# In hive temperature control with Open Mesh Bottom Boards



## AR Beekeeper (Sep 25, 2008)

There are those that believe the honey bee can't control the summer temperature in a hive with Open Mesh Bottom Boards as efficiently as they can when a solid bottom board is used. Can anyone describe for me the visual indications that the bees are struggling to control heat in the hive with an OMBB and failing? What should I see when I observe the outside, and what should I be able to see when I open the colony for an inspection?

What should be the condition of the brood in the brood nest if high temperatures have caused damage? How can a beekeeper judge the efficiency of one type of bottom board versus another? How are we to determine in the bee yard that the wrong type of equipment is being used? How many colonies should be used to get an accurate outcome? How do we get rid of bias? What other things should be considered in an attempt to determine if an OMBB causes damage to a colony?

What studies that actually involve OMBBs have been done concerning summer temperature control?

As a year around user of Open Mesh Bottom Boards I recommend them to new beekeepers, have I been missing something all of these years? Or is bottom board styles, and our opinions of them, a matter of personal preference only with no hard evidence to back our preferences?


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## Rusty Hills Farm (Mar 24, 2010)

If I remember correctly the Bee Informed surveys have had questions about SBBs and I thought the responses indicated a slightly higher survival rate with them than without, but I'm not sure I am remembering correctly. Maybe take a look at some of their recent survey results.

HTH

Rusty


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## Vance G (Jan 6, 2011)

YOu just want to fight. Success with them just proves bees can overcome all kinds of manmade foolishness. It has been raining for four days here with highs in the mid forties and lows around freezing. Sure makes me wish I was sporting them! Id get lots of style points along with the chilled dead brood.


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## Rader Sidetrack (Nov 30, 2011)

Here is the related thread that seems to have prompted the creation of this current thread: 
http://www.beesource.com/forums/showthread.php?324214-When-amp-where-for-screened-bottoms


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## Wandering Man (Jan 15, 2016)

Vance G, I think he is asking legitimate questions.

As a new beek it is difficult to know which side of an issue listen too, unless there is at least anecdotal information. It is even more difficult for a new beek when you consider that Great Fall's Montana, Walker Alabama, and Victoria, Texas all have different climates. We are harvesting vegetables out of the garden right now. My sister in Iowa hasn't even started planting. Our overnight temps are in the mid 70's, and I read someone on this forum in Wisconsin is still experiencing highs in the 50's.


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## whiskeylocker (Apr 28, 2016)

April 28 and its 25 degrees in Leb NH, Every night this week supposed to be in lower to mid 20's. Just got 4 inches of snow yesterday and they were plowing fields for corn. I am getting ready for my first year at beekeeping. I have read many writings about screened or solids. I am leaning towards solid bottom, but still not sure what to choose. With all of the info I have read via books, internet forums (such as this one), and trying to learn from others, seems the solid bottom is the way to go. Not very often do we hit triple digits where Im from in NH. I am still open to the subject though. I have built 2 hives and made 2 screened bottom boards because that's what I thought I wanted and at a local class that's what they recommended, of course they always throw in the Varroa Mite strategy in there. I would listen to Michael Bush and utilize small cell foundation and just go with a solid bottom. Seems the screened bottoms are more of a PITA. But I have NO EXPERIENCE in beekeeping. Like I said Im just starting too.


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## Chuck Jachens (Feb 22, 2016)

Temperature control is dependent on many factors in the hive, which leads us the discussion of environment climate control by the bees. I think screened bottom boards (sbb) are a good thing in my area. During the heat of the day, typically over 93 degree in the summer, the bees evaporate water which raises the humidity. The ssb allow air circulation which replaces the air with drier air. The bees are essentially running a swamp cooler in the hive to regulate the temp. Because of the heat and low humidity, a solid bottom board forces the hive to act as a water condenser to lower the humidity so the bees can then evaporate more water for the cooling effect.  This is less energy efficient than the swamp cooler method.

It makes more sense for me the use sbb in the summer. On the other hand, I close up the bottom for about 3 months in the winter because the hive sides act as a condenser and with limited air exchange, the hive is more efficient. 

Bee keeping is highly dependent on the local conditions and the physical characteristics of the hive. Your result may vary, but most of this discussion depends on a good understanding of heat exchange, thermodynamics, ventilation, and the hive materials plus the environmental factors of where the hive is located.

Luckily, the bees compensate for most of our mistakes.


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## dynemd (Aug 27, 2013)

There's also open screened bottom boards and closed screened bottom boards. I have a regular bottom board below my screen with a screened back door that I seal up in winter time with several layers of cloth. My thoughts on the amount of airflow that's optimal have changed over time to where I now feel they need less than I used to. In other words more ventilation is not necessarily better. It would be nice to have some double blind studies done in various climates instead of opinions...


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## AR Beekeeper (Sep 25, 2008)

No Vance, I am not wanting to fight. What I want is some one to show me evidence that a colony can't cool it's interior as well with an open mesh bottom board as with a solid bottom board.

I agree with you that the open bottom is not as efficient in a harsh winter climate as a solid bottom, that has been proved by the Iowa study on Russian Bees with OMBB. If my memory is correct, the bees on OMBB used 30% more winter stores than did those on solid bottoms. This is what I mean, that question has been proven, it is not someone stating an opinion as a fact, it is a proven fact.

I am still waiting for a post from anyone that can tell me what I should be seeing in my bee yard that would indicate heat stress in my colonies due to OMBBs.

I think we see opinions and personal likes or dislikes presented as facts, and we see advice given based on experience keeping bees in completely different conditions than those where the poster resides. Vance it would be foolish of me to try to give you advice on wintering bees in Montana when my experience is limited to Arkansas. The old saying "location is everything" works with advice also.


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## Vance G (Jan 6, 2011)

Wandering Man said:


> Vance G, I think he is asking legitimate questions.
> 
> As a new beek it is difficult to know which side of an issue listen too, unless there is at least anecdotal information. It is even more difficult for a new beek when you consider that Great Fall's Montana, Walker Alabama, and Victoria, Texas all have different climates. We are harvesting vegetables out of the garden right now. My sister in Iowa hasn't even started planting. Our overnight temps are in the mid 70's, and I read someone on this forum in Wisconsin is still experiencing highs in the 50's.


Bees need to heat a hive any time the ambient temperature drops below 93 f. When you turn on your AC IN your hot climate, do you open all the doors and windows to help cool the house? When I started attending this forum, SBBs were almost the law. The fad of the times. I recognize a number of names who shut up about them or converted them into oil pits for SHB. I just think of the thousands of packages right now desperately trying to cover brood and expand that will dwindle and fail. DARN SUPPLIERS! Sold me those sick bees propped up by chemical treatments and feeding! No wonder they died under my enlightened ministrations! 

Sorry for my passion but I am really fond of bees.


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## crofter (May 5, 2011)

I think this is not a simple yes / no problem to solve. Lots of variable inputs like ambient air temp outside hive, ratio of solar radiation to outside temperature input, how many frames of nectar are being dried, what is relative humidity of available outside circulating air, are there upper vents? If solar heat is a big effect could the air beneath the hive be enough cooler to influence the equation?

Bees can do a lot with their bodies to either fan air in or out of the hive and can physically impede circulation with their bodies by bearding out or clumping in openings or plugging screen openings. That said, their body heat production and their physical volume may become a negative influence to the hive cooling. Beyond a certain point they can panic, regurgitate honey and the system breaks down. One factor to consider is that evaporative cooling will cease to work when the internal air temperature and humidity reach saturation levels. A variable amount of air exchange will be required for optimum cooling effect. Too much intake of outside air is not a solution and too little will curb evaporative cooling.

From the perspective of retaining the cooled air and also evacuating the more humid air, I think upper ventilation would be more effective but other items may outweigh that factor in the overall equation. 

I doubt that intuitive thinking alone is up to solving this one definitively.

For my cold winters and very moderate summer temperatures screened bottom boards are clearly not on my menu, now where daytime temperature get up well over 100 degs and high humidity I would have to do some pondering! 

Not going to go there though!:no:


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## Chuck Jachens (Feb 22, 2016)

"When you turn on your AC IN your hot climate, do you open all the doors and windows to help cool the house?". 

Actually the ac unit that uses refrigerant works as a closed system in your home. The heat inside your home is disipated outside. Bees can't do that, they use evaporative cooling like a swamp cooler. A swamp cooler requires an exchange of air with the outside other wise the humidity needs to condensate inside the house. The hive walls can do this only if there is enough temperature differential through the wall. Otherwise ventilation is needed in the hive.


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## crofter (May 5, 2011)

Chuck;

I agree that ventilation is required; do you agree that beyond a certain point the net cooling effect diminishes and that the placement of intake and exhaust ventilation will affect the outcome?

If this were a static exercise with a known amount of water dripping on a given area of evaporative surface and ventilation points fixed in size and location, the answers would be much more predictable. The fact that the bees actions are a self willed and dynamic variable takes it far from having a simple solution.


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## psfred (Jul 16, 2011)

Several things to consider here. One is that there are two designs of screened bottom board that I have seen, and I won't use one of them (and neither do the bees, they propolise them shut) -- that is the one with a screen over an open space with a board an inch or so away with no ends on the bottom frame. 

The Kelley design has a sticky board that fits into the bottom of the hive stand an inch or so below the screen that pretty much seals the hive up. I use those, and only pull the sticky board back an inch or so if I see a lot of bearding on the hive. Otherwise, closed up.

Bees know how to ventilate a hive through a small opening, and they fan air over droplets of water to cool it in the summer. Having the whole bottom of the hive wide open prevents them from supplying cooled air and I presume screws up their control of where that cooled air goes. No data on chilled brood, hive activity, etc. but I don't lose hives in the winter with the sticky in and only pulled back slightly in the summer.

Bees are pretty tough -- a local beek found a swarm from last year that overwintered out in the open hanging on a big branch, and while we had a mild winter, that doesn't mean no snow or temps in the teens a couple nights! However, I see a big difference between bees surviving and bees making honey for me, so I tend to do what I can to help them stay healthy and brood up in time for the spring flow.

Peter

Peter


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## Nugget Shooter (Mar 28, 2016)

Interesting and informative reading her and thank you all for the input. I have the type that will open or close about an inch below the screen and today we hit 101 degrees in the shade and dry as popcorn with humidity at 6%. I have the bottom open a bit to help vent a new package hive from April 18th and they are doing great. I see much debate about the bottom screen and we use a swamp cooler on our house all summer, as long as humidity is below 40% it works great, but during our Monsoon Season when humidity and dew point are high it's efficiency suffers so we add fans to move more air and it works. New to all this, but that was my thinking when using a SBB and being able to help the airflow when needed seemed a good idea. So I will continue to read and learn now.....


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## challenger (May 27, 2009)

Well 17 replies and STILL no "proof" about SBB has been offered. I think this is because there IS no proof. SBB are like most other things that are sold as something the, "bees need" so ignorant people like me, AND those that wrote/write articles stating that SBB are best, sign on to this. Why? Because we humanize our beekeeping. At least to the extent that we feel it makes perfect sense to do stuff for bees that might translate to better life for bees. The list of things that per let have come up with, that make life easier for bees, is far longer than the list that bees really need. This is just my opinion. 
Think about how much smaller the catalogs from the bee suppliers would be.


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## crofter (May 5, 2011)

We chop down all the truffula trees to make our thneeds! From the Lorax.

_I’m being quite useful. This thing is a Thneed.
A Thneed’s a Fine-Something-That-All-People-Need!_


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## Planner (Apr 3, 2016)

You are correct. The better quality SBB have an insert that may be used or pulled to allow for complete circulation. I have used them for years. In the colder weather the insert is slid in from tieback of the hives SBB and generally converts the SBB into basically a standard bottom board and the external air circulation is almost closed. In the warmer months I remove the insert and allow for complete circulation. In this respect I don't see much of an argument for using a SBB or not using one, as the bottom board can be simply converted to accommodate any weather condition. For example,I will leave my inserts in until the weather is about 70 degrees and then remove for the summer. I have recently ordered one of these products from Brushy Mountain and found them to be f very poor quality construction wise and their inserts are cardboard and poor qaulity.


psfred said:


> Several things to consider here. One is that there are two designs of screened bottom board that I have seen, and I won't use one of them (and neither do the bees, they propolise them shut) -- that is the one with a screen over an open space with a board an inch or so away with no ends on the bottom frame.
> 
> The Kelley design has a sticky board that fits into the bottom of the hive stand an inch or so below the screen that pretty much seals the hive up. I use those, and only pull the sticky board back an inch or so if I see a lot of bearding on the hive. Otherwise, closed up.
> 
> ...


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## challenger (May 27, 2009)

Perhaps a study where swarm traps are put out made with, and without, screened bottom boards? 
Personally I've never removed a hive in a location that was screen at the bottom. Every home, condo, tree, etcetera etcetera, has had a closed bottom lol. 
I've caught many swarms in traps where I've used Soil cloth fabric for the bottom. Mainly because I had it and it was easy to staple to the traps. It let's air flow I guess but probably not 5% of the way #8 screen would.


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## Michael Bush (Aug 2, 2002)

There have always been a higher number of swarms/packages abscond from open screened bottoms than solid bottoms.


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## BeeAttitudes (Dec 6, 2014)

Michael Bush said:


> There have always been a higher number of swarms/packages abscond from open screened bottoms than solid bottoms.


Wouldn't this likely be dependent on where your hives are located? In other words, would this be true in Florida, Texas or Arizona? Maybe not.


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## BeeAttitudes (Dec 6, 2014)

Vance G said:


> Bees need to heat a hive any time the ambient temperature drops below 93 f. When you turn on your AC IN your hot climate, do you open all the doors and windows to help cool the house? When I started attending this forum, SBBs were almost the law. The fad of the times. I recognize a number of names who shut up about them or converted them into oil pits for SHB. I just think of the thousands of packages right now desperately trying to cover brood and expand that will dwindle and fail. DARN SUPPLIERS! Sold me those sick bees propped up by chemical treatments and feeding! No wonder they died under my enlightened ministrations!
> 
> Sorry for my passion but I am really fond of bees.


Hmmm......bees don't have an air conditioner so it seems you should be comparing them to homes/houses without AC. And in houses without an AC, then yeah, you do open the doors and windows to cool down the house.


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## Rader Sidetrack (Nov 30, 2011)

Before houses had mechanical air conditioning, houses often had evaporative coolers (commonly known as 'swamp coolers'). Swamp coolers are a human version of bees' evaporative cooling in a hive. 

Both of them spread a thin layer of water out over a wide area to allow the water to evaporate and cool the resulting air to _BELOW_ the ambient temperature. And while a _controlled_ air exchange is needed to make evaporative cooling work properly, opening all the doors and windows in a house that one is trying to cool with a swamp cooler would cancel out any cooling effect. 

If the temperature outside is 100 degrees, no matter how many doors or windows you open, the temperature inside the house will _never_ get below 100 degrees. With properly managed ventilation, a house with a swamp cooler can indeed lower the inside temperature _below_ 100 degrees.



> The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation), which can cool air using much less energy than refrigeration.
> 
> _More on evaporative cooling here:
> _https://en.wikipedia.org/wiki/Evaporative_cooler


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## AR Beekeeper (Sep 25, 2008)

In the absence of any suggestions of things to look for in a hive of bees that are in hot conditions that may indicate the need to ventilate, or the efficiency of the hives ventilation control, I will make a suggestion. 

Those of you that have screened bottom boards that have a closure board that completely covers the bottom can do this test in your own bee yard and make your own assumptions as to what is happening. You may want to take a hand mirror with you so that you can see the underneath of the bottom board and see what any bees there are doing, such as just hanging out, or passing nectar in or out of the hive, or fanning to cool the hive interior. 

Pick a hive that has a strong population of adults, and on a sunny day that is warm (80 +), but not warm enough for the hive bees to be fanning at the entrance or bearding, look closely at the entrance and see what the bees are doing. Foragers will be coming and going and guards will be checking incoming bees but look specifically for bees that are fanning. After you check, insert the closure board. Note the time and watch the entrance.

What happens with the bees at the entrance? Do the numbers increase and do any of the bees become ventilators, fanning to start the air moving over the box face and at the entrance? If the bees, with an open bottom board had no need to fan, but do when the insert is in place, what is happening inside the hive?

Give it a try and see for yourselves, perhaps your colonies and your location differ from mine (82 at noon, real feel 90, wind SW at 6), let me know how your colonies react.


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## BeeAttitudes (Dec 6, 2014)

Rader Sidetrack said:


> Before houses had mechanical air conditioning, houses often had evaporative coolers (commonly known as 'swamp coolers'). Swamp coolers are a human version of bees' evaporative cooling in a hive.
> 
> Both of them spread a thin layer of water out over a wide area to allow the water to evaporate and cool the resulting air to _BELOW_ the ambient temperature. And while a _controlled_ air exchange is needed to make evaporative cooling work properly, opening all the doors and windows in a house that one is trying to cool with a swamp cooler would cancel out any cooling effect.
> 
> If the temperature outside is 100 degrees, no matter how many doors or windows you open, the temperature inside the house will _never_ get below 100 degrees. With properly managed ventilation, a house with a swamp cooler can indeed lower the inside temperature _below_ 100 degrees.


If the water is spread out over a "large area" to evaporate, then I would assume it is spread throughout the frames (or at least that would be the most efficient). Assuming the hive has a top entrance (or other venting) to allow air flow, then an open screen bottom would allow air to move more equally over the entire surface area of all the frames. If the bottom is closed, then air only enters thru the bottom entrance so it seems it would mostly allow evaporation in the front portion of the hive near the entrance area (whatever size that is). So I would guess that a screened bottom board allows for more cooling which is nice in warmer climates.


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## Rader Sidetrack (Nov 30, 2011)

You seem to have overlooked the "not having the windows and doors all open" part of the evaporative cooling process. With an _open_ screened bottom, how are the bees going to 'control' the ventilation to match the water they are bringing in?


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## AR Beekeeper (Sep 25, 2008)

The way they always control the ventilation in the brood nest, by opening and closing the seams between comb with their bodies.


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## Nugget Shooter (Mar 28, 2016)

On swamp coolers, been using them here in Arizona for most my life, that said.... You must have as much air going out as in! In other words enough windows or vents open to allow the equal amount of moist air coming in to push warm dryer air out....

Carry on.


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## Michael Bush (Aug 2, 2002)

There are some significant differences in a "swamp cooler". First the evaporation is taking place before the air gets into the house in order to cool the air. The bees are bringing in dry air and evaporating the water in the hive to cool the hive. The air going out, in both cases, is not dry air. It's wet air. In a house being cooled with a swarm cooler you have to move as much air out as in, of course, but you took hot dry air, ran it through the cooler and turned it into cool wet air and pumped it into the house which forced warmer wet air out.


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## missybee (Sep 6, 2014)

Here is Maryland, wet, humid, hot in the summer, we can hit 90 plus with heat index of 120. Our hives are full sun. We run SBB all the time, with screened inner covers in the summer. The hives, in our eyes, are thriving. Solid brood patterns, they have been filling the honey supers for the last three-four weeks. 

We do put in a solid inner cover in the winter full of sugar fondant. With our warm falls we are finding we need to feed the bees multiple times over the winter, even with leaving them a lot of honey.

I do close 1/2 of the screened bottom board down in the winter, put extra insulation under the hive lids, wind breaks around the hives, the hives stay nice and dry the bees do fine. 

My observations of our hives.


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## ChuckReburn (Dec 17, 2013)

Michael Bush said:


> There have always been a higher number of swarms/packages abscond from open screened bottoms than solid bottoms.





BeeAttitudes said:


> Wouldn't this likely be dependent on where your hives are located? In other words, would this be true in Florida, Texas or Arizona? Maybe not.


We definitely see a higher rate of absconds over screened bottoms in Texas. Two years ago when screened bottoms on Top Bar hives were the rage, one of the package producers had so many complaints over absconds that they were offering package queens only with a clipped wing.


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