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When the temperatures are high and the heat indexes are as well, do y'all ever pull the plastic oil trays and leave just the screened bottom to help cool the bees. Index have been high 90's to low 100's all week. Whether you use the plastic oil trays or the aluminum trays for your screen bottom board can you give the bees relief from the heat by doing this and the bees be ok with just the screen. I don't imagine they will have cold issues or should I just prop the top more to let heat out? Thanks for any advice on cooling them down.
 

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The weather has been hot here in southern California and I use Ultimate Hive Covers that allow ventilation underneath. I thought I would increase to hive ventilation by drilling nine 2 inch holes and placed them on the hives after screening the holes over. Within a week all the hole were closed with propolis. I had also made some inner covers with clear lexan and drilled around 100 small holes in four groups to provide some ventilation, these were also sealed shut with propolis. Now I am careful not to jump to the conclusion that more ventilation is better. Maybe they are trying to keep the cool air in.
Ultimate.png Ultimate Top.png
 

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My SBB are always open, even in the winter. Ventilation is also very important in the winter because of potential condensation.
 

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I also use these covers and am very happy with them.
They have both 10 and 8 frame versions along with a very nicely priced screened bottom board.

Me to.

I also use the Honey Run All Season inner cover on my 12 hives, which has a hole the size of your fist in it for ventilation. The bees have never tried to close or reduce these holes. I guess it all depends on your bees and your locale.

http://www.honeyrunapiaries.com/store/all-season-inner-cover-p-232.html
 

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A constant flow of air in hot weather through an open screened bottom may work against the bees own efforts at keeping the hive cool.

From the USDA Agricultural Research Service ....
Bees store their food and raise their young in the honeycomb nest. Honeycomb is made from beeswax, which is secreted by young worker bees, and fashioned into the familiar honeycomb hexagonal shape. Because bees live in these wax combs, though, they have to keep the nest at a constant temperature, not only to keep the colony from overheating, but also to prevent the wax from melting. [HIGHLIGHT]In hot weather, bees cool the colony much like your swamp or evaporative cooler does - by evaporating off drops of water. Bees collect water and spread it throughout the colony in droplets. Then they fan the air to create an air stream over the water drops, causing the water to evaporate and thus lowering the nest temperatures.[/HIGHLIGHT]

http://www.ars.usda.gov/research/docs.htm?docid=11067&page=7
My hives do have screened bottoms, but they have oil trays beneath them and airflow through those screens is blocked year-round. My hives have top entrances.
 

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Somehow the moisture that the bees put in the surrounding air has to get out of the hive. The SBB allows that to happen.
 

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A constant flow of air in hot weather through an open screened bottom may work against the bees own efforts at keeping the hive cool.

From the USDA Agricultural Research Service ....
Not sure I see the connection. The reference only mentions the evaporative cooling and need for air stream to effect that. I don't read from that the the open bottom gets in the way of that process and it seems to me that the addition of a top entrance/vent that you'd achieve the air flow. But maybe not. Would be interesting to see empirical data on hive temps and humidity with and without open bottoms.

As an aside, is it just generally accepted that SBB = Screened Bottom Board and not Solid Bottom Board? What a horrible use of an acronym.
 

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> A constant flow of air in hot weather through an open screened bottom may work against the bees own efforts at keeping the hive cool.
Not sure I see the connection.
Since the ARS quote mentioned a swamp cooler, lets use that to illustrate the connection. :)

If your house was being cooled by a swamp cooler (or air conditioner) would you be better off having all the windows of that house open or closed? :rolleyes:

Certainly the moisture laden air in the hive needs to be expelled from the hive in order for further evaporative cooling to take place, but a constant breeze flowing though that screen may overwhelm the bees efforts at evaporative cooling. I let the bees control the airflow by fanning when they feel it is appropriate.


> you need an opening in the top (entrance, vent, etc.)?

Yes, as I said in my earlier post, my hives all have top entrances.
 

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>
If your house was being cooled by a swamp cooler (or air conditioner) would you be better off having all the windows of that house open or closed?
Not a direct analogy, but I get your point, I would not want to drill holes all over my hive. Got it. For the swamp cooler to work, you need water and air flow. I don't see that the referenced article is suggesting that an ScBB is contrary to achieving air flow. If it does inhibit a proper air flow over the water source, then agreed, not a good idea. If it creates an air flow, then great, shouldn't be a problem. Would love to see a direct reference for it either way.

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> you need an opening in the top (entrance, vent, etc.)?

Yes, as I said in my earlier post, my hives all have top entrances.
Hmm ... out of context and in response to a different post directed to a different person.
 

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> I would not want to drill holes all over my hive.

I certainly don't drill holes in my hive bodies. You can achieve a top vent / top entrance by manipulating the lid/cover instead of drilling holes in the hive bodies. Adding shims to the lid is one approach.

My lids are migratory style lids, but they have 3/8" thick wood strips glued to the underside of the perimeter of the plywood lid on 3 sides. The opening is formed by 'no shim' on the 4th side, which provides an entrance. If you prefer outer cover tops, I have seen reference to popsicle sticks being used to prop up the cover to create top vents.




>
I don't see that the referenced article is suggesting that an ScBB is contrary to achieving air flow.

The other references to screen bottoms that I find at the ARS site are in connection with "sticky boards". Here is one:

The screen insert works by creating a 1- to 2-inch gap between the bottom board and the hive bottom. The insert's wire mesh allows the mites to fall through the screen and onto the hive bottom so they can't reattach to the bee. Monthly samples of the fallen varroa showed that the screen insert reduced the mite populations by about 15 percent. Though not sufficient alone, the Beltsville screen insert can contribute to integrated pest management practices.

http://www.ars.usda.gov/is/AR/archive/mar00/bees0300.htm

Presumably access to those semi-permanent sticky boards by the bees is blocked by the design/construction of the bottom board, otherwise the bees would also be getting stuck on those sticky boards.

So my conclusion is that those ARS hives have screened bottom boards (above the sticky boards) but ventilation through the screen is closed off by the bottom board design.

.
 

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I use SBB and top entrances all year, in very hot weather I feed weak sugar water 1part sugar 2 parts water, they have to evaporate this by fanning air across it therefore cooling the hive, the moist air being heavier will fall out the bottom creating a vacuum which pulls the dry air in through the top. In my area this would be during our summer dearth, I think it keeps the bees busy and I have less robbing problems ( as long as I keep the community feeder away from the bee yard ) JMO
 

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The other references to screen bottoms that I find at the ARS site are in connection with "sticky boards"
Right, so pretty much my point. The reference provided in support of the assertion that screened bottom boards work against the bees efforts to cool the hive, really doesn't provide that support. Which isn't to say the assertion is incorrect, just not supported by that particular reference. I'd still like to see some good data.
 

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The other references to screen bottoms that I find at the ARS site are in connection with "sticky boards"
Right, so pretty much my point. The reference provided in support of the assertion that screened bottom boards work against the bees efforts to cool the hive, really doesn't provide that support. Which isn't to say the assertion is incorrect, just not supported by that particular reference. I'd still like to see some good data.
 

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And they all die with human intervention. Surely you are not suggesting if all humans died out that all bees would die out?
 

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I use SBB and top entrances all year, in very hot weather I feed weak sugar water 1part sugar 2 parts water, they have to evaporate this by fanning air across it therefore cooling the hive, the moist air being heavier will fall out the bottom creating a vacuum which pulls the dry air in through the top. In my area this would be during our summer dearth, I think it keeps the bees busy and I have less robbing problems ( as long as I keep the community feeder away from the bee yard ) JMO
Contrary to this popular misconception moist air which is really just water vapor in a little bit air is less dense than dry air.
Water vapor molecules, which are roughly one oxygen atom with a weight of 16 and two hydrogen atoms each with a weight of 1, add up to a molecular weight of 18, which is much lighter than the nitrogen (14) and oxygen (16) = 30. Water molecules displace the dry air molecules when they evaporate into air.
 
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