Insulation

[Gilberdyke John]

Good morning. I’m in South Wales, relatively new to beekeeping and I’ve only got 2 National hives (cedar). Thinking about insulation for winter - does anyone swap their sheet metal covered cedar roofs for deep poly roofs (from Abelo)? Is this a good idea or not? I understand 75% of heat is lost through the roof so an insulated roof is better than no insulation, but is the Abelo poly deep roof compatible with a cedar national? Thanks in advance - I have little experience with over wintering and rain/wet here is a bigger problem than low temperatures.

A simple question but it opens floodgates I've slowly migrated to abelo 14 x 12 /national polyhives. Prior to the changeover I made slip on rigid hive cosy's to use instead of wooden roofs. They kept heat in during winter and out in summer. Most were made out of 1" kingspan seconds joined with adhesive and pinned with skewers then joints sealed with adhesive foil tape. Maybe not as thermally effective as 2" or thicker but a vast improvement on a bit of traditional soggy carpet or foam sponge on the crown board. Waterproof and windproof too

 

[Nannysbees]

Good morning. I’m in South Wales, relatively new to beekeeping and I’ve only got 2 National hives (cedar). Thinking about insulation for winter - does anyone swap their sheet metal covered cedar roofs for deep poly roofs (from Abelo)? Is this a good idea or not? I understand 75% of heat is lost through the roof so an insulated roof is better than no insulation, but is the Abelo poly deep roof compatible with a cedar national? Thanks in advance - I have little experience with over wintering and rain/wet here is a bigger problem than low temperatures.

Where in South Wales are you?

 

[Amari]

Where in South Wales are you?

Yes, would be nice to know. SWMBO was born and bred in Pontllanfraith.....

 

[user 20297]

I have my own favoured method of insulating a beehive, but came across this interesting product webpage with step-by-step instructions and a fair amount of reasoned explanation.
They're obviously trying to sell a product and the technique looks a bit fiddly to me, with no guarantee that it works. Nonetheless, possibly a useful extra bit of guidance for some people?

https://low-e.co.uk/application/beehives/

 

[Goran]

Heh, this look more as insultation than insulation for bees.. Insulate them with food and no worries..

 

[user 6228]

Of you seal the ends, (which the instructions on the product say you should do), the still air in the flutes gives a slight increase in insulative properties.

Its intuitive to think that the ends need sealing for convection reasons. But its not the case at the temperature differences and gap sizes (a few mm and a few tens of degrees)we are looking at here. In a horizontal air space heated from below there is a critical combination of temperature difference and and air gap that has to be reached before convection currents start (Google Rayleigh number). Until its reached heat transfer is just conduction (and radiation) . Curiously the roof space above crown boards in standard design wooden hives is above that critical level. If only they had made the gap above the crown less than 10mm?
Our experience of the world of air and water doesn't scale very well downwards and we need to sometimes abandon our common sense. Think of the Gerry Anderson's Stingray and thunderbirds when they have waves and bubbles. They have to display the water movement in slow motion to make it look more realistic but it still doesnt.
Non-scalability of fluids

 

[user 20297]

Its intuitive to think that the ends need sealing for convection reasons. But its not the case at the temperature differences and gap sizes (a few mm and a few tens of degrees)we are looking at here. In a horizontal air space heated from below there is a critical combination of temperature difference and and air gap that has to be reached before convection currents start (Google Rayleigh number). Until its reached heat transfer is just conduction (and radiation) . Curiously the roof space above crown boards in standard design wooden hives is above that critical level. If only they had made the gap above the crown less than 10mm?
Our experience of the world of air and water doesn't scale very well downwards and we need to sometimes abandon our common sense. Think of the Gerry Anderson's Stingray and thunderbirds when they have waves and bubbles. They have to display the water movement in slow motion to make it look more realistic but it still doesnt.
Non-scalability of fluids

Since writing my thoughts there I have given up on any kind of transparent crownboard I favour of one made from 25mm PIR with a 6-8mm rim.
I don't see much practical advantage in seeing the bees in Winter as the view gives very limited information; ie. are they dead or alive?
In Winter, the lid I place above that crownboard is anything upto another 100mm of PIR, with 50mm PIR sides.

What is your thought on the closeness of fit of a deep lid or "cosy" that extends a good distance down the side of the hive. I've seen it written that this should be quite a loose fit as the refelective properties of the foil are nullified when they are in contact with the outer hive surface; if so, I don't understand the physics of that. It's also been suggested that with the narrow airgap thus created there is a reduced benefit if not sealed at the bottom. That seems logical but after what you have said previously, maybe not?

 

[Erichalfbee]

Since writing my thoughts there I have given up on any kind of transparent crownboard I favour of one made from 25mm PIR with a 6-8mm rim.

Do you have a photo?

 

[user 20297]

As all of mine are currently doing what they were designed for, I have this scrappy photo showing one that has what is technically too thick an edging strip at 9mm, but I haven't had a problem with brace comb. This one is also modified, with a removable, approximately 300 x 300 square for when I was playing with mini-plus hives last summer. This makes the crownboard into an adaptor plate.
25mm PIR is very rigid and using nothing more than PU sealant, the wooden border is very securely fixed.
The facing side to the bees has been left untreated and burrowing bees have not been a problem.
I have about half a dozen of these in active service.
I credit @derekm @Erichalfbee and others here as well as my own experience in house construction, for seeing the virtue and flexibility of PIR early in my beekeeping "journey".

 

[Erichalfbee]

As all of mine are currently doing what they were designed for, I have this scrappy photo showing one that has what is technically too thick an edging strip at 9mm, but I haven't had a problem with brace comb. This one is also modified, with a removable, approximately 300 x 300 square for when I was playing with mini-plus hives last summer. This makes the crownboard into an adaptor plate.
25mm PIR is very rigid and using nothing more than PU sealant, the wooden border is very securely fixed.
The facing side to the bees has been left untreated and burrowing bees have not been a problem.
I have about half a dozen of these in active service.
I credit @derekm @Erichalfbee and others here as well as my own experience in house construction, for seeing the virtue and flexibility of PIR early in my beekeeping "journey".

View attachment 35165

Thanks. Food for thought

 

[user 6228]

Since writing my thoughts there I have given up on any kind of transparent crownboard I favour of one made from 25mm PIR with a 6-8mm rim.
I don't see much practical advantage in seeing the bees in Winter as the view gives very limited information; ie. are they dead or alive?
In Winter, the lid I place above that crownboard is anything upto another 100mm of PIR, with 50mm PIR sides.

What is your thought on the closeness of fit of a deep lid or "cosy" that extends a good distance down the side of the hive. I've seen it written that this should be quite a loose fit as the refelective properties of the foil are nullified when they are in contact with the outer hive surface; if so, I don't understand the physics of that. It's also been suggested that with the narrow airgap thus created there is a reduced benefit if not sealed at the bottom. That seems logical but after what you have said previously, maybe not?

in a hive, when convection has established inside, the two areas of greatest rate of loss are top and the two sides that are at right angles to the comb. in addition elevated temperature buoyant air needs to be retained. Hence the PIR cosy that reaches down the sides to or even beyond the entrance, that has all of its seams inside and out sealed. This picture is from 2013. Radiation and hives big complex subject., lets put this way, Tom Seeley found bees wanted their nests in the shade, however it appears its not only to shelter from the sun.

 

[user 6228]

25mm may be ‘enough’ but 50mm will be better.

How do we know? Simple Physics would provide you with the answer. Double the thickness will halve the heat transmission.

For the OP, I made slightly deeper roofs than the standard Thorne offering. Each had 25mm of recticel under a 6mm sheet of ply. Roofs were covered with thin aluminium sheets. I still leave another 25 or 50mm sheet of EPS over the crown board (a 10mm piece of ply). Many remained in position all year round.

The standard roofs really require the roof to be held down, particularly though the winter if a 50mm slab is added. A concrete block is generally more than adequate.

Doubling the thickness doubles the roofs thermal resistance - agreed! but the increase in temperature close to the crown board causes the temperature to rise nearer the walls and so some of the gains are lost. So then you need to insulate the walls and seal that to the roof insulations as well. What happens next is the air next to the entrance and the floor mesh start to warm up and become buoyant and escape. To combat that you need to make the distance from the top of hive to entrance bigger and /or make the hydraulic resistance of the entrance greater by making it smaller and/or increasing its length (tunnel entrance).

And so on..
ohh we have forgotten that these thermal resistances are in series with the thermal resistance of the air cavity.
This is influenced by the hydraulic drag of the narrow gap between combs and bees obstructing them. This means the effect of the added insulation is relative to these resistances.

In short its complicated, but to get more out of your insulation than a simple roof insulation slab you have to get canny and the bees have a 600,000 year head start.

 

[Garry R]

I have wood floors and poly boxes deeps in winter and poly supers during summer. Winter and summer I have solid wooden crown boards with wooden roofs lined inside with 50mm polystyrene for insulation and tacked onto the inner roof wood with a few spots of non solvent adhesive and no silver foil.