# Another question



## SteveStevenson (Feb 14, 2014)

New beek here again with another question. Should I put a screen as the bottom of the TBH I'm making? I'm in Alamama so it gets hot but at the same time it went down to 10 degrees this past winter. If use screen do I need to cover it in the winter?


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## Rader Sidetrack (Nov 30, 2011)

If you choose to put a screen bottom in your TBH, do it for reasons other than ventilation. Bees use a form of evaporative cooling to keep their hive at an appropriate temperature. They do this by carrying water into the hive and allowing it to evaporate. If the bottom is wide open, the _lowest _the hive temperature can be is the ambient air temperature.

Bees keep their brood at 93-95 degrees. If ambient air temperature exceeds that, and the bees can't use evaporative cooling, that will not be pretty.


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## ruthiesbees (Aug 27, 2013)

Mine has a screen and I like it, not for any ventilation, but it lets stuff drop down on the IPM board so I can trap the larvae of the bad bugs. I left my IPM board on the hive all year, and I even stuffed the blue insulation up underneath when we got the cold temps in Jan.

One other thing to consider is an observation window in your hive. (it will make the wife happy)


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## wolfster101 (Feb 18, 2014)

Rader Sidetrack said:


> If you choose to put a screen bottom in your TBH, do it for reasons other than ventilation. Bees use a form of evaporative cooling to keep their hive at an appropriate temperature. They do this by carrying water into the hive and allowing it to evaporate. If the bottom is wide open, the _lowest _the hive temperature can be is the ambient air temperature.
> 
> Bees keep their brood at 93-95 degrees. If ambient air temperature exceeds that, and the bees can't use evaporative cooling, that will not be pretty.


Curious, if this is so, why do so many use the screened bottom board? Aside from the IPM aspects anyway. I am building my first Warre hives and planed to use screened bottoms. Can you elaborate more on this?


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## Rader Sidetrack (Nov 30, 2011)

> if this is so, why do so many use the screened bottom board? 

I can't tell you _why _other people do what they do. Why millions of people buy lottery tickets - with an average payback of about *40% *on each dollar - is a mystery to me too. :s

I didn't say that IPM systems have no value. I simply said that using an _open _screen bottom for cooling a hive is _counterproductive _to the bees own evaporative cooling efforts.

I have screens built into my Lang hives, but they are used with _closed _bottoms and oil trays to kill whatever gets through the screen.


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## wolfster101 (Feb 18, 2014)

> Bees keep their brood at 93-95 degrees. If ambient air temperature exceeds that, and the bees can't use evaporative cooling, that will not be pretty.


I am curious how the bees in the south handle this. When I lived in UT we used swamp coolers because the humidity was so low but now I, along with the OP am in the south and there is no such thing as evaporation in this incredibly humid environment.


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## Rader Sidetrack (Nov 30, 2011)

wolfster101 said:


> I, along with the OP am in the south and there is no such thing as evaporation in this incredibly humid environment.


I believe you will find that evaporative coolers are successfully used to cool greenhouses in North Carolina. This document suggests that appropriately sized evaporative coolers could be reasonably expected to drop the temperature 12 degrees in July in Concord NC:
http://faculty.caes.uga.edu/pthomas/hort4040.web/Carolina Cooler SpecTech sheet.pdf


You can even test it yourself, on a small scale. Use a spray bottle to mist water on your face on a hot day and report the results.


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## Michael Bush (Aug 2, 2002)

If it is screened and not blocked a package is likely to abscond. And if it's wide open, as already pointed out, it may keep them from being able to cool the hive. In my experience it does little or nothing for Varroa. It just makes things more complicated. I built some with screens. I never do anymore...


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## wolfster101 (Feb 18, 2014)

> You can even test it yourself, on a small scale. Use a spray bottle to mist water on your face on a hot day and report the results.


I have. When I first moved here I had a genius idea to create a misting system on the back deck. When turned on, instead of cooling as I was use to out west instead I just got wet. It takes a dry environment to cause evaporation. Apparently the bees have a better grasp on this then I do.


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## Rader Sidetrack (Nov 30, 2011)

I agree that North Carolina or Tennessee is generally more humid than say Arizona in the summer. And I cannot say what the humidity was when this study was conducted in Ohio. But you can clearly see that the bees were able to maintain their brood nest at a temperature significantly lower than the surrounding ambient air: 
http://library.uniteddiversity.coop/Beekeeping/hive_temperature.pdf

The hourly chart (page 186) show outside temperatures over a 24 hr period varied from 68° F to 108° F, while the temperature in the brood area varied from 92.8° F to 94.1° F. The test hive was in the shade. The experiment was at Ohio State University, Columbus, Ohio.

And the excerpt starts on page 181, so you don't have to wade thru hundreds of pages to see the chart.


One more thing - I see huge commercial [chicken] broiler houses on farms scattered all over the South that are cooled with evaporative cooling misting systems. _Somehow _it works!


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## Wolfster (Aug 5, 2013)

> If it is screened and not blocked a package is likely to abscond. And if it's wide open, as already pointed out, it may keep them from being able to cool the hive. In my experience it does little or nothing for Varroa.


MB, do you mean a completely open bottom? And what about SHB? I noticed in my hive last year the little buggers would run from the bees and fall to the bottom and hide in the corners or any crack small enough. I figured with a screened bottom they would at least fall out of the hive.

If you think there is no real use of the SBB then I guess I will have to rebuild my bottoms and trust completely in you and 'ol Mr. Warre. 

Thanks for the advice!


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## Michael Bush (Aug 2, 2002)

>MB, do you mean a completely open bottom?

I would never have a completely open bottom. 

>And what about SHB?

On good reason not to have a completely open bottom...

> I noticed in my hive last year the little buggers would run from the bees and fall to the bottom and hide in the corners or any crack small enough. I figured with a screened bottom they would at least fall out of the hive.

No, they will just hide below the screen or fly up and crawl in the screen. Hard for the bees to guard an huge screened area that is big enough for small hive beetles to get through...

>If you think there is no real use of the SBB then I guess I will have to rebuild my bottoms and trust completely in you and 'ol Mr. Warre.

As long as you put a tray in, they are ok. If you don't put a tray in, it's too much ventilation in a top bar hive.


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