thanks tom for your response, very enlightening and completely understandable.

it seems to me to be a direct comparison to a thermos flask.... the reflective inner surface reflects the majority of the heat radiation back in because theres very little heat loss throught convection or conduction because its surrounded in a vacuum.

However, it still doesnt answer the question as to how much heat energy is actually lost FROM A HEAT SOURCE by radiation.
Conversion of heat into radiation is determined solely by the temperature and characteristics of the substance emitting the radiation... case in point a concrete slab with UFH. surely the majority of heat loss through this element is by means of convection and conduction, and a minimal by radiation. The amount of energy in the radiation is also a factor in the extend of heat loss... ie the concrete slab offers a minute of a degree of radiation the sun offers... Radiation heat loss is also reduced at every point the em radiation hits any surface, be it a chair in the room, curtains etc, and is converted back into conduction heat loss. Many surfaces have natural radiation emissivity,many modern paints, renders etc... all of which reduce the need for radiation reducing emissivity in an insulating product.

Tom,
I can't do the "posted by" cut and paste bit for some reason so I'll have to answer as best as I can

I'm not arguing that multifoils don't work its just that I've yet to feel comfortable with any explanation of why they are supposedly much better than anyone thinks. In fact I was enjoying a rather esoteric experience following your analogies to warm and distant shores. That was until you remarked that the distant shore heated up quickly due to radiation such that there was no thermal gradient ...I'll have to think a bit more on that, I started to feel a little too warm.

As for received authority, not quite sure what that means. My only authority is limited to age (more than I wish) and experience (painful)

Multifoils in Space and Cryo yes but aren't they almost always associated with evacuated space and vacuums?

Sure SIG's core business is stockist/distribution but over the years SIG has owned and divested itself of many diverse manufacturing companies, "Knobs and Knockers" comes to mind although that could well be before your time

Euroform have an impressive external cladding products range from simple building boards to architectural panels and fire protection boards under the brand name Versa, that's the attraction. SIG already have distribution agreements for the major foil manufacturers with dominant market share so why would they want to buy a smaller scale manufacturing operation that would upset their major suppliers. XFoil just came along too

Posted By: Saintone question must be if multifoils are so good then why has there been so little penetration into other applications and industries?

Maybe other industries employ physisists and so aren't so easily hoodwinked by bad-science.

haven't read all this thread , lifes to short , but has anybody stuck one of those thermal imagining cameras on a multifoil insulation job
and compared it with a Pur/pir or mineral wool job
that should give you quick idea how well it works in comparison ?

pop up hell!

What's the best file sharing/upload site?

Posted By: fostertomWe all need a supply of bad science to keep us interested. Where do you get yours, Biff?

Oh, some Tom, Dick or Harry. I think it was Tom.

Posted By: sinnerboyi find yousendit is good

Seems not to be an upload warehouse, like Photobucket, that I could give a link to on this page. Any other suggestions?

tom, http://www.box.net/ is also good for uploading

matt, your practical experience holds a lot more weight than some of the theoretical arguments put forward in this thread.... thank you for this... it also conforms with most of the conversations ive had with people who have this installed in their roofs.

Posted By: Mike GeorgeMatt, you don't perchance sell natural insulation do you?" alt="" src="https:///newforum/extensions/Vanillacons/smilies/standard/wink.gif" >

Damn, rumbled!

I do hope you will believe me on this one, that I am not that impressed with the MF insulation - and thats after investing £1500 and a couple of days of damn hard work.

Prior to selling stuff for NBT, I worked doing full house renovations and attic conversions (I must have done a dozen attics), and I still visit a couple of the attics at friends houses I converted / re-converted. Mine is the only one I am not happy with

For me all insulation is good , but MF is the only one I have misgivings about at present....

Its stuck between your two shores....I'm still puzzling

Tom,

Not being picky but two obvious questions:
1) Why no vapour barrier on the warm side of the mineral wool. With the temp differential there's a strong vapour drive, condensation likely on outer face of mineral wool and interstitially? heat drain?
2) How long had the products been installed before the test was carried out?

Yeah I know Saint, lots of Qs spring to mind - let's hear them!

To me, despite everything it's interesting that the MF shows as at least in the same league as the GF, which is all that anyone's claimed, and is something, considering it's 30 vs 200 thick. Also the differing timescales of heat flow - my guess is that at times the flow through GF will be far less than thro MF; at other times the reverse.

Despite its flakiness I'd say this test is at base truer than that outrageously client-serving NPL report. The NPL scientists claimed to have tested the idea that MF thrives in 'dynamically varying' temp conditions, as opposed to the steady-state that the hotbox test goes to great lengths to establish. They did that by allowing the hotbox temp to change over quite a long period - hours I think - and found it made no difference to MF's usual pathetic hotbox performance.

The point is, it was still the hotbox, which does apparently succeed, against all natural odds, to establish something close to unperturbed steady-state. Simply varying that unperturbed near-steady-state over a long cycle has no resemblance whatever to the rapid minor fluctuations that happen in the real world - the ones induced by everyday temp events as I listed above, let alone the ones caused by more microscopic events, right down to quantum.

So it's no surprise that the NPL was able to dismiss that 'dynamically varying temp' cornerstone of the story of how MF works. If NPL had bothered to consult the MF manufacturers' scientists, they'd have learnt what 'dynamically varying' should mean.

In that fundamental respect, this flawed test-shack experiment is far closer to reality, allowing MF to function as advertised, than ever occurs un the hotbox. The European testing community has accepted the MF manufacturers' evidence on that, which is why there are currently 13 very expensive new-style test rigs under construction across Europe (while US, Canada and Australia have agreed to suspend judgement), that are instrumented to number-crunch the data of insulation tests under dynamically-varying temps. In other words, the hotbox's days are numbered and the conventional insulation manufacturers are looking forward to some embarassing revelations.

It's not that MF matches the advertised k-values of conventional insulants - more that all insulants' k-values have been highly overstated for decades by the unreal conditions of the hotbox test.

And it may be that at some moments MF loses heat horrendously, but balanced at other times by losing almost none at all. MF performance claims have always been on the basis of totting up actual energy used over a complete heating season, and on that basis seem to do very well.

For decades, insulation manufacturers have made fortunes by selling products that are 'test-box specials', designed only to do well in the hotbox, and not checked against real life. It's incredible that the blinkered artificial 50yr old slide-rule era procedures of the hotbox are so vigorously and uncritically defended as 'scientific', while real-life tests of actual buildings over a whole heating season are nit-picked to death - without anyone even saying ' it may have been a flawed test, but there's something here to be looked at properly'. That kind of open disinterested curiosity would be what I call 'scientific'.

There's a point - unless they used a propane burner as the heat source, where did that moisture come from, to cause condensation? Not from any of the usual domestic sources, not from water stored in the fabric. The test seems to have been done outside on a cold day; at start inside air must have been same as outside: non-water-generating heat source would then have lowered, not raised internal RH - so what caused that condensation observed?