Abstract
As climate change leads to increasing temperatures and precipitation, building envelopes must adapt to ensure durability. Meanwhile, improving energy efficiency requires integrating new technologies directly into the building envelope. In this context, building-integrated photovoltaics (BIPV) are increasingly being adopted. However, the hygrothermal performance of BIPV components in cold, humid Nordic climates remains insufficiently characterised. This study develops and validates a computational model of the ventilated roof with BIPV at the Zero Emission Building Laboratory, a full-scale office laboratory in Trondheim, Norway. The model is implemented in COMSOL Multiphysics and simulates coupled heat and moisture transport in the ventilated air cavity, accounting for turbulent airflow, surface-to-surface radiation, moisture transport in air, and heat transfer in both solids and fluids. Boundary conditions are defined through available in situ measurements. Model validation uses temperature and relative humidity data from two sensors located near the inlet and outlet of the air cavity during two representative periods with different climatic conditions. Temperature predictions show CV(RMSE) values of approximately 6–16% and NMBE between -10% and +8%. Relative humidity predictions show CV(RMSE) values of about 8–9% at the inlet and 20–24% at the outlet, with NMBE ranging from -13% to +8%. Pearson correlation coefficients range from 0.85 to 0.99, indicating generally good agreement in the temporal evolution of the variables. The results provide insights into the coupled thermal and moisture behaviour of ventilated BIPV roofs in cold climates and support the design of climate-resilient and energy-efficient building envelopes for Nordic conditions.