Green Building Forum - Multifoil Insulation

Multifoil Insulation

Mike George — Thu, 02 May 2013 16:58:50 +0100

Yes, they've all moved on - though some are still happy to let folk believe what they will

Multifoil Insulation

fostertom — Wed, 29 Jul 2015 19:33:00 +0100

Posted By: Mike George
"The multifoilers tried to do that for decades and in the end they had to toe the line and accept the physics of the situation the same as everyone else"

No, they gave up against vested interest.

The new test rigs that would be capable of testing insulants in real-life dynamically varying (rapidly micro-fluctuating) instead of 'never in real life' artificial steady-state conditions, were cancelled near the last minute - because the conventional insulant manufacturers knew that their products would show up badly in those real-life conditions.

The multifoil guys readily agreed that multifoils give pathetic results under artificial steady-state test conditions - but excel the more dynamically varying the conditions. So let's not talk about

Posted By: Mike George
"accept the physics of the situation the same as everyone else"

The NPL study that was supposed to settle the matter was a shameless piece of 'who's the paymaster' science. They ignored the Multifoil manufs' hypothesis that they were supposed to be testing - heat transmission under dynamically varying conditions - and just repeated the familiar steady-state regime, using the familiar steady-state test rigs. Unsurprisingly, they got the results they were paid to, and the headline 'confirmation' results were accepted unexamined. As a sop to the multifoil manufs, they did run a test wth slowly-slowly varying conditions - as fast as the steady-state rig would allow - and concluded it made no significant difference - as the multifoil manufs would have confirmed.

Multifoil Insulation

fostertom — Wed, 29 Jul 2015 19:35:23 +0100

Posted By: djhThe actual report is freely available at the address below, if anybody wants to make their own mind up about its quality:

http://www.npl.co.uk/publications/evaluation-of-the-thermal-performance-of-insulation-systems-used-in-roof-structures.

Multifoil Insulation

fostertom — Wed, 29 Jul 2015 19:36:07 +0100

Thanks Dave, I'd lost track of it FWIW.

the precis at least confirms what I said - all done in a steady-state hotbox and lo and behold confirms expectations as well as FEA-type calcs (which were presumably run until equilibriation). So far completely ignoring the (real-world) conditions under which Multifoils are claimed to work.

Then they did 'temperature cycling' runs and the point is, as far as i remember, the period of those cycles was way way slower than the (real-world) quite rapidlly/dynamically fluctuating conditions under which Multifoils are claimed to work.

That's the kind of simplification that scientists like to make, in order to get the repeatable results that are the hallmark of Scientific Method. They may know it's just an initial simplification, but then they forget to come back and re-complexify the model, because it all looks so beautifully convincing. Then the simplified model is called 'scientific' and the real-life phenomena reported are just 'anecdotal'.

Anyone still think that real-world is steady-state? Just watch a WUFI 'movie' which runs a fascinating multi-parameter graph, as fast or as slow as you like, of what's happening heat-and moisture-wise at any given point in the wall 'sandwich', through the course of a year's weather file. No nice progressive diurnal/seasonal curves - they peak and trough like crazy, even with WUFI's coarse timesteps (is it 1hr or 15mins? I forget). In real life there are no timesteps, everything fluctuates continuously, non-linearly, both from gross effects like gusts of wind or sun coming out, and right down to inexplicable quantum variations I should think. It's the 'weather' within a multi-layered medium - bit like earth's biosphere! - and why shouldn't it display the same chaos-theory behaviour?

That range of real-life dynamic fluctuation creates fast-changing/reversing local temperature gradients, however tiny, which are mainly evened-out by instant-action radiant heat transfer within the tiny voids of non-metal materials (and maybe even between metals' molecules) long before slow-acting conduction/convection lumbers into action. So any insulant that's designed to resist radiation above all, can be very effective in blocking those real-life micro-fluctuations, which aggregate into the nett heat transfer that a hot-box can detect. Whereas your typical insulant has little resistance to radiant transfer, in fact its porous surfaces are ideal emitters.

When and if everything settles to a steady-state, however artificially contrived like in a hot-box, then the instant-action of radiant transfer ceases to be important; the 'heavy-lifting' of constant one-way heat is then done by conductive/convective transfer; which conventional insulants are good at resisting.

Therefore a steady-state hot box test greatly favours conventional insulants, awarding insulative performance which is not fulfilled in real-life fluctuating conditions. And of course multifoils bomb completely in steady-state hotbox tests.

Multifoil Insulation

fostertom — Wed, 29 Jul 2015 19:37:34 +0100

Posted By: Mike GeorgeI do have my reservations about the way in which NPL conducted their tests. But my reasons are not the same as yours Tom. Nothing to do with the radiation issue (which is what I was alluding to in my comment above).I'm sure we've discussed all this before on the other thread.........

I was also engaged by Paul Mitton (post CMM) to carry out some dynamic simulations using Tas and offer the results in a confidential report, which I did; and which I subsequently sent to the Lead Author of the NPL Report. They did not reply.... either to address my comments or to refute what I was saying...

Multifoil Insulation

fostertom — Wed, 29 Jul 2015 19:41:05 +0100

What do you think of that model of how radiation dominates in dynamically varying conditions? Don't say 'it's not been scientifically tested' (or has it?) - what do you think - could it even make sense?

Multifoil Insulation

Ed Davies — Wed, 29 Jul 2015 21:13:58 +0100

Tom, you're individual assertions seem to mostly make sense and be plausible but I don't see how they add up to reduced bulk heat transfer in multifoils in dynamic situations which doesn't apply in steady-state conditions. I think you are assuming something without making it explicit. Perhaps you could go through an example with particular temperatures for different parts of the material to show what you think is going on.

Multifoil Insulation

Mike George — Thu, 30 Jul 2015 01:15:49 +0100

Posted By: fostertomWhat do you think of that model of how radiation dominates in dynamically varying conditions? Don't say 'it's not been scientifically tested' (or has it?) - what do you think - could it even make sense?

Not to me no Tom. I did consider it for a very long time but the Physics is well understood (though not necessarily by me) Can so many great minds be wrong? I don't think so. For me the whole testing rig results about mineral wool v multifoil is about air losses - and the NPL hotbox does not reflect reality to me - A few odd holes in the test rig here and there if I remember correctly. So I modeled the different scenarios using Tas - with results favorable for multifoil.

I did also model different scenarios assuming the same air losses for both multifoil and mineral wool in order to isolate this from losses through conduction and radiation - the results pretty much reflected the text book theory.

Multifoil Insulation

Ed Davies — Thu, 30 Jul 2015 07:26:04 +0100

Tom, further question(s): which of the following do you think is true?

1) Multifoil performs better in â€œreal-worldâ€ dynamic conditions than it does in steady-state conditions.

2) Traditional insulations perform worse in dynamic conditions than they do in steady-state conditions.

One, other, both or neither?

Edit to add, actually, I now see that on the first page of this thread (in 2007) you wrote:

Posted By: fostertomas conventional insulations perform as expected in steady-state conditions but only a fraction as well under dynamically-varying temperatures; while multifoils do the opposite; this spec covers all eventualities, until we understand multifoils better.

That would be â€œbothâ€ then. Do you still think that?

Multifoil Insulation

fostertom — Thu, 30 Jul 2015 11:34:22 +0100

Yes "both" - but I don't know by what 'fraction'.

Also, multifoil is a very crude application of the resist-radiant principle I'm talking about. The ideal resist-radiant insulant would be a fine aero-bubble or other granular-void slab having a high void to solid ratio, and all the voids' internal surfaces chrome plated!
That way, there would be great resistance to the instant-action radiant heat transfer across the void spaces,
leaving nearly all the heat transfer to be done by conduction via the circituous solid path between the bubbles,
and by convection across the voids.
As the latter two modes are subject to lag due to the thermal capacity of the solid, and the thermal capacity and the inertia of the air, their delivery of transfered heat is much delayed compared to the instant-action radiant heat transfer.

Whether multifoil really exploits this mechanism, I don't know - but its proponents were (are) onto something, and if we by now had the suppressed dynamic-fluctuation test rigs, new understanding and new forms of insulation would be emerging.

Multifoil Insulation

djh — Thu, 30 Jul 2015 11:44:45 +0100

Posted By: fostertomWhat do you think of that model of how radiation dominates in dynamically varying conditions? Don't say 'it's not been scientifically tested' (or has it?) - what do you think - could it even make sense?

Multifoil insulation is mostly used by scientists in situations where radiation dominates, because that is where it is very useful. It gets used in insulating spacecraft and in cryogenic vacuum insulation. So I believe scientists understand very well how it behaves as regards radiation-transmitted losses as compared with conductive and convective losses. If they didn't, all kinds of experiments would be giving odd results, and spacecraft would be freezing or melting!

It's no good just saying 'scientists have got it wrong'. The way to say that to a scientist is to do an experiment that shows there is something wrong with current knowledge. And the experiment needs to meet the reproducibility test - some other scientist needs to be able to repeat exactly what you do and get the same result. When that has happened, the phenomenon will be taken seriously.

Multifoil Insulation

fostertom — Thu, 30 Jul 2015 12:01:18 +0100

Posted By: djhIt's no good just saying 'scientists have got it wrong'. The way to say that to a scientist is to do an experiment that shows there is something wrong with current knowledge. And the experiment needs to meet the reproducibility test - some other scientist needs to be able to repeat exactly what you do and get the same result. When that has happened, the phenomenon will be taken seriously.

Cmon Dave that's just a way to only allow proper scientists to have an opinion.

Of course MF originated in outer space where there's only radiation - we all know that. What have you to say about its use in air?

Multifoil Insulation

djh — Thu, 30 Jul 2015 12:09:20 +0100

Posted By: fostertomCmon Dave that's just a way to only allow proper scientists to have an opinion.

No, that's the way that science works. It's not like the Internet where nobody knows you're a dog or some therapy session where everybody's opinion is valued equally. Experimental results are what count.

Multifoil Insulation

SteamyTea — Thu, 30 Jul 2015 13:29:09 +0100

Posted By: djheverybody's opinion is valued equally

It may seem like that, but I don't think it is really.

Multifoil Insulation

djh — Thu, 30 Jul 2015 13:30:47 +0100

Here's an ongoing illustration of how science works when it comes across something unexpected ...

http://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-mission

Multifoil Insulation

fostertom — Thu, 30 Jul 2015 14:16:29 +0100

Yeah yeah but it still diqualifies everyone else, who hasn't got a research lab at their disposal, from making 'unproven' speculations, suggestions, common sense criticisms, inspired hunches, unblinkered/innocent fresh view etc.

Multifoil Insulation

djh — Thu, 30 Jul 2015 14:36:20 +0100

Posted By: fostertomYeah yeah but it still diqualifies everyone else, who hasn't got a research lab at their disposal, from making 'unproven' speculations, suggestions, common sense criticisms, inspired hunches, unblinkered/innocent fresh view etc.

Not at all, it just means that the likes of you and me would have to put a lot of effort in to get some off the wall idea accepted. Another approach would be to persuade your local politicians to spend taxpayers money doing the research. The point is that science works by experiments so you do need the facilities to do experiments, and somebody has to pay for those, so there has to be some method to choose what that money gets spent on. You could start a kickstarter campaign if you think you have a viable experiment that would demonstrate something new.

Anybody can make whatever speculations they like, but there's no particular reason why anybody should listen to them.

Multifoil Insulation

ringi — Thu, 30 Jul 2015 15:23:03 +0100

If current level of insulation are used, are we not getting close to a study state anyway once we get past the surface of the insulation?

However Multifoil insulation installed well with all joints tapes is clearly better the PIR with lot of gaps! But if one screw is put in the wrong place and makes a hole in the Multifoil.....

Hence something like LowE may be a better option if you don't want to use PIR.

Multifoil Insulation

CWatters — Thu, 30 Jul 2015 15:33:07 +0100

Just for info.. There has been a determination by the Secretary of State on the multifoil matter..

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/2818/Building_regulations_determination_CI-45-1-238.pdf

Multifoil Insulation

SteamyTea — Thu, 30 Jul 2015 15:46:42 +0100

Posted By: fostertomwho hasn't got a research lab at their disposal

I don't have a lab to work in any more, I can still do valid science though.
There is nothing to stop you writing up what you think is happening, as long as you can justify your assumptions. If you can think up an experiment to test it, that would be even better. I am sure it could be asted on and would probably take less time than this thread has been running.

Multifoil Insulation

Ed Davies — Fri, 31 Jul 2015 10:14:24 +0100

Posted By: SteamyTeaThere is nothing to stop you writing up what you think is happening, as long as you can justify your assumptions.

Exactly. It needs a much clearer explanation than just a bit of hand waving. At the moment I have no idea whether what Tom says has any validity and can't make useful comments without understanding it in more detail. Lab results would be great but a more precise explanation would go a long way.

E.g., Tom mentions non-linearity (and chaos). Where does that come from? All the processes involved are pretty much linear - even radiative heat transfer is pretty close to so at the small temperature differences involved. Why is radiant heat transfer considered â€œinstant actionâ€? OK, photons move pretty quickly but still it takes time for heat to move from one object to another with a similar order of magnitude rate as conduction.

Multifoil Insulation

fostertom — Fri, 31 Jul 2015 10:52:34 +0100

Well there's no way I'll be doing garden-shed experiments - tho I still think I'm that kinda guy, those days are past - I even have a visiting mechanic to put a bigger block in my Cabrio. My rusting tool kit stopped around 1988 Black and Decker time. So it's mind-experiments (inspired/informed hunches) or nothing. Doesn't mean I can't respond to challenge and provide more detail/better explanation.

To Be Continued

Multifoil Insulation

Ian1961 — Fri, 31 Jul 2015 13:56:42 +0100

I'm a new member to the forum which I've been reading with great interest recently. This is my first post and I've hesitated about contributing on this particular thread as it looks very contentious, nevertheless I thought I'd contribute my experience of multifoil insulation for what it's worth.

I'm an architect based in the UK and about 10 years ago I was employed on a large Â£5M project in connection with the renovation and extension of a very large 3 storey grade 2 listed house. Due mainly to planning constraints with the listed building we used a Triso multifoil as the only insulation in the walls and roof of the older parts of the property. The building had a new heating system which was sized to take into account the manufacturers claims for the Triso insulation - everything worked as we hoped it would.

It was the first time that I had specified a multifoil insulation so we discussed it at length with the (very demanding) client beforehand. The BCO was also okay with the product.

Multifoil Insulation

fostertom — Fri, 31 Jul 2015 14:13:57 +0100

And how did it work out? Triso was used alone, or with their later spec coupling it with insulation board? Was it Triso 9 or 10? Is that the type that's peppered with holes and/or stitching holes, or is it imperforate - in latter case did you tape joints or try to make it airtight? Did you install it in cross-battening for minimum compression (e.g. just 50x50 squares compressed at 400c/cs in both directions) and for minimum contact (facing into clear airspace) to both faces?

Multifoil Insulation

Ian1961 — Fri, 31 Jul 2015 14:29:59 +0100

"And how did it work out?"

It worked as the manufacturers claims - the building's new heating system was sized with the Triso in mind and it performed as planned. (The original building had uninsulated solid brick walls and an uninsulated slate roof on exposed timbers)

Spec - it was ten years ago and I'm just going off memory but I'm sure we used Triso Super 9 which I understand has since been superceded by their current version 10. Workmanship on site was excellent with a really good main contractor and the client (who was an engineer by training) was full-time on site as well. The Triso was installed exactly as manufacturers recommendations so minimum contact with a clear air space each side. A lot of attention was paid to airtightness - taping etc.

To give you an idea of scale of the project the main contractor who was a specialist in listed building work was on site for 2 years with about 30 tradesmen - it was a big job.

Multifoil Insulation

Mike George — Fri, 31 Jul 2015 14:33:53 +0100

Hi Ian, very interesting. I wasn't aware that they had Certification for Tri -iso for solid walls back then. Can you recall what Certification the manufacturers specification carried?

Multifoil Insulation

Mike George — Fri, 31 Jul 2015 14:40:09 +0100

Hi Ian, very interesting. I wasn't aware that they had Certification for Tri -iso for solid walls back then. The only one I can find now is for walls in loft conversions - though I haven't looked extensively...Can you recall what Certification the manufacturers specification carried?

Multifoil Insulation

Ian1961 — Fri, 31 Jul 2015 15:15:51 +0100

Mike,

Sorry, it's over 10 years ago and I can't remember what certification the Triso Super 9 had back then at the time we were at the specification stage of the project. With the building being listed we didn't really have many practical alternatives to multifoil.

Normally, for PI Insurance issues, I wouldn't specify products that didn't have at least a BBA certificate but sometimes you have to use your own judgement and in this case we discussed the product at length with the client (who had better technical expertise as an engineer than me) before coming to a decision.

BCO - we used an approved building inspector rather than the local authority. This is one of those instances where the BCO was able to use his own judgement in deciding whether the product satisfied the regs or not.

Multifoil Insulation

SteamyTea — Fri, 31 Jul 2015 15:22:27 +0100

Posted By: fostertomSo it's mind-experiments (inspired/informed hunches) or nothing

Nothing wrong with that, as long as you use decent references to back thing up.

A bit about Trisco 9 here.
maybe our old mate Timber can shed more light on it (if he is still about)

http://arquitecologia.org/multi-foil-insulation.pdf

Seems that

Posted By: Ian1961It worked as the manufacturers claims

is a little bit open to interpretation.

Multifoil Insulation

fostertom — Fri, 31 Jul 2015 15:25:19 +0100

Was it peppered with holes and/or stitching holes, or was it imperforate?
In use, any feedback from occupants?