Experimental and numerical investigation of the fire behavior of double-glass building integrated photovoltaic modules with PVB interlayers

Amid rising global energy demands and environmental concerns, energy-efficient, or ‘green’, buildings are becoming mandatory in building regulations worldwide. In that context, building-integrated photovoltaics (BIPV), which merge photovoltaic (PV) modules with architectural design, are gaining widespread adoption. To assess fire safety aspects of BIPV, the fire performance of double-glass PV modules with polyvinyl butyral (PVB) encapsulation in BIPV façade systems was studied experimentally and numerically. More specifically, fire experiments were conducted under varying radiative heat fluxes to evaluate thermal degradation, fire behavior, and toxic gas emissions. Key parameters, including ignition time, heat release rate per unit area (HRRPUA), mass loss rate (MLR), and gas composition, were analyzed. The results confirm that a higher external heat flux markedly reduces ignition time while increasing HRRPUA and MLR for BIPV, which is in line with results for other materials. The primary toxic gases emitted during combustion were CO, CO₂, H₂, and SO₂, with CO and CO₂ emissions rising significantly at elevated heat fluxes. To complement the experimental results, a numerical model coupling transient heat conduction and pyrolysis kinetics was developed to predict the pre-ignition thermal response of the multilayer structure. The model employed layer discretization and temperature-dependent boundaries, demonstrating close agreement with experimental data. Therefore, it enabled systematic analyses of the sensitivity of PV module material flammability to incident radiative heat fluxes, material properties, and geometric configurations. This combined experimental and numerical approach offers a predictive framework for assessing fire risks and optimizing the fire safety design of BIPV systems. © 2025 The Authors