Burning behaviour of rainscreen façades

Four reduced-height (5 m) BS 8414-1 façade flammability tests were conducted, three having mineral-filled aluminium composite material (ACM-A2) with polyisocyanurate (PIR) and phenolic (PF) foam stone wool (SW) insulation, the fourth polyethylene-filled ACM (ACM-PE) PIR insulation. Each was constructed from a commercial engineer’s design, built by practising installers. The ACM-PE/PIR burnt so ferociously it extinguished after 13.5 min, for safety. ACM-A2 cladding panels lost their structural integrity, melted away test wall, whereupon around 40% of both combustible PF insulation contributed to fire spread. This demonstrates why all products must be non-combustible, not just outer panels. For tests, while temperature in front cavity independent temperatures within varied greatly, depending on system using PF/A2 allowed break through first, as seen sharp increase 17 min. PIR/A2, increased sharply at 22 minutes, panel started fall wall. SW/A2, no rapid rise observed.