Burning behaviour of rainscreen façades.

Area of Science:

• Building materials science
• Fire safety engineering
• Materials testing

Background:

• Building façade fires pose significant risks, often involving combustible core materials within cladding systems.
• Previous assessments have focused on the combustibility of outer panels, potentially overlooking the contribution of insulation.

Purpose of the Study:

• To evaluate the fire performance of reduced-height building façades under BS 8414-1 standards.
• To compare the flammability of different insulation types (polyisocyanurate, phenolic foam, stone wool) when used with aluminium composite materials (ACM).

Main Methods:

• Conducted four reduced-height (5 m) BS 8414-1 façade flammability tests.
• Tested three façades with mineral-filled ACM (ACM-A2) using PIR, PF, and stone wool (SW) insulation.
• Tested one façade with polyethylene-filled ACM (ACM-PE) using PIR insulation.

Main Results:

• The ACM-PE/PIR façade fire was extinguished early due to intense burning.
• ACM-A2 panels lost structural integrity and melted, allowing significant combustion (approx. 40%) of PIR and PF insulation.
• Phenolic foam (PF/A2) insulation facilitated earlier fire breakthrough into the façade cavity compared to PIR/A2 and SW/A2.

Conclusions:

• The study highlights the critical need for all façade components, including insulation, to be non-combustible.
• The choice of insulation material significantly impacts fire spread and temperature development within façade cavities.
• Stone wool (SW/A2) demonstrated superior performance by not exhibiting rapid temperature rise in the cavity.