Oh No! Not Matchsticks Again?

[Sayle]

That's Derek's PhD papers into the shredder then, poor dab

Nothing so dramatic. Every insulator's thermal conductance varies with temperature - it's just PIR board bucks the usual trend of insulation becoming more effective the colder it is, rather than less. Personally I like wool because it can handle moisture, won't decay over time, and won't outgas. Also I can trivially cut holes in it to make space for feeders and make unusual shapes. Also less fussy to use. You really don't want to be cutting celotex without a respirator.

 

[Gilberdyke John]

I'd certainly be interested in what your insulation is! One thing that I've noticed a lot of people saying that they are using (or would use given the chance) is kingspan/celotex, but something that I don't see mentioned at all is the major disadvantage of this: polyisocyanurate (the chemical the celotex foam is made from) begins to rapidly lose its insulative performance when the temperature drops below 15C! When you want your bees to be at their most comfortable and toasty compared to the outside is when celotex is performing at its worse. Compare this to something like plain-old sheep wool which works fine at whatever temperature (and if it gets wet it can dry out: bonus!).

In terms of insulation though, the girls went through this winter with 50mm of wool in the walls and floor (it's a DIY hive, timber interior and marine ply exterior), and as many layers as I could get in the top given that trees provide effectively infinite vertical insulation and that's where 75% of the heat goes.

As an interesting aside, the DIY hive uses a solid floor - about six inches below the mesh. Varroa can't climb back up (or at least most of them don't, though don't ask me to hunt down the paper in question) after falling more than a few inches and it also prevents humidity and temperature losses through the bottom. I never saw any condensation on the (transparent) coverboard when I checked during winter, though opening the inspection tray space below the mesh showed plenty of water was circulating since the floor was wet. Presumably it all condensed on the colder walls where the bees could use that lukewarm water for whatever they liked.

Sorry, something of a tangent there. But yes, the idea that the bees would kill themselves with hypoxia (?!!) because of no ventilation is rather strange. They have an entrance to provide fresh air.

Have you data from kingspan to back up your claims about the change in performance at 15 degrees C?

 

[Sayle]

Have you data from kingspan to back up your claims about the change in performance at 15 degrees C?

I have data on polyisocyanurate in-general two posts down from the one you quoted as well as more specific numbers on the performance loss (and whether it substantially matters: it doesn't).

 

[Apiarisnt]

Have you data from kingspan to back up your claims about the change in performance at 15 degrees C?

https://www.greenbuildingadvisor.com/article/cold-weather-performance-of-polyisocyanurate

 

[Amari]

nothing like the feel of wool against the skin..........

The Welsh have much in common with New Zealanders....

 

[pargyle]

Oh, polyisocyanurate is a great insulator! It's got great performance. Just...when it isn't too cold. Which is fine when it's got a nice thick brick wall between it and the outside and you've got the heat trapped in the house to keep it going. But if you've a thin layer of ply over it (or, god forbid, just strapped it to the side of the hive) you can bet it's flipping cold and not doing the best job it could.

That said, some is better than nothing. It goes from a fantastic insulator to a good insulator, but it's at least still an insulator. It's just the performance loss related to its temperature isn't something I see mentioned when people enthusiastically advocate for it. It's very convenient having a solid board to just slot in rather than something compressible like wool, after all. Cheaper, too!

I'd be thrilled to have someone come in and say that I've misidentified kingspan's PIR boards/celotex as being polyisocyanurate like a numpty, though, don't get me wrong. Or that I'm just wrong about the temperature affecting it in general! My information might be fruit of the poisonous tree. But I'm speaking from my layman's understanding at present.

PS: I should clarify that I'm talking about performance reduction in the 10-20% range, so it's still a decent choice.

PS2: Graph of performance here. It becomes less effective as an insulator quite notably at below the 4C mark. But again, we're not talking a 50% drop or anything here. It's quite 'mild'. But it is a property of the material that exists. I just ended up going for a sheep wool/fibreglass blend that I knew wouldn't degrade with age and could handle moisture just fine. Also means I can put a feeder in the top and just drape the wool blankets over it in the roof space! Obviously I have an Opinion, but I'll certainly not say you shouldn't use Celotex/Kingspan if its the most convenient option. I have the blessing of disposable income and time to tinker with financially sub-optimal hobbyist hive builds. If you're pressed for time or money but still want to insulate, sure, slap some insulation board on the sides and top of the hive. It's better than nothing!

View attachment 24965

Ahhh ... but ..for those of us with poly hives and poly roofs there is an insulation layer in situ as well as the PIR. The majority of those with timber hives will also have the PIR under the roof and next to the crown board so again there is an external layer before you get to the PIR.

I'm not arguing with the information you have provided but ... from a simple practical viewpoint I've put my hands on a polycarbonate crown board with 50mm above it when the exterior temps are near freezing and there's a heck of a difference between the heat retained there and that when a crown board does not have insulation above it.

You quite rightly make the point that a tree nest has the maximum of insulation above the brood nest and I would concur and say that 50 - 100mm of PIR above the crown board is a near as we can get to replicating that. I am watching, with interest, a company that is already experimenting with compressed sheeps wool for insulation purposes and that may be a competitor in due course for Kingspan/Celotex.

 

[Erichalfbee]

I am watching, with interest, a company that is already experimenting with compressed sheeps wool for insulation purposes and that may be a competitor in due course for Kingspan/Celotex.

That's interesting.....who is that?

 

[pargyle]

That's interesting.....who is that?

You probably know them ...

https://www.thermafleece.com/
I understand that they are looking at trying to make it more rigid ... I came across them when I was looking at various types of insulation for the house I hope to build eventually, It appeals to me that it is using (at least in part) British Wool and they are based in the UK - sheep farmers are having a really tough time with wool at present, it costs more to shear the sheep than the fleece is worth and if we started to use more of it as insulation in our homes it would gradually make it a viable commodity. Whether it is yet up to the equivalent R value of PIR ... not sure - but it's a product that is developing so ... I keep an eye on them.

 

[Newbeeneil]

After this weeks Countryfile about sheep and the fact they are composting fleeces because its cheaper to do that than get them to market. I compared the cost of wool insulation to Glassfibre. Even at rock bottom fleece prices the wool is about 6 times more expensive than glassfibre with a similar conductivity.

 

[jenkinsbrynmair]

The Welsh have much in common with New Zealanders....

I suppose so - we managed to get suckers to buy up all or derelict unwanted peasant hovels in Wales, and it was a Welshman in NZ who got suckers to pay through the nose for their unwanted manooky honey

 

[pargyle]

After this weeks Countryfile about sheep and the fact they are composting fleeces because its cheaper to do that than get them to market. I compared the cost of wool insulation to Glassfibre. Even at rock bottom fleece prices the wool is about 6 times more expensive than glassfibre with a similar conductivity.

Yes ..you are right ... although it compares favourably in price with PIR if you want the equivalent insulation value but there is something I'm not understanding about the insulation properties in terms of what each thickness of material achieves and the cost/value implications . The following are from the Roofing Superstore (I've bought from them in the past and they are usually about the best prices).

Cosywool Thermafleece 150mm 4.9 sq mtr £69.49 - 0.039 Wm-1K-1 £14.19/m2

Cosywool Thermafleece 50mm 14.8 sq mtr £70.16 - 0.039 Wm-1K-1 £4.74/m2

Isover loft roll fibreglass 150mm 9.3 sq mtr £22.79 - 0.044 W/mK. // 2.30 m²K/W. £2.45/m2

Recticel (PIR) 100mm 2.9 sq mtr £41.26 - 0.022 W/mK. // 4.50 m²K/W. £9.16/m2

So, I'm not sure ... I need to know a bit more about the thermal insulation properties of each type of material and I dnn't have that knowledge yet. I would like to be using an ecologically sound material for insulation but I don't have the pockets to pay significantly more than the 'market rate' for such materials ...

 

[enrico]

That's interesting.....who is that?

I have used sheep's wool for underfloor insulation. Beware, if it gets damp it stinks!

 

[Sayle]

Yes ..you are right ... although it compares favourably in price with PIR if you want the equivalent insulation value but there is something I'm not understanding about the insulation properties in terms of what each thickness of material achieves and the cost/value implications . The following are from the Roofing Superstore (I've bought from them in the past and they are usually about the best prices).

Cosywool Thermafleece 150mm 4.9 sq mtr £69.49 - 0.039 Wm-1K-1 £14.19/m2

Cosywool Thermafleece 50mm 14.8 sq mtr £70.16 - 0.039 Wm-1K-1 £4.74/m2

Isover loft roll fibreglass 150mm 9.3 sq mtr £22.79 - 0.044 W/mK. // 2.30 m²K/W. £2.45/m2

Recticel (PIR) 100mm 2.9 sq mtr £41.26 - 0.022 W/mK. // 4.50 m²K/W. £9.16/m2

So, I'm not sure ... I need to know a bit more about the thermal insulation properties of each type of material and I dnn't have that knowledge yet. I would like to be using an ecologically sound material for insulation but I don't have the pockets to pay significantly more than the 'market rate' for such materials ...

Cosywool Thermafleece (50mm) is in fact the insulator that I use for my hives!

 

[oliver90owner]

Not read the thread, but I had a sticker on the side of my Landy, for years, which said “wear wool - 35 million sheep can’t (all) be wrong.” ‘All’ in brackets as I can’t remember if it was included on the sticker.

 

[pargyle]

Cosywool Thermafleece (50mm) is in fact the insulator that I use for my hives!

I wondered if it might be ... there are not many manufactuers of wool based insulation about. I'm still not sure whether 50mm of Thermafleece on top of the crownboard is as thermally effective as 50mm of PIR. (Or indeed in most of my hives 100mm). Unfortunately, I don't feel inclined to lash out £70 on Thermafleece to do a side by side test ... most of my PIR come free from skip diving ! I'd like to know though ...

 

[Sayle]

I wondered if it might be ... there are not many manufactuers of wool based insulation about. I'm still not sure whether 50mm of Thermafleece on top of the crownboard is as thermally effective as 50mm of PIR. (Or indeed in most of my hives 100mm). Unfortunately, I don't feel inclined to lash out £70 on Thermafleece to do a side by side test ... most of my PIR come free from skip diving ! I'd like to know though ...

Well I can't give you any assurance one way or the other - I haven't done the tests beyond some heat-simulation sims in Energy2D. But in the top of my hive I scrap-fit an 'emergency' roof that ended up being deeper than needed because I had some excess ply in brood-box size, so I actually have...probably about 300-350mm worth of wool in the top. Obviously colossal overkill that will be substantially reduced when I get round to knocking together a proper feeder/roof box. Right now I'm working on insulating a second brood box.

The main advantage I've found with the wool is that I put an upturned container of fondant on top of the feedhole and just drape the wool over rather than having to purpose-cut a hole for it. Same with a rapid feeder.

 

[bingevader]

Unfortunately, I don't feel inclined to lash out £70 on Thermafleece to do a side by side test ... most of my PIR come free from skip diving ! I'd like to know though ...

Where are you getting those prices? Ty Mawr doing 14.8sqm for £60, that's less than £2 a hive! Shame you'd have to bulk buy!

 

[Sayle]

Doing some of those sims, you can really see the different insulation makes.



Here you can see both Thermafleece (wool) and Celotex (PIR) are both good insulators. They stop the heat moving out with any rapidity. Let's compare that with 20mm wood (about the thickness of your average hive wall, roof may vary)


Oof. You can see that the wood is letting a lot of heat through quite rapidly, with the space between the heat source and the barrier (the wood) fluctuating quite a bit. Compare that to the nice and uniformly toasty space under the PIR board. Now let's model the worse-case scenario: you have vents in your roof space providing direct access to the outside air and only the coverboard between your bees and that environment. Let's say it's a Thorne's 6mm birch ply cover.



Yikes. You're losing heat so fast that areas under the coverboard are going cold and you can actually see a plume of heated air escaping after being conducted through the plywood. Quick checks with the thermometer show that for every 30 degrees of heat your bees generate, you're losing 21 degrees of that. 70% of the energy your bees are using is being wasted. Compare this to 5 degrees for the 50mm of PIR board, where they are only losing 20%. That's quite a substantial difference. In a world of spherical cows, you could even argue that the insulated bees are going to eat a third of the stores compared to the uninsulated bees.

 

[Gilberdyke John]

⁶

whether it substantially matters: it doesn't).

So its all semantics then?

 

[Sayle]

⁶
So its all semantics then?

It could influence your choice of insulator. Having a well-rounded knowledge of the materials that you are using can be a good in itself - it doesn't need to be immediately applicable or important to have value. Being inquistive about these things is good - imagine if celotex was half as good if it was wet but nobody mentioned it because it's usually only used in wall spaces where it stays dry? Given the amount of misinformation and damn-near superstition in our little community, I'd much rather have too much information than not enough!