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  1. Andrew, firstly many thanks for doing so hugely detailed work on the technical aspects of the Grenfell fire, I’ve no doubt it will be of use to the upcoming investigations.

    I entirely agree with you about the fact that EU regulations are in no way behind the cause of the fire, it was very much down to our own, as it turns out, rather ineffective and malleable building regulations.

    Some interesting background on PIR insulation that you uncovered. The problem with PIR and PUR, is while they may char, and are less far less dense than the PE in the core of some ACM panels, it is still very much combustible in comparison to incombustible mineral or stone wool insulation, and releases huge quantities of Hydrogen Cyanide, Carbon Monoxide and Carbon Dioxide in a fire. This 2011 paper below from the University of Central Lancashire is very enlightening on this, it shows that only 8g of PIR insulation is required to make 1m3 of air lethally toxic for 50% of the population when burning in under ventilated conditions. and

  2. John, thank you very much for the kind and encouraging words, and for your comment. I am glad you brought it up, since it was one of many pertinent points that I elected regretfully to omit, in the interests of brevity.

    My thinking on it so far is that in a case like that of the tested Celotex RS5000 with non-combustible Marley Eternit cladding tiles – and supposing the classic BRE window breakout scenario – then if the insulation burns to some degree but the fire stays localised – then given that it is burning outside the building the risk to people inside the building – and given that this is presumably a very rare event – the risk from poisoning to inhabitants inside the building might be considered tolerable.

    Or quite possibly it might not. But from the post-Grenfell mass fatality perspective, it seems relatively minor, while we make sure we don\’t have any more Grenfells. But then again, every life is precious and I think this is a very important factor to consider in longer term decisions about external cladding.


  3. Hi Andrew. I think the plastics insulation companies have touted this charring effect as a positive, when really to me it seems merely whitewash or pulling the wool over peoples eyes. The fact is it fails a combustion test at 750 deg c, and according to the UofCL tests combusted at 650 deg c, and released huge quantities of toxic fumes that would very quickly kill people. As many people would have had their windows open and were sleeping I am sure for some it was very quickly lethal. If they were awake and more subject to panic, the CO2 released would also cause more heavy breathing which would have quickened the intake of the Hydrogen Cyanide.

    I think one important factor here is the cavity barriers or lack of. If you look at the uncovered insualtion at Grenfell during construction, you can see the black cavity barriers.

    But to me these do not look like commercially available barriers- they look like fire stopping (non combustible) blocks with intumescent tape stuck, stapled and wrapped on or some worse kind of bodge. I doubt they were any use in stopping the flame extension through the cavity.

  4. Thanks John. Remember that my initial purpose here was to assess claims like ‘the intensity of the fire … was attributable to the polyisocyanurate (PIR) insulation, rather than the cladding’.

    I don’t have a problem with banning combustible insulation if that is what you are proposing. It’s just that I see a slight danger in aiming to high, as it were, and not achieving anything. Better to make sure that we don’t have another mass calamity first, I think.

    As it happens I am inclined to think the best solution for high rise buildings might be to insist on limited combustibility and dispense with the large scale test route. There is nothing wrong with the latter in principle, but it seems to have a tendency to be downgraded to desktop studies supposedly based on real test data for supposedly similar systems. Then follows the natural tendency to backslide, as it were, and become sloppy, as the memory of the last disaster begins to fade.

  5. The photograph from e-architect is good resolution, and better than the extracts I’ve seen from it on the internet. It shows a Cavity Barrier broken at the support rails, and therefore ineffective at the slab edge. It also shows no Cavity Barrier around the windows, and on the right a double layer of Phenolic insulation board. Polyisocyanurate would be a cream colour. I will repost it here.

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