DH carried out a simple and completely unscientific experiment this morning
We have a small sheet of the insulating material used in the cladding on Grenfell Tower. He lent it against a wall and applied a blow torch to it. The material was quite slow to ignite and when he took the blow torch away, which he did several times, the fire soon fizzled out, suggesting that the material itself while flammable quickly self quenches when the source of the flame is taken away.
The difference between his experiment and Grenfell Tower, apart from scale, is that the panels were fixed to the walls of the tower with an air gap between the insulating material and the walls of the tower. This air gap acted as a chimney between insulation and wall and the fire was fed and spread by the suction of the 'chimney' and the presence of air.
This effect would have been there whether the insulation was totally non-combustable, partly flammable like the piece of the material DH used, or highly inflammable and suggests that the inspection of cladding on tower blocks should go beyond just checking on the material used but on whether there is an air gap between cladding and the previous outside wall of the block. If there is a gap, then fire breaks should be installed at regular intervals so that the chimney effect that led to the spread of the fire cannot occur again.
I think too much of the publicity about the cause of the fire has been put on the cladding and not enough on the extent that the fire was channelled from floor to floor by defects in the building services that had cable conduits and other services that were continuous from floor to floor without fire breaks at regular intervals and, of course the air gap behind the claddng.
