# ventilation



## Rader Sidetrack (Nov 30, 2011)

Certainly there can be too much ventilation. Bees cool their hive by hauling in water to evaporate. That way they can get the hive temperature to be below the ambient temperature when its very hot. The process is similar to a swamp cooler in a house.

So if there is a constant flow of outside air through the hive (from an open bottom, for instance), that evaporative cooling process will be hindered, to say the least.

My TBHs have a top entrance, similar to this, with _no _other openings and that works where I am.


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## thylton48 (Dec 29, 2014)

Rader Sidetrack said:


> Certainly there can be too much ventilation. Bees cool their hive by hauling in water to evaporate. That way they can get the hive temperature to be below the ambient temperature when its very hot. The process is similar to a swamp cooler in a house.
> 
> So if there is a constant flow of outside air through the hive (from an open bottom, for instance), that evaporative cooling process will be hindered, to say the least.
> 
> My TBHs have a top entrance, similar to this, with _no _other openings and that works where I am.



Thanks that makes since. Evaporative cooling does not work well in our humid climate; I certainly don't want to hinder what little cooling they will get.


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## ruthiesbees (Aug 27, 2013)

here in coastal Virginia, we have a lot of heat and humidity. I run my top bar hives with screened bottom boards that are closed year round. (I let the junk fall through to the board and clean it off). My preference is to have white roofs and some afternoon shade if possible. I will also sometimes replace a 1/2 inch spacer bar with plastic screening at the top to allow some heat to pull out the top. My roof has a space between the bars to allow air to pass underneath and pull out some heat. There are also 3-1inch holes along the side that allow for some air movement, but not too much.


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## crofter (May 5, 2011)

There probably would be an optimum amount of air exchange needed to allow the evaporative cooling to work. As the water they haul evaporates it raises the relative humidity of the inside air as well as cooing the surface it evaporates from. With no air exchange the internal air would reach the saturation point and no further evaporation or cooling effect would take place. 

With too much air exchange when very high outside temperature occurs, the cooling effect may be swept away like air conditioning with all the windows open.

How much ventilation is enough and how much is too much? In my climate it is not a concern. I have noticed bees at one side of the entrance fanning in and at the other side fanning out! Hmmm? Maybe they have a game plan and we would screw it up by opening the hive too much.


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## dynemd (Aug 27, 2013)

I have seen many times screened ventilation holes in inner covers being propolized shut completely in the middle of summer heat. I was trying to help them stay cool, which was clearly contrary to their game plan. I've noticed that the bees are always right and it is often different from what I think best.


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## missybee (Sep 6, 2014)

We had screened bottom board, screened inner cover and tons of bees. They never tried to propolize the screen shut. Seemed to work for our hives.


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## Jon Wolff (Apr 28, 2013)

In summer, the bees will tell you if they need more ventilation by bearding around the entrance. If I don't see bearding, I leave them be. But too much moisture in the hive in winter is a killer, so some kind of ventilation through the cold months is also a good idea, just not too much. I use a ventilation top bar. It's simply a top bar with 3/4" diameter holes drilled along the length. The bottom side is screened and the top side is stopped with cork bottle stoppers. I uncork holes until the bearding disappears in summer. This winter I'm trying it for the first time and have it behind the follower board with just one or two holes open to see if that helps with reducing winter condensation (I didn't want a chimney effect of air coming in through the entrance and drawing heat straight out through the ventilation holes). The bees had taken a gallon of syrup late in the fall, and the observation window was fogged until I added the bar, after which it cleared up, so it seems to be working.


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## thylton48 (Dec 29, 2014)

Thanks for the replys; gives me a lot to think about.


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## Jon Wolff (Apr 28, 2013)

One other thing to consider regarding hive ventilation. There is a direct relationship between hive humidity and varroa mite reproduction. The higher the relative humidity in the hive, the lower the mite reproduction rate. You don't want to create an environment ideal for varroa by reducing the humidity through too much ventilation.


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## Rader Sidetrack (Nov 30, 2011)

Here is what one of Randy Oliver's pages says about hive temperature and humidity re varroa:


> Avoid shade and keep colonies warm and dry. There are several reports of colonies faring better against mites when kept out in the open. Rosenkranz (1988) found that varroa prefer relatively cool temperatures of 75-88°F, well below the central brood nest temperature of 95°F. Harris, et al. (2003) state that “research by others has shown that high temperatures and extremes in relative humidity within the broodnest of a colony of bees will reduce the number of varroa mites that lay eggs.”
> 
> http://scientificbeekeeping.com/fighting-varroa-5-biotechnical-tactics-i/


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## shannonswyatt (May 7, 2012)

missybee said:


> We had screened bottom board, screened inner cover and tons of bees. They never tried to propolize the screen shut. Seemed to work for our hives.


Missybee, what do you mean reguarding screen inner covers? I assume you are talking about Langs, not TBHs?


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## shannonswyatt (May 7, 2012)

Graham, I just read today were someone is trying to market a device that heats a hive up to about 103 degrees for two hours. It is supposed to damage Varroa, but the bees can handle it. Two treatments a year is supposed to do the trick. I had not heard that high heat affected Varroa before today. If it cooked the SHB at the same time we would be set!


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## missybee (Sep 6, 2014)

shannonswyatt said:


> Missybee, what do you mean reguarding screen inner covers? I assume you are talking about Langs, not TBHs?



opps in the wrong forum, yep langs.................so sorry


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## Rader Sidetrack (Nov 30, 2011)

Here is a USDA page on a study involving _heat treatment_ of varroa (on live bees):

http://www.ars.usda.gov/SP2UserFile...1-400/384-Harbo--Heating Adult Honey Bees.pdf


Note that the heat may result in the mites falling off the bees, but something like an oil tray is needed to actually kill the mites. Also, since this apparently only affects emerged mites (on bees), presumably multiple treatments spaced a week or so apart would be required to deal with newly emerged mites. (40 degrees C = 104 degrees F)


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## Apismellifera (Oct 12, 2014)

Hmmm... Why not use something like reptile heating mats? 

Not so easy if you don't have some protected space at the bottom of the hive to place such things. Used to keep reptiles so I have a thermo control that will take 3 devices plugged into it... Good to calibrate it against another thermo placed wherever in the hive it needs to be.

But I'm wondering what manipulating the hive temp does with brood, etc. If you up the temp seems like it could stimulate brood at times when it should be shut down?

Haven't read that paper yet, maybe some of this is there.


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## Jon Wolff (Apr 28, 2013)

Shannon, I've read that what's bad for varroa tends to be good for SHB and vice versa, unfortunately.


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