# TBH Screened Bottom Board



## Nectarcollector (Jan 31, 2010)

Here is some information for you to look at.

http://www.countryrubes.com/


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## buckbee (Dec 2, 2004)

angryhippie said:


> This will be my first year beekeeping and I have lots of questions. I have decided to try out both a Langstroth Hive and a Top Bar Hive. I have built my hive based on plans for the Original Backyard Hive, except more with the dimensions of the Golden Mean hive, but I am trying to decide whether I should use a solid bottom board or a screened bottom board. Please let me know your opinions.


I am not familiar with the climate in your area, but mine is relatively mild and damp, although the last two winters have been quite harsh.

I find that solid floors cause a build-up of moisture, and I have much better results with mesh floors, or no floor at all.

Top insulation, bottom ventilation is my rule now.


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## Ben Brewcat (Oct 27, 2004)

A screened bottom with a slide-in tray is the best of both worlds: you can ventilate or close it, and also monitor for mites. Despite what some TBH proponents say, you still need to monitor. TBHs do not radiate magic mite-killing rays. 

Ventilation seems to be one of the main things that can be improved with TBHs.


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## bigevilgrape (Aug 21, 2008)

Ben Brewcat said:


> TBHs do not radiate magic mite-killing rays.



But the guy who sold me my hive said....:doh:


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## Zonker (Mar 10, 2010)

Everything I've read (and some of it was actually university research stuff) says that the screened bottom is great for a bunch of reasons even in the winter.

I made my bottom as a hinged door so that it could be easily opened and brushed off. I'll send you my plans if you're interested. Just email me at [email protected].


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## Michael Bush (Aug 2, 2002)

I wouldn't bother with the screened bottom board. I don't see any difference in Varroa from it.


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## MIKI (Aug 15, 2003)

Screened Bottoms were NEVER intended to be a ventilation defice they were developed at the bee lab in Beltsville Maryland as a mite monitoring device and in that respect are invaluable!

there is also plenty of references in scientific journals that if left open the resulting lowering of the brood nest temps is conducive to Varroa reproduction,

The reason your getting several different answers is because the results of using it as a ventilation will vary from region to region.

The best way to determine if it is for you is to either get local advice or if not avaliable run some yourself and see, however do not make the same mistake some folks on this forum did years ago and have one good season switch everything over and the following season loose everything. 

So don't take the advice of a beek in England if you live in Texas or Maine if you live in Florida!


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## Zonker (Mar 10, 2010)

Yeah, the university research about the screen being good ventilation in the winter was from England, which is getting warmer but still doesn't match Virginia.

I'm a civil engineer and I deal with building insulation all the time. Condensation doesn't kill us but it does destroy our homes so in the winter we're fighting the same fight as the bees. Up north the vapor barrier is on the interior. Down south the vapor barrier is on exterior and here in VA you can't use a vapor barrier at all. I wish I knew the calories burned by a hive so that I could calculate exactly how much insulation/ventilation to apply and where.

I suspect (guess) that the bees don't produce enough heat to warm the exterior walls of the hive, which means the dew point is internal to the hive. Also the convection currents in the hive will equalize the temperature in the hive unless the walls are within roughly a 1/2 inch of the bees. So ventilation would be much more important than insulation (which is a bunch of guesses). 

Its like having thousands of tiny clients who never complain about the construction costs. Lots of fun.


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## angryhippie (Mar 11, 2010)

I decided to go ahead and do a screened bottom. I found some #8 hardware cloth at Ace Hardware for $3.50/ft.


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## Michael Bush (Aug 2, 2002)

Keep in mind that bees control their environment by evaporating water in the heat and by controling the ventilation. Too much ventilation will prevent them from being able to control it. A SBB at the bottom of a vertical hive is not a lot of exposed space. The length of long hive makes for more exposed area and may be more than the bees can account for.


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## Zonker (Mar 10, 2010)

How do the bees control ventilation? I assumed that I was completely in charge of the thermostat (which would come as no surprise to my wife). I'd hate to be working at cross purposes to the bees. Maybe if the bee's activities could be observed I could get a feel for how they felt about the conditions (sort of like customer feed back).


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## bigbearomaha (Sep 3, 2009)

> How do the bees control ventilation?


Propolis.

They will fill in cracks, crevices, etc... they need to , to prevent too much hair from coming in.

Big Bear


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## HBH (Oct 16, 2008)

Michael Bush said:


> The length of long hive makes for more exposed area and may be more than the bees can account for.


In my area (MD,VA), I have observed the need to close the bottoms up in late July or early August. If I do that, they can make it through the winter. If I don't - they die by starvation. I think they consume too much honey trying to control the temp of the hive when it starts getting colder.

On my Lang hives, I leave them open all Winter and don't see that as problem. As Mr. Bush mentioned earlier, I think it's a matter of too much ventilation being a bad thing.

One final thought - bees like it hot.


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## angryhippie (Mar 11, 2010)

Anyone from the Ohio Valley that has an opinion or some knowledge about SBB in our area?


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## Zonker (Mar 10, 2010)

I wonder if having the drafts blocked by the lang's shape makes having the bottom open ok. The bees in a TBH would have drafts on two sides.


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## Michael Bush (Aug 2, 2002)

There is not only the issue of cold in the winter blowing in through the screen. The bees are cooling the hive in the summer. If you leave your door wide open in the summer, can you cool you house? Bees cool the hive by evaporation but that won't work if they can't control the flow of air.


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## buckbee (Dec 2, 2004)

I wouldn't want to contradict what Michael says, and I think this is a matter of local climatic conditions: the more extreme your climate - i.e. the hotter the summers and the colder the winters - the more it matters whether there is a floor on the hive, and the greater degree to which bees need total control over the airflow.

My evidence is based on my own experience in the relatively mild and damp climate of south west England, where summer days rarely exceed 30 C and winters bottom out around -10 C and mostly stay above -5 C. Here I find that closed floors tend to create too moist an atmosphere in winter, and bees do better with open mesh. One of my strongest hives has no floor at all, and it has just come through its third winter, which was the longest and coldest for 30+ years. 

If your summer temps routinely exceed the normal brood temp of around 34 C, you may need to give the bees some help with air conditioning. Likewise, if you have very cold - and especially windy - winters, some control of floor-level ventilation may be needed, but I think you always need _some_ floor-level ventilation.


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## Zonker (Mar 10, 2010)

I haven't done any research , so everything I have to add to the conversation is strictly human structure data, so this may not be on any value, but ....

evaporative coolers only works in the desert. They don't even work in the Phoenix anymore because too many people are watering their yard. Also, whole house fans can lower the temperature of a house by 10 to 15 degrees (remember Grandma's?), so unless I had a heat pump I would cool my house by opening the front door.

Actually I've considered putting a chimney on the hive with a mechanical thermostat/damper (a spring expands and contracts as it warms or cools). With a tall enough chimney you could suck the bees right out of the hive. It would be interesting to calibrate the chimney height to provide the right current to keep the bees happy all summer.


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## twd8711 (Feb 2, 2008)

after i went to screened bottom boards i feel i see a much healtier hive, in florida it was mostly for mites and ventalation, that and cedar smoke from time to time seemed to keep mites in check, in penna i use them for ventalation in the summer and in the winter to help clean out bottom board, i made it so the board could slide out the back, didnt put bottom board in one of them over winter and it seems to be one of the stongest hives


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## buckbee (Dec 2, 2004)

Bees In Winter

The Principal Causes of Heavy losses.
How to Prevent Them. 

A goodly number of apiarists expressed
themselves concerning the cause and
prevention of winter losses of bees in the
columns of The American Bee Journal
recently. Professor A. J. Cook laid the
losses to poor food and severe cod and
suggested as a preventive good food
and good cellar or thorough packing.
*M. Makin believes that the principal
cause is dampness and want of ventilation
He says, "since I have given my
bees plenty of ventilation at the bottom
of the hive I lose scarcely any bees."*

The Cedar Rapids Evening Gazette
Tuesday, November 21, 1893 Cedar Rapids, Iowa

Thanks to Historical Honeybee Articles

(Please excuse partial xposting)


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## MIKI (Aug 15, 2003)

angryhippie said:


> I decided to go ahead and do a screened bottom. I found some #8 hardware cloth at Ace Hardware for $3.50/ft.


Now just be sure you have some type of drawer to close the whole thing in. at least then you have both opyions open or closed.


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## Sam-Smith (Jul 26, 2009)

The thing I did for ventilation was move the entrance to the top and drill 7x 7/8" holes along the bottom of my 48" hives, screened them and added wind baffle cleats to the outside, now when I change the follower board for hive sizes I actually scale the ventilation to. I'm hoping this will get my bees through the winter, I plan to insulate the outside topbars as well. My hope is that this will create a gentile convection airflow instead of a wind-tunnel.


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## Zonker (Mar 10, 2010)

I'm using screened doors on the bottom of my hives. They're cheap and easy to build, but best of all I can open them and dump out whatever debris has accumulated. If I want less ventilation (or if I want a new swarm to feel like it is in a safe place) I lay a layer of newspaper on the door and shut it.


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