post Grenfwll insulation options

The aluminium/polyethylene rain screen burnt at a temperature far higher than a normal domestic fire would achieve, and in a domestic situation the PIR would be hidden behind plasterboard or similar anyway (hopefully).

I thought this was the reason why the PIR actually *contributed* to the fire ?.

The kingspan did burn because the rainscreen burnt at closer to a 1000C, which PIR would never be exposed to in a domestic fire. ITV news actually demonstrated Kingspan burning furiously on a test rig at this high temperature.

Grenfell has a non-smooth external appearance, so getting rigid pir to fit closely to eliminate cold air incursion between building and the warm side of insulation is almost impossible. Rockwool should have been used and the external rainscreen would have probably burnt off without any significant incursion into the flats (but there was the issue of DG windows fitted with or sealed with foaming PU adhesive).

This will not generate the 1000C heat that burning aluminium is capable of. This is the problem.

Ive had the f****ng stuff RED HOT and it STILL wouldn't burn I think there is some covering up going on.

I wonder of it was PIR. As I said, Ive got it really really hot and it wouldnt burn

Rockwoool absorbs water and becomes totally useless

So the real issue was the cladding. Not the PIR.

Yes, grenfell hasn't put me off using PIR in a SIPs build.

Still not hot enough because you have no means of generating a temperature of close to 1000C, unless you have some bits of old magnesium /aluminium gearbox and create a fire with that.

No the real issue was the wrong choice of insulation. Rockwool would have moulded more easily against the angular face of the building prventing air leakage into the junction of the warm side and the outer face of the building.

Apparently 18 metres is the official limit. That's about seven stories.

Fire retarded - harder for them to catch fire but once on fire giving off more lethal gasses.

There is hot and there is hot... metal fires with a massive updraught of forced air in a cavity will burn at very high temperatures - think smelting/forging temperatures not blowtorch temps.

More than likely - although I expect this is a case of lots of group decisions without anyone fully analysing the bigger picture, and looking at the risks as a whole.

I doubt there were any "quick fixes" here where one change would have changed the outcome significantly.

It would need a different screen material, fitted in a different way, with different detailing. Added compartmentalisation, possibly different windows and window fitting techniques. Better fire protection, better detection systems, better fire suppression systems. Different day to day operating procedures, and different emergency escape procedures. Better protected escape routes.

This is before you add in all the external motivations for cladding it in the first place (better building appearance, improving the appearance of the area, lower heating costs, "net zero") etc.

Its very easy to get to 1000°C

That's about the melting point of brass.

Fuel Flame Temperature Blowtorch 1,300 °C (2,400 °F, air) Bunsen burner 1,300–1,600 °C (2,400–2,900 °F, air) Butane 1,970 °C (air) Candle 1,000 °C (1,800 °F, air)

And once wet, would have been as much use as a chocolate teapot.

No. Materials that produce lethal gasses are now illegal to sell.

Typically polyurethane rubber foam.

Not my experience at all. A little soot, and that was all.

and the grenfell cladding formed tall chimneys which did

Well yes. My point is that everybody is pointing the finger at the PIR foam. But by itself it couldn't have dine that. It was the cladding. But no one seems to be blaming it.

When casting in sand the temperature is taken well above the melting point to ensure it doesn't start solidifying before it has flowed into a mould.

It was the cladding, that's what gets the blame.

But what also gets blamed is the building safety industry, including manufacturers (Kingspan, Celotex, Arconic), assessors (BBA, BRE, LABC) and government (bonfire of red tape, light touch regulation). The Grenfell report shows that the system was rotten from top to bottom.

In the context of the OP's question, the evidence showed that Kingspan and Celotex/Saint-Gobain did things to suggest their products were safe for high rise buildings when they weren't, had passed tests they hadn't, advertised testing from the old formulation without getting the new formulation retested, and straight up rigged the testing.

Chapters 22-25 if you want some bedtime reading:

"22.5 Phenolic foam is an organic polymer, so whatever blowing agents or methods are used to produce it, it is not a material of limited combustibility as defined in Approved Document B.435 With the exception of Dr Rochefort, who professed not to have been aware at the time of the fire performance of K15 or the existence of a definition of limited combustibility in Approved Document B,436 all the Kingspan witnesses from whom we heard confirmed that they had been aware throughout their employment at Kingspan that K15 was not, and never could be, a material of limited combustibility.437"

so irrespective of any fire retardants put it in, it is not suitable for use on high rise buildings. End of story.

Theo