Curtain walls are believed to be “energy sinks” because of their low thermal performance, however, the integration of energy generating technologies such as photovoltaic (PV) panels may enable converting curtain walls to “plus-energy” curtain walls. The “plus-energy” curtain wall is defined as the energy generated by the curtain wall façade exceeds the energy consumption of a perimeter zone office. To design plus-energy curtain walls, design parameters of curtain walls are prioritized by sensitivity analysis and the most critical design parameters corresponding to specific energy efficient measures that bring major energy benefits with minor modifications are identified. 

An office unit with five adiabatic faces and one exterior façade completed with curtain walls is developed as the energy model in EnergyPlus. The indoor environmental parameters are set based on ASHRAE energy standard. 

In this study, global sensitivity analysis is conducted to prioritize the energy impact of ten design parameters, U-value of glazing, solar heat gain coefficient of glazing, visible transmittance of glazing, U-value of spandrel panel, U-value of frame, window wall ratio, infiltration, depth of overhang, inclination of overhang, and effective efficiency of photovoltaic panels. The three most significant design parameters are identified for four orientations. Plus-energy curtain wall configurations at different window-to-wall ratio (WWR) and orientations are identified according to the total sensitivity indices.  The significance of this study is to provide design recommendations of plus-energy curtain wall configurations under different WWRs and orientations, which are not covered in the current design guidelines.