Abstract
The transition to near-zero-energy buildings requires advanced envelopes to mitigate winter thermal losses and the “cold-pane” effect inherent to passive highly glazed façades. This study empirically evaluates an active triple-glazed unit with an integrated flexible heating foil to enhance thermal comfort. A dual-zone climatic chamber simulated severe sub-zero conditions down to −25 °C, utilizing high-resolution thermography, heat-flux sensor arrays, and Fanger’s criteria to quantify conjugate heat transfer and local discomfort. The results indicate that passive operation at −25 °C depresses inner surface temperatures, yielding severe perimeter dissatisfaction (predicted percentage of dissatisfied, PPD > 20%) and restricting the permissible window-to-wall ratio (WWR) to 22.7% to meet Category A comfort standards. Conversely, activating the heating setpoint to 40 °C establishes a near-adiabatic thermal barrier that neutralizes radiant asymmetry, suppresses convective downdraughts, and restores microclimatic stability (PPD < 10%). In conclusion, dynamic electro-thermal modulation effectively eliminates the perimeter cold sink, theoretically permitting up to a 100% WWR ceiling and relaxing the restrictive architectural constraints of conventional passive glazing under extreme winter conditions.