10% of the heat expenditure
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I haven’t observed the bees lapping up any of that condensation yet, but I’m not watching 24-7 either.
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I haven’t observed the bees lapping up any of that condensation yet
They probably only do that if they have larvae to feed by mixing pollen and honey to make feed juice .
mvh edward :-P
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That makes sense Edward and matches what I have observed. Namely bees collecting lots of water when raising brood.
But over winter when they are broodless, do you think they dilute their honey at all for personal consumption, or do they just consume it raw?
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Less water, less poop :roll:
mvh edward :-P
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I have considered whether a slanted ceiling would be advantageous
Or fit a moisture condensor ? (pipe the trough out through the side)
(http://i46.tinypic.com/2m84f9z.jpg)
LJ
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interesting design, I don't hold that it is advantageous for moisture to condense @ the top, I consider it a sign of inadequate insulation.
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In theory I agree with you Drew. But what I have seen in my hives is you can’t really add enough insulation to keep water from condensing above the bees IF your hive is a 2 story. That second story just gets too cold (below the dew point) and you get condensation no matter what you do (unless you vent the top). The weird thing is double deckers seem to be recommended configuration for wintering bees in the north.
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Even were I to concede your point, it would, to me, suggest another problem :
-hive not airtight
-entrance to big
-cluster to small
another thought : -hive shape
hand to forehead thought - vertical distance cluster to entrance, add empty ?
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I’m not the type of beek who believes in absolutes, but I can tell you my latest heat bubble design is about as air tight as possible! It’s basically a box under a foam shell. The foam shell is completely airtight since it was glued together with gorilla glue. I could use it for a boat if I turned it upside down. So it's very air tight.
Next concern: entrance too big? My entrance is 9mm x about 100mm, even smaller on some boxes. Any smaller and I fear the bees would be asphyxiated due to a lack of O2/CO2 exchange.
Next concern: Cluster too small. That could be. It is pretty clear when looking at hives through clear covers, that a small cluster in an insulated box acts as an ice cooler. That can’t be good for the bees or condensation. You need appropriate sized cluster for the size of the insulated box.
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lets see.......you haven't created a bubble, got to add height, or decrease width,increase insulation, is this a nuc we are talking about I forgot :) 2" on top sounds thin, I have 1" pvc entrance I believe to be more than substantial enough.... TBC :)
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LOL....2" of foam sounds thin? How many inches of foam are you using? The thickest stuff they sell here in the big box stores is 2" thick.
I don't think are friends in Scandinavia even have 2" (50mm) thick insulation in their hives. :)
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better to say your bubble is getting constantly irritated by entrance air, it needs static, and my 1" pvc is half blocked
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Or fit a moisture condensor ? (pipe the trough out through the side)
(http://i46.tinypic.com/2m84f9z.jpg)
LJ
Never seen like that.
First what I think is that that in that construction a hive looses kits valuable heat to the loft.
What is the advantage of that? - I cannot see any advantage.
When you feed the hive for winter, make it quickly that bees do not start brood rearing and they return to autumn rest mode as quick as possible.
Bees must be in winter mode that they do not consume their inside body stores (fat body). When nature gives pollen, it is time to wake up.
in Finland as in Michigan bees should be now in winter cluster. And it is not a bad thing in UK either.
To keep bees in wake up mode during winter is very strange. It tells only about nervous beekeeper.
When you feed your hives full in autumn, food stores cannot cease in couple of months. If the hive makes brood all the winter around, that is a bad thing too because in Michigan level it is sign of "non locally adapted strain".
in UK many places gives pollen in January and temp is +10C.
But I cannot understand why to feed hives in January? At least, if I give emergency feeding to my hives, I pour
syrup into combs. Easier way is to take a crystallized honey frame from store house.
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better to say your bubble is getting constantly irritated by entrance air, it needs static, and my 1" pvc is half blocked
That is a legitimate concern and I have addressed that in more recent designs by using an entrance "tunnel" as opposed to a 9mm x 100 gap. My entrance tunnels are now about 100mm long and should buffer the wind considerably. Your PVC is probably also a good idea. I considered using PVC pipe, but I thought the bees could defend a 9mm tall tunnel better than they could defend a pipe so I went the tunnel route. Defending against robbers and yellow jackets that is. I still like the idea of low cost PVC though.
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in Finland as in Michigan bees should be now in winter cluster. And it is not a bad thing in UK either.
Do you mean sleep like this?
(http://i1082.photobucket.com/albums/j365/MichiganBee/Extra%20Deep%20Hives/JumboJan11_zps6045344a.jpg)
I’m just joking with you Finski. You are right, sleep is good, but we are enjoying a record heat wave for a couple of days here and most of my hives were out in mass today. There were so many bees flying around it sounded like there was a swarm in the air.
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Yes we are enjoying record heat here in Michigan and MOST of my bees are out taking advantage of the warmth. All my wood hives (bottom entrances) and all my top entrance foam hives were active today. What were not active were my double decker foam hives with just a bottom entrance. They respond MUCH more slowly to the environment and I feel that is a negative of that design. I also find much more condensation over the bees heads in those designs.
(For the record most of my hives are foam, I only have about 4 colonies in wood. The one good thing about wood is IF they survive the cold nights, they do warm up nicely on days like this).
Here’s a photo from today of a 4 frame medium nuc using the heat bubble design. Lots of condensation AROUND the bees, but the colony looks pretty healthy to me. If this were a double decker, all that condensation would be on the combs over their heads.
(http://i1082.photobucket.com/albums/j365/MichiganBee/Hive%20Venting/mediumnucJan11_zpsd57db1ea.jpg)
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If you cut the wet ends off that hive, around cluster, (decrease, I assume depth), what would the pic look like ? In other words... the middle is dry, if you were to peel off that side I think you would see the condensation in a U pattern. Yes ?
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That would be a good guess, but I don’t know. I’ll have to take a closer look tomorrow. More record heat tomorrow :)(Saturday) before reality sets back in. :(
I suspect if there were more bees in that box or the box was smaller the zone of condensation would be pushed down onto the end walls. As you can see from my various photos, that condensation pattern repeats itself over and over in my heat bubble nucs.
It will be interesting to see what happens to the condensation as we get into February and March and the bees start brooding. Who knows, maybe the bees will start licking up some of that water?
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I believe that clue is a vitally significant one that was missed by Langstroth and everyone since. They didn't understand/comprehend significance of it, just as you are missing it, as did I :) They didn't understand thermocline layer. Look again..... think in 3D, the VERTICAL pattern of condensation. When you....admit?:) that if you squeezed in those ends the, "zone of condensation", must go down, then you have got the thing ! When executed properly no condensation will occur above top of bottom entrance.
p.s. more insulation, better seal, airtight critical
p.s.s Natures distillery :)
Last one :) If you go back, re-read Langsroth, Huber, the clues are there,they saw it, just like you and I, they missed the significance.
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Kind of interesting looking at the condensation patterns again today. I put my hand on the combs today and some are starting to heat up. The big hives were downright hot (top vents). I assume they might be starting some brood. The condensation in a couple of the single layer heat bubble nucs has disappeared (not so in the double deckers). I don't know if that's because the temperature in the hive went up (and the condensation went back to vapor) or if the bees could be lapping some water up.
You make some good points Drew. I think the optimal hive though is a combination of the hive's thermal characteristics AND the volume of the bees inside. If either one of those is not right, you get condensation where you don't want it. Even the perfect hive design is going to disappoint if you don't have a big enough volume of bees.
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I don't know about perfect, but an improved hive design would......insure, the beekeepers control of thermocline/that the B's were always able to maintain a thermocline, below their cluster. And yes, when the heat goes up the thermocline decends.
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I've just found a webpage which may have some interest for those seeking to deal with the condensation vs heat loss trade-off: http://letok.narod.ru/zima.htm (http://letok.narod.ru/zima.htm)
Google does a reasonable job of translation, but if there any Russian speakers out there, there are a few words which could benefit from being tidied up !
Basically, what the guy has done now for 2 winters, is to completely seal the top of the hive using a layer of medium-thick polyethylene sheeting, with a thin layer (3mm) of polyethylene foam over. This is kept in place by means of an oversized eke, which holds the poly and foam in place in the same way as a drumhead is held down onto a drum by a rim. This combination allows the poly sheet to remain cold enough for water to condense on it's under side.
Then - and this is the simple but ingenious bit - he simply places a length of 2x2 under one side of the hive to allow the condensate to trickle down one of the walls.
I'm fast coming to the conclusion that there will always be a trade-off between moisture removal, and the amount of heat retention preserved - that is, unless/until some genius comes up with a really clever ground-breaking idea.
Later ...
I've just realised that there are 2 sheets of polyethylene involved (dodgy translation ...), and this is how I visualise this system operating:
(http://i49.tinypic.com/2uol0md.jpg)
Black lines being the polythene, and the red line being the foam. Moist air escapes through the gap in the lower barrier, only to condense on the upper barrier. Condensate then runs down along the polythene sheet, down the inside front wall of the hive, and exits via the entrance slot.
LJ
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That’s an interesting design LJ.
As this point, I don’t think the condensation in my single layer heat bubble designs is going to be detrimental to the bees since winter is about half over and almost all the condensation is away from the bee cluster. The only potential problem I see with my polyethylene sheeting is the condensate running down the sheeting in the wrong direction if it is not taught.
Your post did give me another idea. If I replaced my polyethylene sheet with double walled polycarbonate (greenhouse glazing), I might be able to get the condensation to form inside the polycarbonate cavities. That might be a little more insurance against drips on the bees, but I don’t know if it would warrant the extra costs.
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Remember any devise designed to condense water vapor, does so at expense of heat.
p.s. In which direction would you surmise Apis might prefer to,......discharge, heat ?
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What I think doesn't matter, and with respect, what you think doesn't matter.
What matters are what conditions bees consider important criteria within their preferential home.
Tom Seeley often says "If in doubt, ask the bees."
So - what I would suggest is an experimental setup: a swarm of bees held within a very small central box which is connected to two identical hives by wide tubes - in a kind of 'two-wing' arrangement. Or perhaps - simply a swarm offered the choice of two empty hives.
One of these hives would be maintained warm, but damp; the other maintained somewhat cooler, but dry - then wait and see which set of conditions the bees select as being suitable for their home.
It may be necessary to run such an experiment multiple times in order to demonstrate validity, but my money would be on the bees making a definite choice. This would be a tad better approach methinks, than human beings trying to second-guess what conditions bees prefer ?
LJ
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Would not a glass hive, w/ horizontal plane, defined by line of condensation, do the trick ?
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I will say this; you’re persistent ;)
The photos on this thread make it pretty clear that if condensation is a primary concern, that is easily solved with a top vent. If you’re concerned about losing 10% of the bees heat due to heat escaping with the water vapor, then maybe adding some solar gain to your design would be a good idea.
Bees aren’t generating many watts in the first place; just 10s of watts at best. If you’re losing 10% with escaping water vapor, we’re only talking a couple of watts! A couple of watts isn’t diddly squat compared to solar gain. Solar gain can be about 100 watts per square foot.
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If you’re concerned about losing 10% of the bees heat due to heat escaping with the water vapor,
To where you may loose hive energy:
- too much room for colony
- poor insulation
- windy site of hive
- feeding hole open/chimey effect
- mesh floor ventilation/ ( solid bottom has only 5% opening compared to MF)
- hive continues brooding
- beekeeper disturbes the hive very often and wake up from winter sleep with his honey balls and thanks giving presents
- knock knock, are you alive
.
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I will say this; you’re persistent ;)
The photos on this thread make it pretty clear that if condensation is a primary concern, that is easily solved with a top vent. If you’re concerned about losing 10% of the bees heat due to heat escaping with the water vapor, then maybe adding some solar gain to your design would be a good idea.
Bees aren’t generating many watts in the first place; just 10s of watts at best. If you’re losing 10% with escaping water vapor, we’re only talking a couple of watts! A couple of watts isn’t diddly squat compared to solar gain. Solar gain can be about 100 watts per square foot.
solar gain in winter is a myth, that appears at10am and is gone by 3pm( with the usual bee hive surfaces). You loose more during the night. Large swings in hive temperature is all you get, but no net gain by the time the sun comes out on the 2nd day.
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Agreed. But if you add a solar input to your hive WITHOUT degrading the insulation value, then I suspect you can get a significant net gain. There is plenty of mass inside a hive to absorb heat during the day and to release it during the night.
For example, say you put photovoltaic cells on the outside surface of your hive and fed the electrical power from those through two small wires into a power resistor inside the hive. In that implementation you haven’t degraded the insulation of the hive and you have added some extra wattage inside the hive which it would not normally have.
Photovoltaic is not the way I would go because it’s too inefficient. I just used that as an example since it could clearly be implemented without altering the insulation value of a hive.
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First time using foam shells around my hives this winter. As of last week (w/temps in the low 40'sF) all 8 colonies are alive.
However, we're getting 20 below zero this weekend.. Kill them cut worms, kill them slugs, freeze the lakes..... 8-)
One observation so far; all hives w/ 'both a top and bottom' entrance still open (one or two beespace size) have some frost at the top entrances on colder mornings.
I have two w/ just top entrances (and a LONG Hive) and they have not experienced this "new" (to me) frost phenomena.
Any ideas?
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I have always wondered why some BK wrap there hives in black tar paper??
I can understand the wind shielding aspect, but heating the hive on sunny winter days will cause the ball of bees to break prematurely and result in a higher consumption of winter stores.
Studies that I read show that a steady constant hive temperature makes things easier for the bees to maintain a warm bee ball in wintertime.
The bees need a quiet stable environment.
mvh edward :-P
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One reason beeks wrap hives in tar paper is because the bee keeping books here tell us to!
Most hives here are also 19mm thick wood hives. Since there is virtually 0 insulation value in such thin wood, the hives most people use are going to cycle from the low of the day to the high of the day. So there is already a lot of undesirable temperature cycling. Worst yet, if it dips down to -20F/-28C at night, those wood hives fall to -20F/-28C too. That has to be hard on anything that is alive!
If you’ve got a hive dipping to -20F, it might be a good thing to try to warm it up a little bit the next day and give the poor bees a chance to reposition themselves for the next nights bone chilling cold. But I don't know.
The whole way we keep bees in the Northern parts of America makes little sense to me.
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Beeks make strange things.
The most amazing are Thanks giving day honey balls and Cristamas evening supper.
Open feeding is more than odd.
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One experienced beek (now the beekeeper of year) told that his hives remembered evil boys who threw stones onto hive last summer.
(- Even if bee generations have changed few times. )
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Finski, just wait for what I have in store for my hives come Valentines day :)
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I have always wondered why some BK wrap there hives in black tar paper??
I can understand the wind shielding aspect, but heating the hive on sunny winter days will cause the ball of bees to break prematurely and result in a higher consumption of winter stores.
Studies that I read show that a steady constant hive temperature makes things easier for the bees to maintain a warm bee ball in wintertime.
The bees need a quiet stable environment.
mvh edward :-P
"Different strokes for different folks."
Most BEEKs will try most anything they "think" might benefit their bees or themselves. We need only consider some of the crazy things BEEKs have done in the past (and present) to bees, intentionally or not, rational or not.
As I (hate) to say whenever asked "what's killing the bees?" 'We' are killing the bees (you can replace bees with your own favorite species).
"To be a friend of the Earth you must be an enemy of the people" TC Boyle
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Hello everyone!..All this brainstorming and washing is being invaluable to me! :shock: :-D I'm writing from the Kullu Valley in the indian Himalaya where at around 2000mt I'm in the company of a colony of Apis Cerana Cerana housed in a Warre circular hive,and thanks to most of your posts on hive insulation in the last couple of years I'm starting to appreciate the paramount importance of the thermoregulation of the hive to the thriving of the bees in the temperate climates of the world,and I look agape at the complexity,the mystery,the spiritual beauty, and the wisdom that the bee superorganism adaptations and behaviours entail and which, with your help, I, quite flabbergasted! :mrgreen: start now to comprehend.
I would like to comment on Bluebee fotos of the plastic sheet applied to the top of his hives for the observation of condensation;
There is a lot to talk about, but let's start about this:
Professor Jurgen Tautz in the amazing The Buzz About Bees pag.217 states that a strong colony of Apis Mellifera, presumably Ligustica and hived in a conventional Langstroth or Dadant, can produce 300kg of honey during a summer, although only a small proportion of it is present at any time in the hive. The 4/5 of it, 240kg, are literally "burned" to regulate the temperature of the brood both in winter and summer and to warm the winter cluster (2 million K joules for brood rearing and another 2million Kj for the winter cluster; the combustion of 1kg of honey produces 12000kj). This means that building a hive that is only 3 to 6% more energy efficient could save the 7.5kg of honey that according to the same author the bees consume to build the 1200gr of wax combs of a typical nest..making a hive 10% more efficient would not also increase the honey yield for the beekeeper, but would also profitably allow, if we are a bit intelligent, the bees to build their combs, the exoskeleton of the superoganism -fondamental organ of its immune system- and to be fed only honey.
BlueBee :), this method for observing the hive activities influences what you see,and your fotos are not indicating how different hives prevent or facilitate the formation of condensation! By opening the hive you force the condensation of the warm and humid air at the top of the hive,as the thin plastic sheet readily dissipate the heat to the cold air above. If the top is properly insulated the warm air underneath will retain its moisture and will be eventually transported outside thanks to the air circulation established by the temperature gradient between the warm cluster and the air outside; within an adequately insulated hive this "exhaled" air will shed some of its moisture only when it meet the cold drought of air entering from the hole.
What your picture are showing is that in a hive with a bottom entrance, the air above the cluster is warm and humid and the bees are scattered on the combs, maybe just relaxing, conserving energy (cfr."Outdoor Wintering of Bees" by E.F. Phillips, link by dereckm )while in a hive with a top entrance the air at the top,whose residence time is short by design, is cold and dry -that's why when it come in contact with the cold plastic sheet there is no condensation- and the bees ,as a result,cluster, insulating themselves and consuming thus abundant energy. Since the brood seem to require a relative humid -not wet!-environment, with a relative humidity,as far as I have gathered, between 40 and 70%- and since it seems thermodynamically efficient to create a "heat bubble" around the brood area and the cluster, your fotos illustrated to me the convenience of a bottom entrance.
In this amazing MSc thesis, "A CFD STUDY INVESTIGATING THE INFLUENCE OF BOTTOM BOARD GEOMETRY" by Cody Grant Thomson, the link of which was posted somewhere in the insulation threads, is explained how honeybees influence hive ventilation by adjusting the packing density of the winter cluster -incredibly important!- and how the addition of an empty space under the hive entrance creates a vortex of air that influences in a very positive way the rate of ventilation inside the hive,the removal of humidity and CO2 and all this especially when the temperature difference between the hive interior and the outside is small, i.e. in warm, humid days when it is most needed. To most Warrè beeks this extra space is known as Sump and it mimics the space found under the entrance of many of the natural bee nests investigated by Seeley and Morse (1976).
Thanks again to all of you for your invaluable help!
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piarelal;
Wow, what an excellent analysis. We'd Better be on our toes. You out there BlueBee?
Welcome to the BeeMaster Forum, hope we hear from you often.
I especially liked your description of the value in creating 'empty space' under hives, as its something I've done all along.
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Yes, I will have to keep on my toes. Some good thoughts from piarelal.
I’m sure bee keepers will debate the pros and cons of top vs bottom entrances and vents for eons. In an insulated full sized hive, I’ve been successful with top entrance hives and bottom entrance hives. From a thermal perspective, I completely agree that a bottom entrance (heat bubble) design is going to be more thermally efficient. The main reason I went with a top (actually a mid) entrance with my full sized hives is because of these:
(http://upload.wikimedia.org/wikipedia/commons/5/57/Striped_Skunk.jpg)
I don’t know if you have skunks in India or not, but they are a real menace to bees where I live. Where I live you need to keep the entrances at least a half meter off the ground or the skunks will claw up my polystyrene hives and kill the bees. So I either have to put my hives on stands or go with a mid entrance. I chose the mid entrance option since its cheaper (no stands) and easier on my back (lower to ground) to lift supers.
My full sized hives do have an empty space below them where I can monitor for mites. The bottom of the bee’s home is screened, and that sits on another box that is about 12cm tall. My nucs do not have such empty spaces though.
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Hei Man, your pictures are great! They perfectly visualize the flow of winter air at the top of the hive. Warm humid and CO2 laden air must rise on top of the bees, that's why when you open the hive there is no condensation in the central area; As this air move away from the centre it must become cooler and denser and therefore, in a well insulated hive, will tend to descend at the side without condensing, while opening the hive cool further this already relatively cool air under its dew point and forces its condensation.
Well :angel: :-D Now I'm tripping! The more I look into this and the more sci-Fi become the world of the bees..
From Wikipedia page on Natural convection:
"As the temperature difference between the top and bottom of the fluid becomes higher, significant differences in fluid parameters other than density may develop in the fluid due to temperature. An example of such a parameter is viscosity, which may begin to significantly vary horizontally across layers of fluid. This breaks the symmetry of the system, and generally changes the pattern of up- and down-moving fluid from stripes to hexagons,as seen at right. Such hexagons are one example of a convection cell."
A great article I found on the Warrèbeekeeping forum :
"Flow currents and ventilation in Langstroth beehives due to brood
thermoregulation efforts of honeybees" by Rangarajan Sudarsan, CodyThompson, Peter G.Kevan, Hermann J. Eberl. So long..
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Hei Man, your pictures are great! They perfectly visualize the flow of winter air at the top of the hive. Warm humid and CO2 laden air must rise on top of the bees, that's why when you open the hive there is no condensation in the central area; As this air move away from the centre it must become cooler and denser and therefore, in a well insulated hive, will tend to descend at the side without condensing, while opening the hive cool further this already relatively cool air under its dew point and forces its condensation.
Well :angel: :-D Now I'm tripping! The more I look into this and the more sci-Fi become the world of the bees..
From Wikipedia page on Natural convection:
"As the temperature difference between the top and bottom of the fluid becomes higher, significant differences in fluid parameters other than density may develop in the fluid due to temperature. An example of such a parameter is viscosity, which may begin to significantly vary horizontally across layers of fluid. This breaks the symmetry of the system, and generally changes the pattern of up- and down-moving fluid from stripes to hexagons,as seen at right. Such hexagons are one example of a convection cell."
A great article I found on the Warrèbeekeeping forum :
"Flow currents and ventilation in Langstroth beehives due to brood
thermoregulation efforts of honeybees" by Rangarajan Sudarsan, CodyThompson, Peter G.Kevan, Hermann J. Eberl. So long..
be careful with this last paper as it assumes that the shell of the hive is a perfect insulator (section 3.4 boundary conditions)
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Hello Dereckm, thanks for the tip!
What would be different in a real hive? The only obvious thing I can think of is that the real hive,when it's cold, would dissipate some heat to the surroundings and so the thermal gradient between the brood area and the rest of the hive, would diminish..slower flow..-without taking into consideration the effects of concentration of Co2 and water vapour!;or during a hot summer day the real hive would heat up speeding up things..
I am on the right path? What are the implications?
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You get additional internal convective flow due to the surface heat loss creating negative buoyancy.
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The surface heat loss must be inversely correlated to the R value of the insulated hive; do you know at what value of R this heat loss become appreciable enough to create negative buoyancy?
I presume that you agree that negative buoyancy in this case would depend on the fact that when the porosity of the brood area bee cover or the winter cluster decreases,i.e. the cluster contract as when the temperature drops, the dissipation of heat in this areas decreases too, which in turn decreases the flow of air from the cluster to the opening of the hive. In this conditions of slower flow, the air region right underneath the bees will start sinking because of its high concentrations of CO2 and water vapour. But when the bee cluster expands again, increasing its porosity, the heat released will rise and and with it the air flow...The hive breath!!! :shock: :-D
Dereckm have you read the study of Thomson Cody posted above? ..Thanks to Little John for this link... He was also a member of the team that modelled the Langstroth hive study.
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hey Dereckm, do you have any idea how a circular nest or hive might influence the flow? Thanks for the help!