The evolution of the construction sector towards industrialization is driving the adoption of lightweight, prefabricated multilayer modular and preassembled envelope systems. This offers advantages in quality, execution speed and technology integration. However, their fire performance remains a critical challenge. While the Single Burning Item (SBI) test is commonly used to assess fire reaction, it often fails to capture the actual fire behaviour of complex façades. This study introduces a novel methodology for evaluating fire performance that goes beyond standard testing requirements to meet more stringent safety criteria. The approach identifies critical areas in heterogeneous façades where fire propagation is difficult to predict. Then it was applied to a 2.2 m × 3 m façade module incorporating photovoltaic (PV), solar thermal (ST), and hybrid PVT technologies. Intermediate-scale testing was developed as a modified version of ISO 13785-1, featuring increased burner output (from 100 kW to 300 kW), altered specimen configuration (from two-wing to single-wall), and the establishment of evaluation criteria. Two experimental tests were conducted. The first failed to meet any criteria, while the second, with design improvements and passive fire protection, met all but one (burning falling parts). The findings emphasize the importance of early-stage fire performance assessment and iterative design refinement. They also reveal that a favourable fire reaction classification does not necessarily ensure acceptable fire spread behaviour, highlighting the need for more realistic testing methods. Intermediate-scale testing is proposed as a valid, cost-effective tool for fire performance evaluation. Future research should deepen correlations with full-scale tests and explore calorimetric analysis and cost-benefit assessments of fire protection strategies. • Fire safety was introduced in the design of a multilayer modular façade system • Medium-scale fire test procedure and evaluation criteria were developed • Two tests with different passive fire protection measures were performed • Implementation of protection measures significantly improved fire behaviour
Aurrekoetxea-Arratibel et al. (Sun,) studied this question.