Basicalliy it's saying:

1) that the foil mentioned (see * below) isn't as good as 100mm mineral wool (let alone 200mm mineral wool).

2) that hot box test figures should be used to calculate U-Values... " no new substantive evidence on robustness,
accuracy, and repeatability to support the move from hot box characterisation to in-situ performance testing is presented".

3) Chapter 5 hints at the future of multifoils. Section 5.7 - 5.15 are interesting as they attempts to calculate the best that a new multifoil could ever achieve. For example it proposes a multifoil that uses aerogel (see $ below) but 5.15 concludes.. "...multi-foil systems even if using the best materials available cannot out perform 200mm of mineral wool insulation for the roof structure simulated".

Why they compare with mineral wool I'm not sure. I thought rigid foam insulation was better than mineral wool at same thickness. Isn't thickness the whole point?

Notes:

* = "a multi-foil insulation with aluminium relective surfaces, (emittance 0.07) and a core thermal conductivity of 0.04"

$ = "multi-foil systems with relective surface emittance of 0.02 and foam core thermal conductivities of 0.012W/mK (aerogel blanket)."

Posted By: CWatters" no new substantive evidence on robustness, accuracy, and repeatability to support the move from hot box characterisation to in-situ performance testing is presented"

Incredible that a 'reputable' organisation can base policy on a flat lie. Reams of such evidence has been produced, and was accepted by the consensus of the testing houses of Europe, who consequently embarked on a programme to build 13 expensive new test rigs. However the trade-protection battle continued and the 'conventional' insulation manufacturers managed to scotch that programme. The multifoil manufacturers seem to have accepted defeat for the time being - at least, Paul Mitton of Euroform (Xfoil), the boffin leading the charge, now has his hands full as MD of Euroform under its new owners Sheffield Insulations. However SIG didn't pay £8m for Euroform just to see its flagship product line extinguished, so I'm sure the story's not over.

Posted By: CWattersmulti-foil systems even if using the best materials available cannot out perform 200mm of mineral wool insulation

not true - just to prove the point, Paul Mitton produced a testbed special multifoil that comfortably out-performed the mythical 200 min wool even in the hotbox. All conventional insulations are in fact testbed specials, designed solely to excel in the artificial conditions of the hotbox test, without (perish the thought) any verification under real-life conditions.

Posted By: biffvernonhe went very quiet when I asked him a queston he didn't like

so did you Biff - you've stonewalled any response to my answer to your key question 'what do layers 2-6 do?', upon which your scepticism about MFs depends.