Small-scale experimental study on EPS ETICS and flame-retardant coating reaction-to-fire performance

External thermal insulation composite systems (ETICS) are a common and energy-efficient cladding system. Thermoplastic expanded polystyrene (EPS) is widely used as an insulation core. However, such combustible material has aggravated fire incidents in recent years, thus it is essential to improve its fire behavior. To evaluate the performance of EPS ETICS, a series of specimens with different flame-retardant (FR) coatings were tested using a small-scale bench and a mass loss calorimeter with a maximum heat flux of 40 kW/m². When untreated EPS ETICS are exposed to heat, the EPS foam degrades, releases a large volume of combustible gases, and ignites. Applying FR agents such as FR surface paint and expandable graphite blended coating can stop flame propagation, reduce total heat release by approximately 50%, and preserve about 50% of the EPS foam during heat exposure. This enhances significantly the fire safety of EPS ETICS.