# Dave Cushman's Ventilation Theory



## beeware10 (Jul 25, 2010)

with one bottom entrance the bees bring air in one side and out the other side. can be seen with light smoke. again the bees know what they are doing. with all the fanning going on there is no natural convection.


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## Solomon Parker (Dec 21, 2002)

Perhaps you should read the premise again. Why is there fanning and smoking going on in the winter?


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## Riskybizz (Mar 12, 2010)

I think that Dave Cushman (who passed away on February 21, 2011) was a very well known, knowledgeable and respected beekeeper worldwide. If it is your intent to question his ventilation theory via this post, would you mind also posting your qualifications and research, that led you to your assumptions so that we can better explore the two. Maybe we can then discuss these theories in greater detail.


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## Riskybizz (Mar 12, 2010)

Sol 

Apologies. I did read the post? Perhaps its just the way its written? I wasn't able to dedect a clearly defined premise. Sol: "This one appears to me to provide better ventilation without creating a chimney effect. What do you think" ? I don't think it does. Maybe you could enlighten us as to why YOU think it provides better ventilation.


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## Solomon Parker (Dec 21, 2002)

Dave made lots of experiments in a more or less scientific way. He wrote down this theory, of which I posted a link, but he did not include the option I am exploring in his 'research.' I am seeking opinions or experience, preferably experience.

It's an open ended question.


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## Adrian Quiney WI (Sep 14, 2007)

Another factor to consider is that Dave was English. In Britain it is rare for the temperature to drop below 32F for more than a week at a time. Bees are kept in such varied climates that without every region performing the same experiment we are never likely to find whose theory of ventilation is correct. 
BTW last year at my bee club an old science teacher beekeeper showed us a photo of a hive he opened in the winter with a clear plastic inner cover. The bees were clustered centrally in the top box. The photo showed there was no condensation directly above the cluster and the condensation started at the edge of the cluster and was most obvious on the very edge of the box. He then showed us the chemical formula for honey and its metabolized products which were a lot of CO2 and H20. He didn't wrap his hives believing that the water would breathe out through the wood - which made no sense to me as the wood was painted, and in Minnesota would be frozen in the winter. 
I guess my point is that bees are such adaptable critters that we need some real science, real world experiments to determine what happens in the hive for ventilation and what is best for each area.


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## WWW (Feb 6, 2011)

I brought a hive through the winter with no upper ventilation and a 1"x1" opening at the bottom, used an added heat source with a plexi-glas inner cover to weekly view their condition without exposing the hive to frigid temperatures. Zero condensation and a healthy spring hive was the result, this was my first of hopefully many experiments to find the best setup for wintering beehives. Upon just reading Cushman's theory I am very much in agreement with him. I feel as beekeepers we need to always try to look beyond what has been accepted as the normal way of doing things,,,, we owe it to the bees.


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## Roland (Dec 14, 2008)

Sol - I am completely confused. Did he not talk of sealed and insulated roofs?
I agree completely with what he wrote. We do not use upper entrances in winter, and have not for at least 50 years. 

Crazy Roland


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## WWW (Feb 6, 2011)

Roland: Thats the way I read it, insulated roof.


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## Solomon Parker (Dec 21, 2002)

Yes he did. Don't focus on what he said about configuration, instead think about thermodynamics. I'm exploring Michael Bush's top entrance only idea. I do realize the chimney effect is probably sub-optimal, but I have a skunk problem and can't do a lower entrance.


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## DeeAnna (Nov 5, 2010)

Adrian wrote "...I guess my point is ... we need some real science, real world experiments to determine what happens in the hive for ventilation..."

I would agree. Convective air flow does not necessarily behave as "common sense" would suggest. I cannot speak about convection in beehives, but I do know that engineering studies of natural convection in hog confinement houses and home attics sometimes show air flow patterns that are quite different and more subtle than what one would expect. --DeeAnna


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## WWW (Feb 6, 2011)

Solomon: Love the name by the way, your top entrance theory concerns me in that I would think the hive would need to be monitored closely and the opening size adjusted carefully to get the correct balance between heat loss and ventilation, and would this remain a constant as the outside temperatures fluctuated. With the opening on the bottom I would think the temperature change inside the hive would be more gradual, since the heat is actually held inside and the loss would be through the wood box. Cushman stated that naturally bees will have an opening just a little below the half way point, have you done any experaments with this, it might be the halfway point between two extremes. Might be something to look into next winter. I do think insulation is a big factor as condensation also forms where heat contacts cold, add to that moist air and you have the worst of conditions. I have also considered the common inner cover saging in the middle from moisture and funneling it directly into the cluster which is usually in the center to escape the cold comming in from the sides of the hive box. I always enjoy your lively posts....... Bill


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## Roland (Dec 14, 2008)

Now I am even MORE confused. Cushman was speaking of wintering configuration. There are no bee out in winter, so no skunks? In summer, when there are bees and skunks out, we use upper entrances . I must be missing something.

Crazy Roland


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## Solomon Parker (Dec 21, 2002)

Roland,

There are skunks in late winter here. They just about cleaned my clock this year. That's why I'm switching to upper entrances similar in theory to how Michael Bush does his. http://bushfarms.com/beestopentrance.htm


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## minz (Jan 15, 2011)

I caulked my reversible bottom boards and painted them (after going to Screened bottom boards). If I get any swarms this year I am going to use the bottom boards for a migratory cover with top entrance in the same manner as MB’s article in those hives. I was also made some spacers shown on the Queen Excluder article (more of a middle entrance) to be used between the hive and supers. Since I have new telescoping covers I do not want to go all top entrance before at least getting them dirty! :doh:One thing to say about this hobby is that there is never an end to options and opinions.


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## Roland (Dec 14, 2008)

Sol - my bad, our skunks don't come out till it warms up, then the bees can take care of themselves. 

Some one posted a anti-skunk trick you migth try. I believe it was a landing board sized piece of wood(1 x 10 x 20), with 1 1/2 nails pounded thru it every inch or so. It was left where the landing board goes with the nails pointed up. 

Are you that bad of a shot(he he he)?

Crazy Roland


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## Solomon Parker (Dec 21, 2002)

I have been using nice rusty carpet tack strips and they were working for a while, but the critter must have gotten extra hungry.

Oh, and I had the loaded gun in my hand, but I could never catch the varmit in the act. I guess I just like to sleep to much. I don't know if you have "skunk season" like we do, it's the time of the year when there are nearly as many dead skunks on the road as dead cars. (This is Arkansas you know, and no, I'm not from here.)


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## HONEYDEW (Mar 9, 2007)

The steel plates used to hold roof trusses together also make nice guards..


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## WWW (Feb 6, 2011)

If skunks is your problem and not the opening in the hive, then run a electric fence around your hives to protect them and let the skunks feed on yellow jackets. You will be protecting your hives from the both of them.


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## S&H (Feb 25, 2010)

An electric fence will protect hives from yellow-jackets also?
Perhaps I misunderstood...


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## WWW (Feb 6, 2011)

electric to protect hives from skunks, skunks eat yellow jackets.


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## Solomon Parker (Dec 21, 2002)

Only if they nest in-ground or near, which not all of them do.


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## odfrank (May 13, 2002)

An electric fence will have your property smelling like skunk spray a lot. I raised the lower wire on my vegetable garden fence because of this problem.


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## odfrank (May 13, 2002)

So what should we conclude from Dave Cushman's Ventilation Theory? Should I have SBB or not? Should I have upper entrances or not? What kind of lid should I have? How do I incorporate insulation into a migratory cover?


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## sqkcrk (Dec 10, 2005)

I don't mean to seem to question the ideas and exploration into hive ventilation, but isn't it possible that this is being over thunk?

WFS, is there an Engineering term for overthinking something?

I know Dr. Tom Seeley has investigated swarming and what bees do in determining what size a cavity to take residence in, but has any study been done on hollow tree trunk hives and how they work? Most of the ones I have observed have only one hole, which can be just about anywhere in relation to the combs of the colony. But are some entrance locations preferable?


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## Solomon Parker (Dec 21, 2002)

sqkcrk said:


> I don't mean to seem to question the ideas and exploration into hive ventilation, but isn't it possible that this is being over thunk?
> WFS, is there an Engineering term for overthinking something?


You know what Mark, you're right. If it's good enough for Michael Bush, it's good enough for me. Plus I don't really have a non-electrified, non-violent choice. The bees will have to deal with it.

Assaninalitical?

I thought of an experiment that could help us determine exactly where the bees would like their entrance. I could take a pile of boxes, and drill a line of half inch holes from top to bottom at one inch on center. The theory follows that the entrances the bees don't want, they would plug up, leaving the desired entrance at the desired height. Would you like to donate some boxes that I could try this on? I will dutifully report the results back here in a year.


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## sqkcrk (Dec 10, 2005)

That is the most joyful response I have gotten in a long time. Did you just think that up off the top of your head? Or is it really something you use in your office? you gave me a good laugh.

Entrances prefered by bees. I was working some of my cvolonies yesterday and one hive had bees coming out of the long side, instead of out of the entrance at the bottom front. Understand that almost none of my hives aree so tight that the bees have to use the front entrance at the bottom. Most of my colonies have multiple choices, and use them.

In this case, the one on the side was the one getting the most use. Which is something I had to pay attention to, since I stand at the side to work my hives.

I believe that most tree hives have comb facing the entrance, rather than in line w/ the entrance, as most of us have in our hives today. I'm almost certain that this is true in skep hives.

Does that say anything about how the bees would like the combs in a hive oriented and thereby effecting ventilation? I don't know.


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## Solomon Parker (Dec 21, 2002)

I came up with that word, but it was based on another word. I'm pretty sure no one has ever used it before.


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## AR Beekeeper (Sep 25, 2008)

Elbert Jaycox in his book Beekeeping Tips And Topics told of a Russian study on hive entrances that was done in 1977. It stated the bees prefered an entrance 2.5 inches above the bottomboard.


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## sticbow (May 29, 2011)

Interesting topic!! Has anyone come up with any conclusions since it was last discussed in March?


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## Solomon Parker (Dec 21, 2002)

Well, I am using both lower and upper entrances this year on most hives, and just upper ones for a couple. The hives are noticeably dry inside. Not all that much to report.


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## max2 (Dec 24, 2009)

"I could take a pile of boxes, and drill a line of half inch holes from top to bottom at one inch on center. "

I think this experiment has been done.
I have been asked to shift hives which had entrances all over the place ( not deliberate - mind you - the result of negelect) and all where in use about equally ( judging from the dark stain)


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## Solomon Parker (Dec 21, 2002)

My typical hive configuration is a 1 1/2" hole in the front of the bottom box and then a 3/4" slot across the top in front. The bees started on the bottom entrance with the original nucs and splits tend to want to keep using those. The longer established ones are accustomed to using the upper entrance. I have skunks in the early spring, so I have to close the bottoms, hence last years hive like the uppers.

This year, some hives had become accustomed to using the broken corners of boxes as the primary entrance until I switched them out.

My question was originally less about where the bees prefer to go in and out and more about the optimal ventilation. Everyone uses their own. Roland likes bottom entrances, Michael Bush likes upper entrances, Michael Palmer likes both. I say try everything and do what works.


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## max2 (Dec 24, 2009)

I just looked at " Parker Farm's" website and this pop-up appeared :http://www.brisbaneskylights.com.au/content/show/65321?gclid=CNza8Nvz9awCFVCApAodxw0CRg

Maybe this is the next step?


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## Solomon Parker (Dec 21, 2002)

What an insult! Surely you did not encounter a popup on MY site!?!  I disavow any knowledge of any popups.

I have wanted to get those for my attic for a long time, I have the perfect climate for it. But those things pull 1200 cfm or better. That means one of them could change out the air in a double deep hive over 400 times a minute. A bit overkill I think.

I like hives where the bees are able to handle business on their own, but it's a good thought.


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## max2 (Dec 24, 2009)

What an insult! Surely you did not encounter a popup on MY site!?! I disavow any knowledge of any popups.

!!!!I'm looking at your site in Australia. I get Australian advertising also on Beesource. They should at least pay you. I have no idea how these things work.

I have wanted to get those for my attic for a long time, I have the perfect climate for it. But those things pull 1200 cfm or better. That means one of them could change out the air in a double deep hive over 400 times a minute. A bit overkill I think.

!!!!Yes, poor bees would have no time for anything else but fight against the wind!

I like hives where the bees are able to handle business on their own, but it's a good thought. 

!!!!!Yes, ventilation is generally not an issue here. We get few extremes.


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## Solomon Parker (Dec 21, 2002)

I have ads, but no popups. Those dirty pirates!


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## bluegrass (Aug 30, 2006)

Speaking of Cushman and his recent death. His site has a lot of valuable information on it that will be lost once his web hosting lapses. Anybody making an effort to save all this data before we loose it? I have saved some stuff to my hard drive, but an effort should be made to save everything.


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## Solomon Parker (Dec 21, 2002)

That's a good point.


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## max2 (Dec 24, 2009)

This is what it says on the website:

David A. Cushman logo, linked to Biographical Details


Notice

Dave Cushman died on 22nd February 2011. Shortly before he died he asked me to take over his websites. I later learnt he bequeathed them to me. I am a beekeeper and we discussed the future of the beekeeping website, with Dave telling me I could develop it how I wished. 

He specifically asked that all non-beekeeping websites and pages stay exactly as they are and I promised I would maintain them as long as I could. I understand his reasons and will respect them. They will be archived, but still accessible.

I will try to maintain and develop the beekeeping website in a way that Dave would have approved and to maintain his high standards.

The beekeeping world is grateful to Dave Cushman for the effort he put in on providing what many consider to be one of the world's finest beekeeping websites and I will do my best to maintain it as such. I want it to continue to be known as "Dave Cushman's website" so Dave is permanently remembered for his huge contribution to beekeeping.

Roger Patterson

It looks like that the site will continue. I did notice that some parts had not been up-dated for some time. It is all a big job.


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## sticbow (May 29, 2011)

So if your using a bottom entrance here in Wisconsin, as Roland is, how would you keep the entrance free of snow?


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## gjd (Jan 26, 2011)

sqkcrk said:


> I believe that most tree hives have comb facing the entrance, rather than in line w/ the entrance, as most of us have in our hives today. I'm almost certain that this is true in skep hives.


I was rereading this thread after it got bumped yesterday, and this caught my eye-- I've occasionally wondered the same thing about comb orientation, and had an idea-- look at this video, at 3:34. It shows a skep beekeeper with an upturned skep, and you can briefly see the top opening and comb oriented towards the opening. If the link doesn't work, it's "Heathland Beekeeping -1" on YouTube.
http://www.youtube.com/watch?v=upbONroWPic&playnext=1&list=PL74CCC61E24A25F8A

And, of course, this means that top-opening skep hives with German bees in Lower Saxony like to build comb pointed towards the entrance. In this hive. I haven't rewatched the entire series to see if it's consistent.
Greg


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## Barry (Dec 28, 1999)

sticbow said:


> how would you keep the entrance free of snow?


Shovel. That's the fun of wintering bees around here. It gives us a reason to go out and check on the hives every couple of weeks.


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## Roland (Dec 14, 2008)

If there is snow in front of the hive, the should stay in the hive. Don't worry about it. When it is warm enough to fly, the snow will melt.

Crazy ROland


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## Michael Palmer (Dec 29, 2006)

I don't shovel snow away from bottom entrances...35 apiaries. I add an upper entrance when I wrap in the Fall.


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## Daniel Y (Sep 12, 2011)

Solomon Parker said:


> Read this page: http://www.dave-cushman.net/bee/ventilation.html
> 
> Now I can see his chimney effect with a hive with both top and bottom entrances. That's pretty obvious.
> 
> ...


Not so. heat rising and leaving through a top entrance will create a draw (Chimney effect) Regardless of where the source of fresh air is located. In the case of a single top entrance the hole will serve both purposes. a portion of the hole letting air out while the remainder draws air in.

In the bottom or SBB examples written about it looks like heat is being conserved by keeping all entrances at the bottom. Warm air rises, and the interior of the hive is almost always warmer than the outside air in winter. Imagine the hive acting as a hot air balloon holding in the warmer air. With the opening at the bottom the air is able to keep the heat but pass some of the moisture if not a lot to the cooler outside air. In fact humidity will be lost at even a small opening by a startling degree. It is not necessary that the air pass by the opening in fact. the dryer outside air will act like a sponge on the entire air mass. I know this for a fact due to having designed and built several chambers to control both temperature and humidity. even a small hole in a chamber will allow all humidity to be lost. The thinking that air has to leave the hive in order for moisture to is incorrect. The only additional thing being lost in a top entrance is heat and stale air.

With all respect for the author of the linked writings his knowledge of thermal transfer, humidity transfer and thermal movement are severely lacking. His description of how warm air will move is not even close to accurate. heat does not move in clouds like a mushroom. it moves in waves. in addition it is strongly subject to many outside influences. As just one example. your hive has one side that faces toward the sun and one that does not. the shaded side will be much cooler as a result. This cooler wall could very well have enough impact on the heat inside the hive that all heat is drawn to this wall within the hive. It will not travel there as a cloud or mist that covers every portion of the space. it will travel as a stream or river not effecting any other space but the narrow stream. It may not travel through the air at all but through every object in the hive.

You cannot address the cold surface of the top of the hive and disregard the cold surface of the shaded side of the hive. the heat is not concerned with where the cold spot is. it will be lost to that cold spot regardless of where it is. Condensation on a wall may be less of a concern on a wall than on the ceiling. But in regard to conserving heat nearly all will be lost in the end.

In general I also do not agree with the concept that the bees generate the heat for the hive. I base this belief on what I know about myself and my ability to heat my environment. It woudl not be possible for my body to heat even a small enclosure against winter cold. in order for me to conserve heat well enough to protect from that environment, my encloser must be much closer to my skin. in fact nearly touching my skin. reducing any additional air space to nearly non existent. in fact if any air does penetrate this space it is felt as a chill immediately. It requires a sweater, coat, sleeping bag or blanket. My body is not able to warm the surrounding air at all. I believe that the hive receives heat from Solar Gain with the mass of the hive and it's contents acting as a thermal battery.

Regardless of the exact hows and whys. I do believe overall the theories are correct. I do not think conservation of heat is as much of an issue as the elimination of humidity and the prevention of condensation on surfaces it is not desired. a very then material over the top of a hive would in general be quite different than what bees woudl tend to find themselves in naturally.
Take the tree the author uses as the example. the ceiling in a rotted out tree is anything but one of the thinnest surfaces of the container. A cool moisture condensing surface would not be above the bees in this case. It would in fact be fare more likely the walls that are the coolest surfaces and even then it is questionable that they are ever cool enough to condense moisture in the hive at all. A rotting tree is generating heat of it's own.


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## crofter (May 5, 2011)

Lots of conjecture and not much science! That is all fun but I do not like to see it reflect on the capabilities of Mr Cushman. I suspect that his description of events was a dumbed down version to get the general ideas across. I could pick a few technical holes in some of the previous explanations as well. Experiments have been done in freezer boxes that pretty well isolates the influence of solar thermal gain. It probably has already been done but if a person wanted to replicate the math he could look up the calorific value of the available honey, convert to BTU.s and know how much heat the bees had in the bank to spend for the winter. There is a direct relationship between the honey weight metabolized and the water produced but the big unknown is the local conditions.. Winter here has such low humidity that static electricity is a snapper. Wood dries quicker than summer time. It does get -40Fah. though. Hardly describes conditions in jolly old England or many other keepers environments.

A bit like the parable of the seven blind men and the elephant! None could see but they all had a different vision of what the animal looked like.


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## rwurster (Oct 30, 2010)

Got a chance to check my bees today and all my hives were out flying, there were tons of bees on the watering bucket and it looked like they 'drank' about a gallon in 5 hours. There was 6" of snow so the bottom 2" of each hive was covered but I have top entrances only so they were able to get out and about. I use a 3" entrance thats notched into a sbb which has a quilt box on top of it. Then theres a tassle from some hay grazer stuck into the entrance. The bees chewed out a few to make their entrance bigger and propolized a few to reduce it. Seems to be working, no dead outs, they were doing housekeeping (removing dead bees) the snow is covered in yellow bee poop, i even got head butted by a few fiesty ones. We've also already had 3 day stretches of -17 at night and low teens during the day. Highs mostly around high 30s to low 40s. My mentor has already had 12 dead outs, out of the 200 colonies that didnt go to California. He uses 'mid' entrances... a 3/4" hole drilled into the middle of the sides of his supers with a bottom entrance. Top entrances are working great for me thus far.


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## Vance G (Jan 6, 2011)

I too checked bees today. Amazing how the clusters were against the sunny side! I have a commercial wrap on but it is light on insulation. everyone alive though I think I will put dry sugar to the half who are up under the cover already even though they have lots of stores left. I wish I would get a couple feet of snow cover to insulate mine! Some canadian beeks cover theres with front end loaders when it snows! Use loose snow of course. Do not be afraid of your colonies going under! It is the best of all worlds!


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## Mtn. Bee (Nov 10, 2009)

Had a old retired beek (now in his 80's) tell me one winter he had a colony that tipped or leaned over but did not go all the way over and the bottom entrance filled with snow.
He did not notice it (probably was a heavy snow year) and the bees died because they could not get air!


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