Building-integrated photovoltaic (BIPV) modules must withstand various mechanical and thermomechanical stressors to maintain long-term performance and ensure reliability comparable to the longevity of building materials. This thesis investigates the mechanical and thermomechanical stability of lightweight polymeric honeycomb-based PV modules. Two different honeycomb sandwich backplanes with different fiber density and thickness, are studied in large PV modules containing 40 solar cells. The objective is to assess their performance under mechanical loading and thermal cycling through experiments and simulations. Material characterization is conducted using dynamic mechanical analysis, tensile testing, digital image correlation, and optical dilatometry to ensure accurate simulations. Four point bending tests on both pristine and aged samples (10 HF, 200 TC, 1000 DH) show an increase in bending stiffness after aging, while the ultimate load exhibits a slight decrease. These experimental results for pristine conditions are used to calibrate four-point bending simulations, which are then applied to mechanical load testing of large modules. The module with the thicker backplane and higher glass fiber density is white and withstands mechanical loads up to 3.6 kPa without cell fracture or power degradation, exceeding the facade load requirements defined by SIA 261 (1950 Pa for pulling and 1350 Pa for pushing). Simulations indicate that the black colored module with a lower glass fiber density also meets these norms, maintaining mechanical stability up to 2.5 kPa. Thermomechanical testing confirms that both modules comply with IEC 61215, which requires less than 5 % power degradation after 200 thermal cycles. However, the thicker module with higher fiber density experiences interconnector failures after 200 cycles leading to a power degradation of 2.9 %, and a power loss of 11.5 % after 400 cycles. Overall, the study demonstrates that the thicker backplane with higher fiber density and an absolute weight surface density of 3.2 kg/m² provides superior mechanical stability, whereas the thinner backplane exhibits better thermomechanical performance and is 0.32 kg/m² lighter.