<blockquote><cite>Posted By: biffvernon</cite>Thermal performance — when combined with other types of insulation</blockquote>

I caught that one, you could get a BBA cert for anything as an insulator then? as long as "combined with other types of insulation"

"new all improved 'Mars bar wrappers', space age insulation (Mars - space...? eh..? eh...? ... sorry...)... Certified to archive a U-value of 0.1!...."

(small print: "Depending on the construction method and when combined with other types of insulation...")

Seems to me that Actis et al were have tried to take on the David vs Goliath, Linux vs Windows sort of mantle we all love to stick up for. Yup no doubt in my mind that Kingspan + Celotex will make insulation out of their Grannies if it would flog a few more sheets, but that doesn't automatically make Actis not bent as butchers meat hooks when it comes to testing etc. You never know there might be miracle cures out there and we should keep an open mind but to be honest I don't think its likely (no I can't can;t support that statement with scientific evidence!) - till then it remains easy said than done to save the world!

J

Posted By: James Nortonbent as butchers meat hooks when it comes to testing etc

Can't speak about Actis, but no-one who's had chats with Paul Mitton would doubt the integrity of his extensive multifoil testing and development. As Tech Director of little Euroform he was stepping in where wealthy Actis should have lead, in the CMM (Confed of (UK) Multifoil Manufacturers)'s scientific campaign to get the European accreditation organisations to introduce methods capable of testing multifoils under the 'real life' conditions in which they excel. As a result, against all the non-scientific influence that the conventional insulation manufacturers could muster, CMM's scientific case was accepted and a 5-yr programme was instituted to build 13 very expensive dynamically-varying temp test rigs across Europe (the flaws in the trad steady-state hotbox methodology having been demonstrated). Also SIG (Sheffield Insulations) paid £8m to acquire Euroform - the only insulation manufacturing co. (as distinct from re-processor/distributor) they currently own. No amount of 'skeptic' rhetoric and suggestive slander will alter either the statement of 1st sentence above, nor the two expensive statements-of-faith of the last 2 sentences above.

..

Posted By: TimberSo, the out and out air leakage performance of the origional TRADA tests is unknown.

Probably known, but not published. The GenX material is also completely different to that originally tested [actis?] by TRADA, so not really fair to draw a comparison.

I should declare that I have done some consultation work for Euroform in the past, but only Dynamic Simulation work, with results which are not yet certified in any way or for that matter fully understood.

Posted By: James NortonSeriously(!) though, round of applasue as the thread tops 450, shall we have a party at 500?" alt="" src="https:///newforum/extensions/Vanillacons/smilies/happy/clap.gif" >

Are you buying? where to?

Posted By: fostertomMy own understanding, that I've offered here several times - might do it again, if anyone intetested.

If you can offer it a mere 31 more times Mikes going to buy us all a drink!

Seriously (again) though one of the real issues with this debate is the potential impact on a wider revisit of how we measure the heat loss of buildings and the impact on the basic U-value as not necessarily (to understate) the best method of understanding how much energy a building actually uses in practice. This chimes in with many other strands of recent debate in te real world as well as the forum.

J

Posted By: biffvernonI've never debated it's airtightness, but if airtightness is what you want then it's cheaper to use a sheet of polythene. If you want to combine airtightness with insulation then use bubblewrap.

Aint necesarilly so. Here's a suggestion -the more layers there are, the more convoluted the airpath to the ouside, fill the spaces between the membranes with fluffy stuff - better again - common sense - innit

Posted By: biffvernonMy point has always been that the internal layers of foil in a multifoil are are very expensive way of adding very little insulation.

Not proven, one way or the other. Go directly to the start of the thread, do not pass go, and do not collect £200 [unless the drinks are on you]

Posted By: biffvernonThis BBA Certificate does not alter that point.

It alters nothing, except that the owners of the Certificate have decided that if you cannot beat them, join them. Ie they have complied with the BR443 method [Hot plate] of measuring thermal conductivity.

Suggest we give credit where its due.

Posted By: Mike George

Posted By: biffvernonMy point has always been that the internal layers of foil in a multifoil are are very expensive way of adding very little insulation.

Not proven, one way or the other

certainly not by Biff! whose spreadsheet exercise, as I remember it, never got completed, and only accounted for the 5% of radiant that got through from layer to layer to layer, so obviously got rapidly into diminishing returns (5% of 5% of 5% = 0.0125%), whilst ignoring the 95% that got reflected back, then re-reflected forward, of which 5% got through and 95% went back, came forward again ad infinitum. Once the 95%'s are accounted for and summed, the result is near-linear temp decline from layer to layer to layer - in other words every layer plays a near-equal part, and the more layers the greater the total resistance. Of course, like any insulant, additional layers/additional thickness has diminishing effect, but that's 'normal' diminishing returns quite different from the exponentially vanishing returns that Biff's been aledging for the inner layers.

Er, no Tom. You've not understood. And Mike, airtightness is a red herring. Nothing to do with the essential feature of multifoil. All the BBA cert says is that multifoil is fine so long as you use it with something else - long-johns, base layers, hot-water bottle, the choice is yours. The BBA cert does not say incoporating extra layers of foil within an insulator is good value for money.

Posted By: biffvernonTom. You've not understood

Aha! we have engagement! so - gonna explain what I haven't understood?

Posted By: Mike GeorgeForget the argument about u-values... ...(they) are irrelavant in this context.

Don't give up Mike,

I was just having a laugh, its a good point about the infiltration rates, I suppose the key thing re BBA is that is is not necessarily certifying the material / product as an insulant?

However as a "draught stopper" alone they are horrendously expensive...?

J

PS Anyone any idea how I might actually make insulation out of grannies...?

Yes. Referring back to the start of this interminable thread, I started by being bedazzled by this space-agey material but was sensible enough to consider the theory behind it before spending money. I could not reconcile my theoretical understanding of the physics with my ethusiasm for the product. So I did an experiment. Experiment and observation supported the theory and not my prejudice so I had to change my opinion. Others have conducted more sophisticated experiments and yet others have investigated the theory further.

We are left with very expensive draught excluder.

Posted By: biffvernonI could not reconcile my theoretical understanding of the physics with my ethusiasm for the product. So I did an experiment. Experiment and observation supported the theory and not my prejudice so I had to change my opinion.

I'd really appreciate it, to have you run through that process, or provide links to the (old) forum. I remember there was the cafetiere experiment, and the spreadsheet model. Was there more?

Much later Tony (I think) re-ran the experiment, modified to meet the crits made of your original one. Others too.

Perhaps it's time for all those who've done their own practical or theoretical investigations into multifoil, to join in a concentrated re-summary of what each of us thinks we discovered.

Posted By: NoyersSorry, just helping the thread along to the 500 mark.

A worthy goal.

J



PS

Posted By: NoyersSeriously, would love to see a synopsis of the current thinking.

By the time that kind of agreement is reached we'll be at 1000!

Good god