Products: Multifoil Insulation

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- CommentAuthorMike George
- CommentTimeJun 1st 2010
Posted By: biffvernon
Posted By: Mike GeorgeSo are you saying that the multifoil in the BBA will achieve 1.9m2K/W irrespective of whether the air-gap is 20mm or a 'few nanometer'?
Paul answered that very well.

Doubtless the 20mm of air adds a lot of insulation. And the air costs nothing other than the space it occupies. The bit you are paying over the odds for, the foil, doesn't care whether there is an air gap there or not. It's performance will not be affected by the air gap. It's a shame that the BBA and the BRE do not make clear the operation of pretty basic physics.

The purveyors of thermal vests don't say this garment may only be worn in conjunction with a shirt and woolly jumper if you want to stay warm on a cold day.

No they don't.

But I think that it is clear enough in the BBA that they are saying the 20mm air gap is required to get the declared performance, and doing so on the basis of tested results. The bit thats not clear is whether the tests were conducted in a hot box. As you know this was the biggest criticism levelled at the in-situ test results previously attained by Actis et al so I think it unlikely that the BBA would go down the same route without testing compliant with BR443 or equivelant European standard. But... its not clear how the testing was carried out
- CommentAuthorfostertom
- CommentTimeJun 1st 2010
BR433's applicability to multifoils was established only by commercially-motivated sleight of hand, by bureacratic dictat without any scientific ratification. BR433 was extended, with some (but IMHO misguided) scientific input, to cover foil-faced bubblewrap. At a later date, by no-one's leave, that was deemed to cover multifoils.

As it happened, within the timetable of the defensive manoevres conducted by the conventional insulation industry, that one action effectively put back CMM's (Confed of Multifoil Manufs) progress towards getting their evidence properly considered by the European testing establishment, by 1.5yrs. The High Court eventually ruled that deeming unscientific or unlawful or something, and the Multifoil manufs looked forward to sueing for loss of earnings. Not sure if they did that, but the present situation is that the Multifoil manufs have accepted defeat, for now.

It's a long and sordid tale, and I can't understand how so many on this forum don't see it for what it is, don't bother to understand what CMM was saying, based on extensive (highly modifed hotbox) testing, and seem determined to continue believing the obsolete, simplistic pseudo-science of the conventional hotbox. Especially as those same people are so ready to embrace aerogels and graphited insulants, whose behaviour is equally inexplicable in conventional terms.
- CommentAuthorPaul in Montreal
- CommentTimeJun 1st 2010
Posted By: fostertomembrace aerogels and graphited insulants, whose behaviour is equally inexplicable in conventional terms.
It's not inexplicable at all - see my earlier reply.

Foil-faced insulation has been tested over here in real buildings and its performance is in line with what you'd expect for double glazing that has low-e coatings. Once you start to add in all the required airgaps then you're back to the same thickness as conventional insulation and you'd get about the same performance for the overall assembly thickness. Where it is more effective is in climates that have extreme cooling loads due to strong sunlight on roofs. I even have a foil sunblocker for my car which works well when I'm parking in sunlight. But for dark spaces inside walls that are subject to normal air temperatures, the foil faces add very little difference to the overall performance, which, despite your protestations to the contrary, are not dominated by radiation, no matter how fast the external temperatures are changing. For what it's worth, the initial momentum transfers in conduction and convection are carried out at the speed of light via the electric field so there really is no difference.

Paul in Montreal.
- CommentAuthorfostertom
- CommentTimeJun 1st 2010
Posted By: Paul in Montrealthe initial momentum transfers in conduction and convection are carried out at the speed of light
Maybe but the effect of conduction and radiation is far from at the speed of light. The effect of radiation is indeed at the speed of light.

I do hope you'll directly crit what I said above, in response to your 'Hope this helps clarify your misconceptions'.
- CommentAuthorMike George
- CommentTimeJun 1st 2010
Tom, I don't think the Hot plate/box is the be all and end all either, but given that it is the hoop everyone has to jump through its not surprising that the multifoil boys have taken the 'if you can't beat them join them' attitude to compliance.

My view is that the original in-situ tests carried out by Actis et al showed multifoil in such a good light largely because of the superior air tightness of multifoil over mineral wool. I have an open mind as to how much radiative heat transfer contributed to the results but confess to not being able to follow some of the claims and counter claims made here.

Curiously though, there seem to be very few peer rieviewed publications looking specifically at heat loss through multifoil. If all of this were so easilly explained then why is that?
- CommentAuthorbiffvernon
- CommentTimeJun 2nd 2010 edited
Posted By: Mike George
But I think that it is clear enough in the BBA that they are saying the 20mm air gap is required to get the declared performance, and doing so on the basis of tested results.

The trouble is that the BBA did not make clear that the air gap was to add an additional dose of insulation to that provided by the mutifoil, rather than allowing the foil to do it's radiation stopping work in some pseudo-science role. This has lead some folk to think foil has to have an air gap for foil to reduce radiation. This is wrong. Like I've said a few times, foil only needs a one infra-red wavelength gap to do it's stuff.
- CommentAuthorMike George
- CommentTimeJun 2nd 2010
As far as I'm concerned none of that is clear from the BBA so we'll have to agree to disagree for a change.
- CommentAuthorSaint
- CommentTimeJun 2nd 2010 edited
Wrong quote.....deleted again...
- CommentAuthorSaint
- CommentTimeJun 3rd 2010
Especially as those same people are so ready to embrace aerogels and graphited insulants, whose behaviour is equally inexplicable in conventional terms.

Tom, "inexpicable"?
Aerogel is not only proven thermally in the globally accepted hot box test but also empirically in situ in aerospace, automotive, military, cryogenic, passive fire protection, IR suppression, oil and gas and a whole myriad of other industrial applications where failure can be catastrophic. Whereas multifoils have pitched their sales into a solitary and lets face it comparatively crude application, roofing insulation.
Based on the results of a ridiculously naive and cheap test carried out by a manufacturer who was singularly ignorant of the installation techniques of the very competitive materials they were intending to malign they succeeded only in damaging their own credibilty.
As for graphited insulants they do at least give a cursory nod towards the acceptance of the effect of radiation in ambient conditions but in doing so highlight the relatively minor scope of its influence at these temperatures
- CommentAuthordjh
- CommentTimeJun 3rd 2010
"Donâ€™t ask for my sources â€“ this is all out of my head. Itâ€™s like â€“ I donâ€™t need a peer reviewed research project to tell me that if A is faster than B, then A gets there sooner."

Indeed so and I don't have a problem with A is faster than B. I do question whether it is "significant", which is why I highlighted that word!

To show it's significant, as Mackay would tell us, the numbers have got to add up. Which means you need to show us some existing data that you believe is wrong and either some experimental evidence that contradicts it or else a testable theory and a prediction of what the true value should be. But you've consistently been unable to do that, despite repeated requests. And I believe you won't be able to present any such evidence, because there isn't any, because I think you've misunderstood the science.

As far as I understand what you're saying, you think radiation travels faster than conduction or convection. I think we can all agree about that. Then I guess you think that science has ignored this and so faster heat transfer will result in faster temperature changes when conditions change.

But that's not the case, because the speed of heat transmission isn't the rate-limiting step. The energy balance is what limits the speed of changes. Heat flows at some rate (watts) and that flow has to be collected over some time to raise the temperature of the material it is flowing through (i.e. it is integrated at a rate dependent on the specific heat of the material). It's that integration that sets the rate of change of temperature.

The conventional theory of heat transmission ignores the speed of transmission â€“ it assumes it is infinitely fast! Compare it with electrical circuit theory. The behaviour and frequency characteristics of circuits depend on the resistances and capacitances in them, not on the speed of the electrons or even the speed of wavefronts in the electric field.

Sure, if you increase the frequency to radio frequencies and beyond then you do need to consider transmission speed and you get waveguide theory etc. But if you applied that to the thermal case, it would actually slow down changes (i.e. improve the perfomance of insulation). It doesn't occur in the real world, though, because thermal envelopes have solid, relatively high-density, opaque materials on the outside and inside surfaces. Those layers of material act as low-pass filters so there's no very high-frequency variation transmitted through the body of the wall/roof/floor.

So I'm sorry but I think the speed of transmission is an angels on a pinhead type of question.

Nothing to see here, move along now please ...
- CommentAuthorfostertom
- CommentTimeJun 3rd 2010
Very good djh - this is response that I can get my teeth into - will be back soon - consulting my boffin as soon as I can catch him, incl about the terminology in the papers you posted.
- CommentAuthorfostertom
- CommentTimeJun 3rd 2010
Posted By: SaintAerogel is not only proven thermally in the globally accepted hot box test but also empirically in situ in aerospace ... etc
I'm not disputing that aerogel works - just that it's performance is theoretically inexplicable, tho Paul says it isn't, so I'll go back and read what he wrote 'previously' (a link wd be gd practice).

Posted By: Saintthe relatively minor scope of its influence at these temperatures
Platinum EPS's 0.31 is an extremely significant hike over ordinary EPS's 0.38 - puts XPS out of the running - hooray!
- CommentAuthorPaul in Montreal
- CommentTimeJun 3rd 2010 edited
Tom: here's how aerogel works - it talks specifically about IR absorption

http://www.aerogel.com/features/pdf/atp_4.pdf

See also http://www.scribd.com/doc/18440942/phD-Thesis-AerogelsMMoner-

and http://www.springerlink.com/content/v4126v5r152x622n/ where the abstract reads:

"Thermal insulations made of fibers, powders, or porous gels are characterized best with respect to their infrared optical thickness, (i) In optically thick insulations, where diffusion of infrared radiation occurs, the contributions from solid conduction and radiative transport are superimposed additively. (ii) For optically thin insulations a complex coupling mechanism causes the total heat transfer to be larger than the sum of the components; this holds especially for low emissivity boundaries. In this paper recent progress in the investigation of evacuated thermal insulations is reviewed."

Also take a look at this: http://books.google.com/books?id=miXWZMuRE_8C&lpg=PA460&ots=uy_uvEhgGo&dq=aerogel%20infrared%20%2BMie%20%2Bscattering&pg=PA460#v=onepage&q=aerogel%20infrared%20+Mie%20+scattering&f=false

"simple approximation of the full integro-differential energy equation describing the coupled radiative-conductive heat transfer"

[edit: pretty much that whole book is available to read - if you go to page 26 there is a paper which models multi-cavity reflective insulation and has all sorts of interesting equations which describe their behaviour - together with some test results for different configurations. The maths is quite complicated using low-order polynomial equations as well as iterative equations where there is more than one space between foils. This taken together with the radiative component equation that's shown in the aerogel paper should provide the definitive physics for this hugely long thread ]

Seem like people in the physics world have been working in this field.

Paul in Montreal.
- CommentAuthorSaint
- CommentTimeJun 4th 2010 edited
.
- CommentAuthorSaint
- CommentTimeJun 4th 2010 edited
deleted
- CommentAuthorSaint
- CommentTimeJun 4th 2010 edited
Posted By: Saintthe relatively minor scope of its influence at these temperatures
Platinum EPS's 0.31 is an extremely significant hike over ordinary EPS's 0.38 - puts XPS out of the running - hooray!

Tom, it makes a very average thermal insulation less average. Notice its that 20% improvement again similar to what you get with XPS. Roughly in line with what I learned years ago as being the contribution to thermal resistance from the radiation component and no I still can't find the reference.
As for XPS against EPS, I'd take XPS any time. Far less moisture pick up, higher tensile strength important for sandwich panels, higher compressive strength and less compressive creep important for floors. More expensive though

HOORAY I got the quote to work!!!
- CommentAuthordjh
- CommentTimeJun 4th 2010
Posted By: fostertomI'm not disputing that aerogel works - just that it's performance is theoretically inexplicable

Nonsense. There's a good explanation. You really think NASA would put people's lives at risk with it if there was something they thought was "theoretically inexplicable"? Next you'll be asking me to believe that the flying spaghetti monster doesn't exist.

Check the recent links to theses I posted for the one about small cell size. Only a hundred pages or so and I'm sure it'll have the explanation in there, with references. I've also posted multiple links to aerogel technical info previously, so please do some research instead of expecting everybody else to do it for you.

Posted By: fostertoma link wd be gd practice

That'll be useful to quote back at you next time! Thanks
- CommentAuthorCWatters
- CommentTimeJun 4th 2010
There are several good articles on how aerogel works on the web...

http://eetd.lbl.gov/ecs/aerogels/sa-thermal.html

http://www.aerogel.com/features/termal.html
- CommentAuthorSteamyTea
- CommentTimeJun 4th 2010 edited
Posted By: djhflying spaghetti monster

Do they hatch on trees?
- CommentAuthorfostertom
- CommentTimeJun 4th 2010 edited
Posted By: djhI guess you think that ... faster heat transfer will result in faster temperature changes when conditions change
Didn't mean that, didn't say that - read it again, cos you still haven't got the point.
Posted By: djhthat's not the case ... Heat flows at some rate (watts) and that flow has to be collected over some time to raise the temperature of the material it is flowing through
Course I know that.

I'm not saying anything about heat flowing or accumulating either faster or slower.
I'm saying that when a previously steady-state delta-t is disturbed (say suddenly increased) between one wall and the opposite wall of a gas-filled void, heat transfer is increased and continues until a new equilibrium is established.
That heat transfer is by a mix of convection, conduction and radiation, and all three modes begin instantly to transmit additional heat from the hot wall.
But it takes a while before any additional heat starts to be received by convection and conduction at the cold wall - the cold wall doesn't 'know' its temp is about to be re-equilibriated until some of the additional heat flow starts to reach it.
However, radiation is different. Additional heat starts to be received by radiation instantly at the cold wall - the cold wall instantly begins to get its temp re-equilibriated. Indeed it may have become fully re-equilibriated before the convection and conduction get there. In that case, radiation has been responsible for the entire re-equilibriation, and convection and conduction will have played no role.
Note, this says nothing about heat flowing or accumulating either faster or slower - it could be either of these, for all I know. I'm talking about which one of the three does all or most of the work of re-equilibriation, when steady-state is disturbed, in materials that have pores or void spaces within them.

PS I do intend to follow up all the links, and prob amend some of my views, asap.
- CommentAuthorPaul in Montreal
- CommentTimeJun 4th 2010
Tom,

what you're describing is correct - the issue we have been taking you to task for is your claim that radiation dominates. The aspen aerogel link gives the equation to calculate how much the radiative component is and it's not dominant at the sort of temperatures insulation in buildings is used at (very different in the aerogel that's used in the tiles on the space shuttle). One of the other references I gave has iterative equations to calculate the heatflow through mult-cavity reflective insulation (i.e. multifoils) - the iterative nature of these equations does correspond somewhat to your thought experiments but are more rigorous in their mathematical analysis (and also include polynomial equations to describe the conductive and convective effects of the spaces between the reflective layers).

The point being is that there's no mystery science going on here - the properties are well understood and can be calculated. It would be impossible to design the heat shields on the space shuttle if this was not the case - this just being an extreme application of such materials (ok, the gels there are not reflective, but the radiation transmission properties are very important). The thing that frustrates many is that the reflective insulation industry has made many overstated claims on their products' performance which are not borne out in real-world buildings. There's nothing intrinsically wrong with the products, but that should not be sold on the basis of misleading claims. If part of their performance comes through the requirement to provide good airtightness, that's not a bad thing per se - but to claim that there's some kind of special physics going on which makes these products have qualities that they do not is disingenuous at best and bordering on the fraudulent at worst.

As has been pointed out in other threads, once you get beyond around the equivalent of 6" foam insulation with good airtightness, you've already reduced the heatloss by about 95% of the uninsulated case and any extra is really in the realms of extreme diminishing returns that's not a good ROI. But understanding that part is all about the right engineering compromise - as the threads about thermal bridging demonstrate. It's like a restatement of Amdalhl's laws of the speed-ups offered by parallel processing in the computer world: a system is only as fast as the slowest part.

Paul in Montreal.
- CommentAuthorfostertom
- CommentTimeJun 5th 2010
Posted By: SaintAs for XPS against EPS, I'd take XPS any time. Far less moisture pick up, higher tensile strength important for sandwich panels, higher compressive strength and less compressive creep important for floors. More expensive though
if you need those qualities, sure. if you don't, then EPS is as you say much cheaper, and very important - breatheable. It also has AFAIK much better eco-virtue than any blown plastic insulation - but I haven't got documentation on the latter - can anyone explain/provide a link?
- CommentAuthorfostertom
- CommentTimeJun 5th 2010 edited
Posted By: Mike Georgethe original in-situ tests carried out by Actis et al showed multifoil in such a good light largely because of the superior air tightness of multifoil over mineral wool
Can't be, Mike. Actis' Tri-Iso 9 was (like today's Tri-Iso 10) held together with quilt through-stiching. If you add up the area of the stitch holes (which are not blocked by the thread), it's equiv (if I remember) to a 70x70mm clear hole to every m2. Tri-Iso, like most multifoils, is incapable of being airtight. If you hold a bit to your mouth you can breathe through it with no effort!

Posted By: Mike Georgethere seem to be very few peer rieviewed publications looking specifically at heat loss through multifoil. If all of this were so easilly explained then why is that?
I think, and I'd have thought you'd know too, that Paul Mitton and the CMM were keeping their data and results non-public because involved in delicate negotiation with the testing houses, against powerful opposition from the conventional insulation manufs. Since CMM seem to have accepted political defeat, who's going to bother to publish stuff that just might be needed to a fresh attempt sometime?

Posted By: sainta ridiculously naive and cheap test carried out by a manufacturer who was singularly ignorant of the installation techniques of the very competitive materials they were intending to malign
Who sez? Can you substantiate that?
- CommentAuthorSaint
- CommentTimeJun 5th 2010
Posted By: fostertom
Posted By: SaintAs for XPS against EPS, I'd take XPS any time. Far less moisture pick up, higher tensile strength important for sandwich panels, higher compressive strength and less compressive creep important for floors. More expensive though
if you need those qualities, sure. if you don't, then EPS is as you say much cheaper, and very important - breatheable. It also has AFAIK much better eco-virtue than any blown plastic insulation - but I haven't got documentation on the latter - can anyone explain/provide a link?

Tom, EPS has a higher resistivity to moisture vapour than brickwork which is typically the component that we're trying to allow to breathe so I would argue its "breathable" credentials
- CommentAuthorfostertom
- CommentTimeJun 6th 2010
EPS is still way down in the bottom league of resistivities (unlike XPS and all the blown plastics - except Icynene) and checks out well in Euler condensation-checks as part of breatheable constructions. And the figure for Springvale Platinum EPS is much lower than the generic EPs figure that's usually quoted.
- CommentAuthorbiffvernon
- CommentTimeJun 6th 2010
Posted By: fostertom held together with quilt through-stiching. If you add up the area of the stitch holes (which are not blocked by the thread), it's equiv (if I remember) to a 70x70mm clear hole to every m2. Tri-Iso, like most multifoils, is incapable of being airtight. If you hold a bit to your mouth you can breathe through it with no effort!

Does that mean my woolly jumper won't keep me warm?
:(
- CommentAuthorSteamyTea
- CommentTimeJun 6th 2010
Biff

It should in June
- CommentAuthorfostertom
- CommentTimeJun 6th 2010 edited
Posted By: biffvernonDoes that mean my woolly jumper won't keep me warm?
Why should it mean that? What it does mean is that none of its insulative effect can be attributed to airtightness - luckily.
- CommentAuthororangemannot
- CommentTimeJun 15th 2010
Anyway anyway, having scanned a small %age of the above I picked up on the "anything more than 150MM foam equivalent" approximating to 75% is chasing a very rapidly deminishing return.
Howqever however, we all live in the real world with its builders/workmens "bodges"
I would for instance refer to the bad press flat roof got
Despite the integrity of the reasearch & the intrinsic quality of the material
All for naught due to poor installation
- CommentAuthorbiffvernon
- CommentTimeJun 15th 2010
Integrity of the research? It failed to integrate the observation that it rains. Flat roofs are for deserts.

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