The facades of the BIPV building in hot-humid climates are exposed to considerable losses in performance caused by the elevated temperatures and the buildup of soiling. Under these conditions, this paper proposes a transparent, open-source, scenario-based workflow to assess the effect of nanocoating technologies upon the energy performance of BIPV facades in such conditions. The simulation framework is based on PVlib, with a transposition of irradiance via the Perez model, which is a simplified model of temperature correction and a comparative soiling-cleaning model. This method is not designed to predict the performance of a particular facade in detail, but to enable a consistent comparison of coated and uncoated facade situations at an early stage of energy assessment. A case study is done of a south-facing vertical facade in the city of Dhahran in Saudi Arabia. Findings show a rise in the annual energy yield of 264 to 284 kWh/m2/year which is an improvement by 7.62% with nanocoating. The results indicate that the main factors contributing to the increase in performance are the decrease in thermal stress and the decrease in soiling losses. To manage model uncertainty, the parameters are chosen within literature-informed ranges, and results are reported as scenario-based estimates. The offered workflow offers a practical decision-support tool in assessing the BIPV facade strategies in the harsh climate and makes informed decisions in design and operation.