[ThunderboltFarm]

I am new to beekeeping and constructed my first horizontal Langstroth hive. I am in the process of making design modifications before I build my second hive this week. I have been researching ventilation and moisture control, a lot, and feel like I am going in circles. Any help on the questions below would be greatly appreciated. Below is a side view of the lid for my current design. Based on my research I think insulating the lid is a good idea (2-inch XPS insulation). In addition, I am planning on a second layer of insulation on the top boards during winter. Please note I am in north central Oklahoma. We have hot summers (>100 oF), some years are very dry and others are humid, and we can have short periods of colder temperatures in the single digits (Fahrenheit).

Note: metal roof not shown

Lid Ventilation Holes?

Should I add two 1-inch ventilation holes (one on each end) to the lid? How big a vent is enough but is not too much? In the summer, will the ventilation holes help remove hot air or provide a path for hot air to enter? Is 2-inches of insulation enough to not have ventilation holes?

In the winter, by insulating the top of the hive, condensation should occur on the sides and bottom of hive. Is there any need to have a ventilation hole in the lid to remove any moisture build up during the winter?

Bottom Board Insulation?

Is insulating the bottom boards a good idea? The beetle trays would be removed and replaced with a PVC sheet with a one or two-inch thick piece of insulation glued to it. This will result in a screened bottom with a 5/8-inch gap to the insulation based on my current design. Will this create an area to build up unwanted junk and can this be a safe haven for bugs during the winter transition periods? Also, should there be a drainage hole in the insulated bottom board?

For those that have beetle trays in place during the winter, do you keep mineral oil in the bottom year round?

 

[Cariboospeed]

From what I've learned from my horizontals, at least a 2" hole in each end for ventilation. I have one that's bearding a bit during the day, and I put a little stick under the lid to make a 1/8" gap. (It has 32 deep frames and another 20 meds). The other, (32 deeps) seems ok in the currant 30*C+ temps. Both have 3 - 3"x1/2" entrances on the long side (front).
I used 1.5" insulation between 3/8" ply, 1" polystyrene for the bottom. Hinged lids, 1" styrofoam under ply.
If I build another, I'd definitely make it like the larger one that holds 32 deeps, and can take med. supers on top, and the lids closes over it all. Capacity is awesome.

 

[viesest]

I have been researching ventilation and moisture control, a lot, and feel like I am going in circles. Any help on the questions below would be greatly appreciated.

A schema for insulation, circulation, condensation and ventilation.

 

[BW56]

I'm in Phoenix Arizona. 115*+ this week. When I built my horizontal hive (my one and only hive) I made the roof way over-sized with a 1" gap in the overlap at the peak. Allowing hot air to exit at the peak between the overlap drawing in ambient air under the eaves. Three inch screened vent in the floor near front quarter of hive and another near the top of the back wall. So far so good. No bearding. Time will tell this winter. Since May they have built and are filling ten combs (Top bars only) and working on building numbers eleven and twelve. Ill add two at a time moving the follower board with the same vent as the back wall when ready up to twenty or so bars. I love the covered inspection window on the long side. Great for a quick noninvasive look.

 

[ThunderboltFarm]

Thank you everyone for your feedback!!!!

As it relates to the lid design, I think adding ventilation holes is counter productive for heat loss/gain. It will be better to seal the top air space in the lid and insulate it well. The bees propolize the gaps in the top slats and seal it off from the lid air space anyway. During the winter, if condensation does occur between the lid and the top slats, I think putting in polyester blanket to absorb the water should do the trick. Can I check if condensation was an issue in the winter by checking the blanket for moisture in the spring?

On a side note, I currently have screened ventilation holes in my top slats, which the bees have propolized and sealed completely.

vieset, the schematic you gave is for an uninsulated lid top, which is different from what I am proposing. However, thank you for your help!

For the bottom, I think adding 1-inch XPS is a good idea for the winter. 2X lumber (1.5" thick hive sides) has an R-value of about 2.1 and 1-inch XPS has an R-value of 5. With a well insulated lid, the condensation should occur on the sides of the hive.

Thoughts?

 

[ThunderboltFarm]

I'm in Phoenix Arizona. 115*+ this week. When I built my horizontal hive (my one and only hive) I made the roof way over-sized with a 1" gap in the overlap at the peak. Allowing hot air to exit at the peak between the overlap drawing in ambient air under the eaves. Three inch screened vent in the floor near front quarter of hive and another near the top of the back wall. So far so good. No bearding. Time will tell this winter. Since May they have built and are filling ten combs (Top bars only) and working on building numbers eleven and twelve. Ill add two at a time moving the follower board with the same vent as the back wall when ready up to twenty or so bars. I love the covered inspection window on the long side. Great for a quick noninvasive look.

BW56, I think your idea for summer ventilation is excellent. It is like a house attic with a ridge vent allowing natural convection to keep the air below the lid at ambient temperature.

Note that the design I am proposing is trying to keep the temperature of the air below the lid at the average daily temperature (day and night).

 

[little_john]

I've no idea whether this will be of any interest to you - but here goes ...

The logic behind this system is that during the season the bees have the full run of the hive, and - being fully mobile - they are then well able to control conditions within the hive themselves by fanning/evaporation of water and so on. Top insulation is left in place to help stabilise the internal temperature.

Then - prior to the onset of Winter - the frame-count is reduced in size (as shown above), and centralised between a pair of divider boards, which essentially creates "a hive within a hive". A very gentle flow of air is created along the floor of the hive by means of openings at either end of the box, due to one being higher than the other. Heavy moisture-laden air, which normally sinks to the bottom of the hive, pooling there and causing the formation of black mould (or falling clean out of the box through an Open Mesh Floor, as at present) is, instead, carried out of the hive on this gentle current of air. Meanwhile, heat from the cluster is retained between the divider boards and underneath the substantial layer of insulation.

This is not 'just' theory, but the principle of a method revealed to me by Greg, who learned of this technique from watching Ukrainian/Russian videos of those who employ it. My only significant (perhaps ?) detraction from their proven method is in my use of a non-permeable Crown Board (Inner Cover). But - if any unforseen problems should arise as a result of this modification, then I'll revert to adopting a permeable covering instead - but this of course would then require some means of ventilating the roof-space.

The current status is that a colony of bees has just been installed into a purpose-made Long Hive, and the forthcoming Winter will be the first (for me) of trying-out this technique - so although I believe this to be a very clever method of ventilating a beehive whilst not losing heat from the cluster, I'm not yet able to confirm that it works as intended. But - I have every faith that it will.
LJ

 

[viesest]

With a well insulated lid, the condensation should occur on the sides of the hive.

Thoughts?

If for some reason you don't want condensation on top and bottom sides, but rather on front and rear sides just turn that schema for 90°.

There is a word "insulation" on schema why you say lid is uninsulated?
The principle is that insulation is not tight and warm humid air can circulate into cold space meant for condensation.
In that way condensed water is outside of brood chamber.

Edit: When posting I didn't read LJ post, but that's the same principle.

 

[ThunderboltFarm]

If for some reason you don't want condensation on top and bottom sides, but rather on front and rear sides just turn that schema for 90°.

There is a word "insulation" on schema why you say lid is uninsulated?
The principle is that insulation is not tight and warm humid air can circulate into cold space meant for condensation.
In that way condensed water is outside of brood chamber.

Edit: When posting I didn't read LJ post, but that's the same principle.

viesest, I am sorry, but I do not totally follow your response. My understanding is that you want to avoid condensation dripping on the bees during the winter. Thus, preventing condensation above the bee is the primary concern. Thank you for helping me understand how these systems work!

 

[ThunderboltFarm]

LJ, thank you very much for your response! I really like the idea of ventilating the hive and shielding the bees from the draft used to remove moisture from the hive during the winter.

LJ

CORRECTION - moist air is lighter than dry air, sorry.

Below is a psychrometric chart that may help with the discussion.

What is the driving force or gradient to move the air from the opening to the exhaust outlet?
1. Convection (temperature gradient, i.e. thermal buoyancy)
2. Pressure (wind or barometric pressure difference)
3. Air density via moisture content (humidity) difference
4. ??? What did I miss?

 

[viesest]

viesest, I am sorry, but I do not totally follow your response. My understanding is that you want to avoid condensation dripping on the bees during the winter. Thus, preventing condensation above the bee is the primary concern.

Not just above the bees but to prevent completely condensation in brood section. When air is relatively warm relative humidity is below condensation point. By circulation of that air to colder space relative humidity increases (as air is cooled down) and water (vapor) start to condensate. Water outside of brood section is not a problem. For example, LJ's drawing has this property; brood section is isolated and warm and colder space is at bottom side and between insulation and front wall.

Maybe I should write why I prefer box for insulation/condensation on top side. Warm humid air naturally wants to go upward, so that side should be considered for condenser. The other reason is feeding in spring. There is nice space for inserting food (fondant) and because in spring it is still cold that food is more easy accessible to bees, again because upper space is heated with flow of warm air.

 

[GregB]

.....

As I evaluate the proposed design, I am unsure if a higher elevation "exhaust" hole and lower elevation "entrance" hole is the best. Moist air is heavier than dry air, and thus if you want to move dry air into the hive, pickup moisture and then remove the moisture, ....

Incorrect.
Check your facts and redo.

 

[Gray Goose]

To add water molecules to the volume, we must remove other molecules to conserve the total number of molecules in the volume. Dry air consists mostly of nitrogen and oxygen molecules, which weigh more than water molecules. ... Therefore, moist air is lighter than dry air if both are at the same temperature and pressure.

so in winter cold dry air could come in the bottom hole, and the warm moist go out the top, as long as we do not dry the cluster out , it should work, hole Diameter may be used to calibrate the flow a bit. or equalise the hole height, would also modulate air flow speed.


GG

 

[little_john]

Part of the problem with discussing the mechanism(s) involved here, is that they involve complex and competing forces.

Moist air is heavier than dry air, and thus ...

Well, actually that's not the case. If you compare the molecular weight of water with those of oxygen and nitrogen (the major constituents of air), you'll quickly find that the more H2O that's present, the lighter becomes the overall mixture.

When I wrote "Heavy moisture-laden air, which normally sinks to the bottom of the hive ..." I didn't mean it was heavy because it was moisture-laden, but rather it was heavy and it was moisture-laden.

So - there are basically two competing dynamics at work: warmth and moisture - both of which will cause air to rise; and cooling (from the action of evaporation) which makes air denser and thus heavier, together with an increase in Carbon Dioxide, which together will cause air to fall. There's also the possibility that condensation could be involved.

So rather than argue which of these dynamics will 'win' over the other, I much prefer to adopt the view that - in practice - moisture can be removed from a beehive either in an upward or downward direction. (FWIW - my own pet theory is that cooled moist air begins it's journey in a downward direction, but if it cannot freely escape the hive it then becomes warmed, at which point it begins to rise. Others argue that it initially rises, cools - even condenses - and then falls.)

Whatever the truth of the above, black mould is certainly seen on and around the floors of poorly ventilated hives as a result of moisture collecting there - so for me, that's my starting point. The question then becomes "how to get rid of that moisture without compromising the cluster's warmth ?"

What is the driving force or gradient to move the air from the opening to the exhaust outlet?
1. Convection (temperature gradient, i.e. thermal buoyancy)
2. Pressure (wind or barometric pressure difference)
3. Air density via moisture content (humidity) difference
4. ??? What did I miss?

Air will move in an empty box with holes so made - presumably due to the warmth of the day contrasted with the cool of the night. Slight thermal leakage around the (right-hand) divider board - even a few degrees would be enough to cause a gentle current. So - a slight thermal gradient would be my favourite guess. Then add some lighter air from the moisture content as the air passes though - it all helps.

There's also a possibility of the Venturi Principle at work here too - with the exhaust being smaller than the inlet, causing some acceleration of the gas. Maybe.

You raise good questions. But that air does move through the box is not in dispute(*) - as luckily others have established that this principle does work in practice. Whether we now need to understand how it works, I would happily leave to others to determine.
LJ

(*) I'll feel a lot more confident making such an assertion after I've seen for myself next Spring that this system has worked over the coming winter.

 

[Gray Goose]

LJ,
How do you determine that/if "too much " moisture is removed?

seems I have had large hives winter with out upper entrance.
My only concern is the "air flow" 1 removes too much moisture and 2 too much heat.
the heat loss would require more stores and have the need for more waste removal (mid winter flight)
the moisture loss can effect brood start up. IMO

GG

 

[bushpilot]

Just joining the chorus, saying moist air is indeed lighter than dry air, all else equal.

I've seen the "heavy moist air" falacy in the bee magazines as well.

Clouds are generally "up" for a reason.

 

[ThunderboltFarm]

Incorrect.
Check your facts and redo.

oops, you are correct. Thanks!

 

[little_john]

Clouds are generally "up" for a reason.

Thanks to the sun of course. Don't leave your washing out on the line during the night ...

Dew on the grass in the morning etc.
LJ

 

[little_john]

LJ,
How do you determine that/if "too much " moisture is removed?
GG

Good question. Seems to me that we're immediately back into that "all beekeeping is local" issue again. With the method I'm testing-out with this new hive, a lot will depend on the humidity of the air entering it. If you're in snow and ice country, then your air will be fairly dry. In my neck of the woods the RH in mid-winter can often be upwards of 90%. Big difference.
Some folks seldom see a mid-winter flying day - around here they're very common, or have been the last few years. In fact, we've been having far too many of them - the bees never get to settle, and they chomp their way through stores like school-boys in a sweet-shop (candy-store).

I've made provision for regulating the exhaust flow -and thus control the whole thing - but yes, I agree: right now I have absolutely no idea of how to determine the need for any regulation. Classic 'suck it and see' in action.
LJ

 

[ThunderboltFarm]

I agree and understand now about the natural cross ventilation and movement of air and moisture from the bottom entrance (or opening) to the higher exhaust port. Thanks to everyone.

I just got my Dr. Leo book "Keeping Bees with a smile". I immediately turned to the winter moisture section. He claims there are two methods to remove the winter moisture.

1. Remove moisture with cross ventilation

Method 1 - upper and lower openings (LJ Method. Note Dr. Leo recommends insulated follower boards. Good idea!)

Method 2 - bottom ventilation slot

Method 3 - making a bypass to move moist bottom air to the outside.

Note: he likes method 2 or 3 to avoid drafts

2. Leave the moisture in the hive

Add hygroscopic material inside the hive to absorb water. He claims many researchers believe this is the most promising method by minimizing heat loss. I assume today we would use silica gel. Assuming silica gel can hold 40% of its weight in water and a typical hive respires up to 3 gallons of water in a winter, you would need about 7.5 lbs of silica gel for a hive. Thus, I would use 10 pounds. Please check my numbers on this.