orientation. To facilitate the growth of photovoltaic utilization, forecasting solar irradiance using simulation tools has become an effective predictive measure to forecast photovoltaic power generation. However, the prediction accuracy in the simulation tool needs to be verified through the validation process. This experiment was performed in the field test and the calculated data from this measurement was used to verify the data from the simulation. Based on the recommended validation measures, this study examines the errors and precision of the forecast model in the simulation system. This field experiment covers eight different vertical façade configurations. The result indicates that the vertical façade to the east and west exposed the most incident radiation.