Posted By: MartianWill Paul Mitton finally come on here and give us his long promised explanation and some reliable data

I'd understand why he wouldn't, as forums enjoy shooting manufacturers' representatives to bits, detecting trade bias etc. Having one hand tied behind their back, such guys have retired wounded from this forum more than once, no doubt reprimanded by their MD. As I understand it, Paul Mitton and other CMM members have presented copious evidence to the testing community.

Posted By: MartianMy own view as one of the aforementioned BCO's and with a fairly solid scientific background, is that the EOTA process will indeed ignore the CMM's workshop results

Martian hopes! I still can't understand why an honest godfearing Building Inspector would nail his colours to the mast of a clearly creaky old ship, in such a partisan manner. Whereas my own partisanship is perfectly right and proper, of course! Anyway, the CMM's workshop results have been good enough so far, to force the current process, in which the entire insulation testing methodology is currently being rethought. Too late - the cat's already out of the bag.

He's cunning - waiting till I've forgotten I'm owed a return punch!

Martian, I greatly appreciate our to-ing and fro-ing, which has frequently driven me to re-think or think further, and it was you that provided me the scientific key to understanding the 'what do layers 2-6 do' question. I am sure there will be plenty 'more I (you) can say, really', as the story continues to unfold - good!

Hi Gary, I would not be happy with the advice you have been given by Thinsulex. Such a flippant response would steer me away from them towards another product. They may well be the only ones which carry certification, but that does not mean that you cannot use another product using the same methodology. I would try the technical department of a competitor and see what they have to say about the air gap. My understanding is that it is critical.

Regarding the other project, what you say is very inthttp://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1542&page=1#Item_2eresting. Not sure from what you say whether or not you live there but since it is snowing, it would be most interesting to go outside and look at each of the roof slopes. There is a further discussion just started here

Gary, the comments regarding air spaces are a direct contradicion of their own BBA.
Like all multifoils, no air space then basically not much thermal insulation. To be fair to date Thinsulex have been open on their product's thermal performance but like the other manufacturers more obtuse when relating to other performance characteristics like moisture pickup and fire.

http://www.customaudiodesigns.co.uk/thinsulex/BBA_cert.pdf

• thermal resistance of insulation (thickness 30 mm)
0.92 m2KW–1
• thermal resistance of the insulation including
air layers and bridging (see Figure 1) �
1.69 m2KW–1.

Posted By: MartianThinsulex .... can work fine together with PUR, PIR or fibre quilt insulants to achieve your aims

but only, you say, as well as "a single low emissivity layer".
Oh c'mon, even Thisulex's conservative "tested and approved .... recognised by building control" figures are way beyond what a single low emissivity layer would achieve. Strange that you acknowledge the effect of a single layer but deny the effect of stacking multiple layers together. Is this a relic of the old 'what do layers 2 to 6 do?' fallacy? (for which you you yourself kindly provided to me the theoretical means to lay the myth to rest, in this forum).

Posted By: fostertom

Posted By: MartianThinsulex .... can work fine together with PUR, PIR or fibre quilt insulants to achieve your aims

but only, you say, as well as "a single low emissivity layer".
Oh c'mon, even Thisulex's conservative "tested and approved .... recognised by building control" figures are way beyond what a single low emissivity layer would achieve. Strange that you acknowledge the effect of a single layer but deny the effect of stacking multiple layers together. Is this a relic of the old 'what do layers 2 to 6 do?' fallacy? (for which you you yourself kindly provided to me the theoretical means to lay the myth to rest, in this forum).

Hi Tom,
I think you misunderstand both my contribution above and what has gone on in the past.
Firstly I do not suggest a single low emissivity layer in addition to a multifoil. I am suggesting that it be used in conjunction with additional "traditional" insulation INSTEAD of a multifoil.
The main uses of a multifoil as I see it are to improve air tightness and to reduce radiated heat transfer which (materials wise) are more efficiently achieved by a single layer. When you consider the U-value per unit thickness of the material itself, multifoils are a very expensive option and you would be better with PUR.
Why should I not acknowledge the effect of a single layer and deny the effect of stacking multiple layers together? I have consistently done so and the National Physical Laboratory tests verify this conclusion.
The "fallacy" in your whole theory of multifoil insulation is caused by a misunderstanding. When you imagine how heat is being transferred between intermediate layers, you over-emphasise the relative effect of radiation over direct conduction. To be of any use a low emissivity layer MUST face a very low density, poor transmitter of heat. A gas such as still-air or better still Argon is pretty good, or going a step further, a vacuum is ideal. Where it is in direct contact with a wadding-type insulating layer, as it is on the intermediate parts of a multifoil, the aluminised surface simply acts to INCREASE the thermal transmittance to that wadding layer. The wadding may seem a good insulator to you, but compared to a gas it is very bad. The major part of the thermal resistance of a multifoil insulated element relies on the combination of the low emissivity surfaces with the air layers and not much to do with the shiny inner layers and wadding, as has been proven by the NPL.
Your claims to have provided some acknowledged theoretical explanation of an imagined phenomenon are bizarre and unfounded.

Ah sorry Martian, ambiguous words. I said

Posted By: fostertombut only, you say, as well as "a single low emissivity layer"

. By 'as well as', I meant 'as effectively as' - you understood 'in addition to'. Does that make any more sense of the rest of it?

Martian, do you really trust any of these software to give something like an accurate calculation of anything but the very simplest model?
from what I have seen of these types of software they are too limited in their abilities to be relied upon.

"Where it is in direct contact with a wadding-type insulating layer, as it is on the intermediate parts of a multifoil, the aluminised surface simply acts to INCREASE the thermal transmittance to that wadding layer"

Your post above was very incisive and seems to me to cut to the bone of the matter, not many people appear to understand the physics involved with this type of insulation. In an ideal world these layers of foil would be seperated by a vacuum and the foam is just there as an infill/sperator because they cannot seperate the low emissivity surfaces any other way. the question is to what extent the beneficial properties are compromised by the side effects of contact with the filler material. I agree that proberly the prime beneficial effect felt when this stuff is installed is that it reduces airloss.

Posted By: Terrymmm, just wondering if it is a good idea to use Cellotex software to model the arch enemy's product?

Yes ... which is why I suggested that someone could bung the figures into some independent thermal modelling software. I will try it myself in Superheat but am not sure if it is sufficiently sophisticated.

Posted By: MartianTherefore 32.5mm PUR outperforms 30mm Tri-iso even when you allow for the squashing of the tri-iso at the pinch points .... or can you see a failure in my logic?

i wouldn't doubt that at all, nor the NPL findings (nor the Thinsulex certification) - under steady state conditions, as artificially created in the hotbox test methodology. However under real-life dynamically varying conditions, it's a very different story.

Under steady state, on a micro scale within any insulation material, most of the heat transfer is by internal conduction and convection (internal radiation insignificant) and conventional insulations resist conduction and convection well; multifoils resist conduction and convection no better than you'd expect from a thin bit of wadding and some vague airspaces.

Under real-life dynamically varying conditions, couldn't be more different. I've previously explained my understanding of how on a micro scale within the insulation material, then nearly all the heat transfer is by internal radiation, and internal conduction and convection are insignificant. Conventional insulations are almost defenceless to resist radiant transfer; multifoils are designed to do just that (and to hell with the internal conduction and convection).

So under real-life dynamically varying conditions, conventional insulations do a lot worse than we've been mis-sold by BRE for 50yrs to believe (performance as low as 40% of expected), as is every building professional's common experience. And multifoils do 'unexpectedly' much better than any hotbox investigation will suggest.

Om Mar 5 in this thread I wrote:
"(without)..... the vital link between a) internal radiant transfer and b) fluctuating temperature .... his "excellent summary" (the NPL Report) will be so incomplete as to miss the point entirely. Though ignored by Martian, the fluctuating temperature issue is in fact prominent in the first sentence of the NPL Report abstract. But the NPL's "Temperature cycling" suggests such weedy fluctuations - one can imagine the carefully-stabilised hotbox temperatures being permitted to change slowly and steadily over a period of hours or minutes. A far cry from the sharp step changes that occur in real life - the sun comes out, a gust of cold wind, someone opens a window. all of which create a seething complex of non-steady-state temperature inequalities, advancing temperature wavefronts, possible anihillation and reinforcement of same where they intersect, all of which get evened out predominantly by internal micro-scale radiant transfer - readily in the case of conventional insulants, against great resistance in the case of multifoils."

The NPL Report is a classic case of Intentionality at work. which is fine because that's the way the universe works, though low-grade conventional science is still locked in obsolete denial of same, and so ends up studying not how the universe works, but how the old conventions of science work. The old boys at NPL I am sure 'knew' beforehand broadly what their study would show - that multifoils are a scam and that 50yrs of BRE methodology is a bright and new today as it ever was, hopefully, otherwise a lot of expertise-based jobs and lucrative consultancy work would cease overnight in a scandal of long-term scientific mis-advice.

The NLP scientists clearly, unconsciously, rigged the study to produce the results they 'intended'. They did this by accidentally forgetting to inform themselves of the typical pattern of dynamic variation that occurs in real life, which is vital to multifoil's functioning - in fact multifoils don't really work at all in other-than-dynamically-varying conditions.

So going back to Martian's "can you see a failure in my logic?" - the flaw is to rely on the NPL Report.

Posted By: Paul in Montreal

Posted By: fostertomin fact multifoils don't really work at all in other-than-dynamically-varying conditions.

So does that mean any multifoil insulation wouldn't have worked at all last night where the temperature was a steady 4C here in Montreal

I don't know Paul, but I doubt, even if the thermometer holds steady at 4oC, that that amounts to steady-state. First there's the diurnal lag to be equalised, and that never stops, but I suspect is too slow a 'dynamic' to bring the internal radiant component into full dominance. Overlaid on that is momentary wind-chill and evaporative/wetting chills, which can create quite a sharp short temp drop at the surface. Or was last night completely still? Then there's internal changes - opening doors allow bubbles of warm air to enter another room, hot water is used and evoporates, the cat sneezes ... or did not even a mouse stir overnight? Did you heating system maintain steady temp all night or does it decline to a setback temp till morning? I note the extreme measures that have to be taken to attain almost-impossible steady-state in the hotbox. I note the endless chaotic macro- and micro-turbulence that's being discovered, and realised as enormously significant, in all systems including the weather. Is you local bit of weather, and your house interior, any different?

In the slide-rule era, humans had no alternative but to look for broadly-averaged measurements, that could usefully approximate reality, but in so doing found 'inexplicable' (and therefore denied) anomalies that are now realised to arise out of the true chaotic patterns of systems - which chaos theory is now begining to understand, made possible by computers that can number-crunch huge datasets to uncover behaviour patterns previously undetectable and unpredicted by the simplified slide-rule theories characteristic of 19C and most of 20C (note that 'chaos' doesn't mean random, unpredictable, senseless, unscientific, unmanageable - it's entirely scientifically-accessible and manageable, just requires understanding abstracted to a higher, pattern level).

As I see it, multifoils 'happen' the more rapid the micro-scale local rate of change of temperature is. It's not the amplitude of the change - it's the instantaneous rate of change, which can include almost immediate reversal of the change.

Even for tiny local temp differentials arising across a void space within an insulant, almost all the re-balancing heat transfer that then happens, begins immediately by radiant transfer. And as radiation is instant, regardless of distance across or round the perimeter of the void, the radiant transfer is completed long before convection and radiation have time to make the distance. The lag-less radiation has plenty of time to equalise, infill and anihillate the temp differential, before the lagging convection and radiation has time to make the trip.

Only once a steady-state is established, does that lag lose its importance. Then, convective and conductive flow gets established because by definition the temp differential or gradient is steadily maintained and not anihillated by rapid radiation. Then radiant becomes only one mode amongst three, and typically in steady-state conditions is the smallest component. But as soon as a temp perturbation arises, radiant is instantly dominant again, becomes the only mode that's significant.

So any insulant that's designed to resist internal convective and conductive transfer will only be effective in steady-state conditions, which I believe barely exist in real life. An insulant that concentrates on resisting internal radiant transfer is what cuts the mustard in the real world - which is why Sheffield Insulations spent £6m on the technically most advanced producer of the insulation of 21C, and why the testing houses of Europe are currently spending millions on building new-style insulation test rigs that are designed to reproduce, record and number-crunch the data arising from dynamically-varying tests.

Martian, instead of resorting to blanket disparagement, pick on any one bit of it and say exactly how it disagrees with your understanding. You can e.g. propose a mind-experiment, as Paul just did, and as you did just before, to illuminate the point(s) where understanding diverges.

You really do your homework Paul - impressive. Two things you haven't covered - the diurnal lag (well, you can have that one), and more fundamentallyt "the endless chaotic macro- and micro-turbulence that's being discovered, and realised as enormously significant, in all systems including the weather. Is you local bit of weather, and your house interior, any different?" What does your version of the scientific mind think about that?

That's a nice question Tom

Is design data available for these test houses Paul?