Phase change insulation: what to think of this?

[Garald]

[No, I won't use it myself, since I just got chided with "there's the lab and then there's practice" by my architect for mentioning Aerogel panels. I'm still trying to make her reconsider Aerogel plaster...]

 

A friend was telling me about phase change insulation. Apparently this has been discussed for years, but fire safety is or was a problem - and now there's a product in the market with a fire safety rating.

 

https://www.savepurenergy.com/?fbclid=IwAR0f2yozWkhglUGBYY1YjUvjWF8eI_gHRDkKPVS_8en844GMFiCbCTdXSKc

 

Just out of curiosity, what do people think of this?

[ProDave]

Their little infographic talks of a temperature range from 118F to 78F   That's 48C to 25C

 

In a typical UK house with indoor temperature 20C and outside temperature much less than 20C, I fail to see the relevance of this 48 to 25C band they are talking about?

 

I could see it stopping, or substantially slow a house from heating inside in a very hot climate?  Is that it's aim?

 

Oh and it looks remarkably thin and like a multi layer foil type product and I don't think a lot about them.  If it really is a pcm then surely even that would need some mass of material to store the heat in, not an ultra thin sandwich of materials?

[saveasteading]

I believe it is still available in some ceiling panels, in little capsules or grains. The size doesn't matter and doesn't change significantly.

It is a solid changing to a liquid by absorbing energy in daytime then returning it to the space by turning solid again.

Rather like ice changing to water and water to steam, but using resins, large amounts of energy can be stored in small volumes.

More realistically it will be useful as large stores of heat....I think I saw it proposed as 100mm dia tubes of resin  stored under house floors.

5 years ago it was coming soon....

 

I am not commenting on the product mentioned....more study required to get up to date.

 

[Temp]

11 hours ago, Garald said:

I'm still trying to make her reconsider Aerogel plaster

As I recall real Aerogel is only about twice as good as PIR foam.  Real Aerogel is also fragile so i don't think the form used in insulation is the same. 

Have you got figures for the thermal resistance to compare?

 

As for phase change materials...They are being used in thermal stores. They will add thermal mass to a building but how much? I suppose they might smooth out temperature variations so that daytime and night time temperatures get averaged. I'd be surprised if they added enough heat capacity to act as  a practical interseasonal thermal store. 

 

[Garald]

1 hour ago, Temp said:

As I recall real Aerogel is only about twice as good as PIR foam. 

I know. We won't be able to bring that piece of walls up to norms now; we are in harm-minimization mode.

Edited December 14, 2022 by Garald

[SteamyTea]

These phase change materials have been around for decades.

They are usually a coated wax sphere embedded in a sheet material.

If they were any good, we would all have them.

4 hours ago, Temp said:

. They will add thermal mass to a building but how much

None at all, thermal mass is a nonsense term. It assumes that the mass is the important part, not the heat capacity and the thermal conductivity.

 

 

Paraffin Wax has a latent heat of fusion of 190 kJ/kg and a density of 900kg/m³.

Plasterboard has a SHC of about 0.84 kJ/kg.K and a density of 1000kg/m³.

So on the face of it, for the same mass, phase changing wax seems useful.

But that is comparing phase change with non phase change.

Paraffin wax usually has a SHC of around 2 kJ/kg.K. so a little over twice as 'good' as plasterboard.

So adding thicker plasterboard would have, except in the small thermal window of phase change, the same effect.

And that is if the whole area was covered in phase change material. If the miracle board had less than 45‰ wax in it, it would have very similar storage capacity and response times.

 

So my verdict, not worth the bother.

 

Thermal conductivity is of little relevance as any sheet material should be backed up with good insulation on the cold side.

Edited December 14, 2022 by SteamyTea

[Temp]

When I say Thermal mass I mean Heat Capacity 🙂

[Radian]

12 hours ago, Temp said:

As I recall real Aerogel is only about twice as good as PIR foam.  Real Aerogel is also fragile so i don't think the form used in insulation is the same. 

Have you got figures for the thermal resistance to compare?

 

You can have a play with Fixit 222 on ubakus

 

Edited December 14, 2022 by Radian

[Radian]

[Radian]

[Garald]

But when it's -5 C outside, I do get condensation:

 

What to do?

[Garald]

(Of course, the average temperature in Paris during winter months is around 3C, not -5C. Does this mean I should not worry?)

[Radian]

You definitely need to understand the materials involve in the construction of the external wall. By insulating the surface on the inside, you move the dewpoint out into the wall. Whether or not this is an issue for the wall needs to be understood. The problem is you may do too good a job of insulating the inside. If you downgrade the insulation by swapping the plaster for thin sheets of composite XPS (Ubakus suggests WLG 035) then the dewpoint remains below saturation point throughout the structure and still prevents condensation on the inside. To see this suggestion, disable the plaster layer and look at the Moisture report with 20^oC/50% in, -5^oC/80% out:

 

Mould protection

The temperature of the inside surface is 13,1 °C leading to a relative humidity on the surface of 78 %.Some kinds of mould start to grow at relative air humidities of 70% or more, mould cannot be excluded!.

Under the given circumstances, mold formation can be avoided by the following measures:

• Reduction of the relative humidity of the room air to 45%
• Increasing the surface temperature to 14,7°C by (additional) thermal insulation. This would require about 10 mm insulation (WLG 035).

[Garald]

Grzegorz the Contractor just poked into the wall panel. It's an empty space of 4 to 5cm! Beyond that, there is the external wall, which may actually be single-width masonry, not double-width - the architect hasn't confirmed.

 

Now the question is how to fill those 4 to 5cm. They are probably full of old rock wool at the level of the attic, but by the staircase they really are empty.

[Radian]

https://insulationgo.co.uk/53mm-british-gypsum-thermaline-pir-mr-insulated-plasterboard/ PUR backed gypsum composite?

[Garald]

 

On 21/12/2022 at 20:25, Radian said:

https://insulationgo.co.uk/53mm-british-gypsum-thermaline-pir-mr-insulated-plasterboard/ PUR backed gypsum composite?

 

We decided against PIR some time ago, as we couldn't get solid assurances about (a) toxic fumes when not on fire (b) toxic fumes when on fire. I think PUR would be roughly the same (though gypsum composite means it would be less likely to catch fire, presumably).

[Radian]

15 minutes ago, Garald said:

I think PUR would be roughly the same (though gypsum composite means it would be less likely to catch fire, presumably).

If it ignited behind the gypsum you should have long since evacuated the building. However it's your call on the environmental issues and toxicology.

[saveasteading]

Pur burns very rapidly, and also melts and flows. Pir burns but crumbles.

In a domestic situation it shouldn't burn, as what will ignite it and where would the oxygen come from?

Toxic fumes when not on fire? Don't know, but surely it would be on the far side of plasterboard and polythene.

 

[ADLIan]

PUR and PIR are very similar chemically, slight tweak in the formulation. They do not melt and flow in a fire (as polystyrene does), they are both combustible but pir will perform slightly better than pur. I’m not aware of any safety/toxicity issues from either product as supplied as boards - the manufacturers would have to make you aware in their health and safety data. Products of combustion are a different matter!!

[saveasteading]

I'm happy to learn that I'm wrong if I am. Perhaps pur has changed since last I checked, but we had clients' insurance companies checking that we didn't use it in composite panels.

So now from a quick check I find this from Kingspan.

 

The most notable differentiating factor for PIR is its flame and smoke resistance. PIR slows the spread of flames and reduces the smoke emitted from the fire when compared to PUR products.

[ADLIan]

Kingspan - see grenfell tower inquiry evidence. Both product variations are combustible. Depending upon formulation pir may achieve slightly better Euroclass rating,  D rather than E?

[Garald]

Right, as my architect says, PIR is a bit better than PUR. (This is a pun in French - "pire" means "worse". In fact, it also means "worst". Kind of makes you wonder what the PIR marketing folk were thinking")

 

Still, both products would be  at least slightly anxiety-inducing in a tiny corner staircase that is the only way to leave an attic where people work and sleep. (I suppose you can still jump from a second floor, but I definitely wouldn't recommend it under usual circumstances - knew somebody who did that while drunk - broke his jaw into three chunks. Actually, he fell from a first-floor balcony to a basement-flat landing while attempting to jump from one balcony to another, but you get the idea. Of course, if had been in a fire, that would have been a different story.)

Edited December 23, 2022 by Garald

[saveasteading]

It seems  from a very quick catchup  that Grenfell had pir on the wall, and polyethylene filled outer cladding. Not pur.

I have tested pir on a fire, and it burns rapidly, creating more heat and flame spread. Have never used pur or pet, assuming that is the term.

Long before Grenfell I met some firemen at a seminar. They told me that they kept well away from any composite cladding, especially secret fix, as it might suddenly fall off the wall.