Upward flame spread behaviour of cladding materials on a medium-scale ventilated façade

A parametric experimental study was performed to characterise the phenomena governing the upward flame spread dynamics in a simplified ventilated façade using a medium-scale testing rig. The ventilated façade was comprised of an insulation foam (INS) and an aluminium composite panel (ACP) with a cavity between the two materials. Two different cavity widths (0.10 and 0.15 m), two INS products (Polyisocyanurate (PIR) and Phenolic (PF) foams) and two ACP cores (Polyethylene (PE) and Polyethylene based with fire retardant (FR)) were tested, for a total of 8 configurations. The experimental medium-scale set-up provides a fundamental understanding of the interactions between insulation materials and ACPs in fire growth in ventilated façade systems. High instrument density allows the use of bench scale flammability data to interpret the materials’ contribution to the total HRR and analyse overall results. The study suggests the possibility of developing a comprehensive framework to assess fire performance of different material combinations and system layouts, improving fire safety standards in construction. Loss of encapsulation integrity was found to accelerate fire growth and flame spread on combustible linings. PIR and PF insulation materials contribute earlier to HRR and fire growth compared to ACP cores, with PIR contributing more. The smaller cavity width was observed to enhance the flame spread over the linings, with sustained spread in all cases whereas in the larger cavity width there were cases with unsustained spread. A fire growth parameter ( γ ) was quantified, with γ < 0.005 indicating unsustained spread over the linings, and values between 0.005 and 0.018 signifying sustained spread. The Cladding Materials Library framework enables reliable interpretation of observed behaviour and interactions between the materials studied and a fire within the cavity. • Insulation foams drive early fire growth with a narrower cavity width enhancing flame spread. • A fire growth parameter ( γ ) has been proposed to quantify sustained spread in façades. • A simplified framework explains how cavity width and materials affect fire spread.