Energy positive curtain wall configurations for a cold climate using the Analysis of Variance (ANOVA) approach
Curtain walls are believed to be “energy sinks” because of their relatively low thermal performance; however, the integration of energy generating technologies such as photovoltaic (PV) panels may enable converting these systems to “energy positive” curtain walls. A methodology using the Analysis of Variance (ANOVA) approach is developed and implemented to identify configurations of energy positive curtain walls by accounting for the complex interacting effect of facade design parameters. The “energy positive” curtain wall in this paper is defined as the energy generated by the curtain wall facade on an annual basis exceeds the energy consumption of a perimeter zone office enclosed by this curtain wall facade. Ten design parameters are studied, including glazing U-value, solar heat gain coefficient (SHGC), and visible transmittance (Tv); U-value of the spandrel panel; U-value of the mullion; window wall ratio (WWR); infiltration rate; depth and inclination of overhang; and efficiency of PV modules. The significance of individual design parameters on the energy performance is ranked for four cardinal orientations based on the total sensitivity index. The WWR, U-glazing, and infiltration rate are the three most significant parameters influencing the total annual energy consumption of the office unit simulated, while the WWR, PV efficiency, and U-glazing are the most significant design parameters for achieving energy positive curtain walls. The methodology presented in this paper helps facilitate the design process to resolve the issues with conflicting effects of design parameters.