Experimental investigation of fire spread and heat transfer mechanisms from vegetation to EPS walls under wind conditions

Background Expanded polystyrene (EPS) cladding systems have been used as exterior walls owing to their lightweight properties. Wildfires pose a significant risk to the cladding materials used in buildings, facilitating their spread. Aims To investigate the impact of vegetation burning on the EPS wall under wind conditions. Methods Experiments were performed using 1 and 2 kg of dry vegetation at three separation distances (SDs) from the wall, with low and high wind velocities. Temperature on the wall and the fuel bed was measured, and the radiative and total heat fluxes were measured on the wall. Key results Wall heat flux peaked at 55 kW/m2, while the wall temperature reached 240°C, exceeding the softening threshold of EPS. The fastest fire rate of spread (ROS) was observed at a wind speed of 5 m/s, SD of 30 cm and maximum fuel bed temperature reaching 760°C. Increasing wind speed from 2 to 5 m/s resulted in reduction in total heat flux and wall temperature. Conclusions Under low-wind conditions, separations of 0 and 30 cm pose a risk, particularly when render cracking allows direct exposure of the EPS core to heat. Implications Design and management should prevent 0 and 30 cm distances, to preserve the integrity of the render.