Part 11: Matters outstanding from Phase 1

Chapter 108: Introduction to Part 11

¶108.1 In the Phase 1 report the Chairman concluded that, although there were many different factors, the main reason why the flames spread so rapidly up Grenfell Tower was the presence of ACM panels with polyethylene cores which melted and acted as a source of fuel for the growing fire. He also concluded that it was more likely than not that the presence of polyisocyanurate (PIR) and phenolic foam insulation contributed to the rate and extent of the vertical spread of flame, but that it was not possible at that stage to quantify their respective contributions.²⁰⁶³²⁰⁶³ Phase 1 Report, Volume IV, paragraph 23.52. He indicated that further work would be done during Phase 2 to gain a better understanding of how the materials behaved in conjunction with each other when exposed to fire. Further work also needed to be done to understand the extent to which exposed edges of the ACM panels and insulation boards may have contributed to the spread of flame.²⁰⁶⁴²⁰⁶⁴ Phase 1 Report, Volume IV, paragraphs 23.52 and 32.62.

¶108.2 In order to reach a better understanding of those matters, at our request a series of experiments was devised by Professors Bisby and Torero which were carried out by Professor Bisby and his colleagues at Edinburgh University. They included testing each material or product in isolation in order to understand its particular burning characteristics, followed by the testing of a series of models designed to shed light on the behaviour in fire of a ventilated rainscreen external wall system containing materials of the kind used on Grenfell Tower. The experiments were designed to enable them to identify the properties of both the individual constituents and the system as a whole that were most relevant to the growth and spread of fire at Grenfell Tower.

¶108.3 The work carried out by Professors Bisby and Torero is described in detail in their reports.²⁰⁶⁵²⁰⁶⁵ Bisby, Phase 2 Materials Testing Report {LBYMT00000002}; Bisby, Phase 2 Experiments Work Package 1, Regimes of Burning {LBYWP100000002}; Bisby, Phase 2 Experiments Work Package 2, System Interactions {LBYWP200000001}; Torero, Phase 2 Report {JTOR00000006/66-78} paragraphs 9.0.1- 9.3.16. Professor Bisby also gave oral evidence about it.²⁰⁶⁶²⁰⁶⁶ Bisby {Day289/105:10}-{Day289/186:20}; {290/9:11}-{Day290/84:2}. In the space available to us we cannot describe their work in detail, but we have sought to draw out the important conclusions that emerge from their experiments. We are extremely grateful to Professor Bisby and Professor Torero and to all the others who were involved in helping with the experiments. The work they have produced is immensely valuable and helps to explain what caused the rapid spread of flame over the external wall of Grenfell Tower. We hope that the information derived from their experiments will assist others who may be designing ventilated rainscreen walls in the future.

¶108.4 At the end of Phase 1 there remained a degree of uncertainty about the mechanism by which the fire escaped from the kitchen of Flat 16 into the external wall as a result of a reconstruction carried out by BRE. The chairman indicated that when the full information had become available he would ask Professor Bisby and Professor Torero to prepare supplementary reports. That they have since done, as described in Chapter 110.

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