Assessment of thermal performance of energy-active window systems in hot climates

•The study clarifies the impacts of various transparent envelope thermal parameters on glazing surface temperature.•It provides optimum condition design guidelines for EAW in hot climates by investigating the thermal performance of DGEW and TGEW with different parameters.•The study examined EAW’s thermal performance with varying air gaps, air velocity, return air temperature, and pressure values.•The outcomes add another level of validation to the experimental model by using the same CFD simulation to validate the experimental and mathematical models. Window systems, particularly in hot climates, are the source of considerable heat transfer that affects the buildings’ indoor environment and energy consumption. Proper design and optimization of its thermal performance significantly contribute to the overall envelope energy performance. Using a multi-layer glazing system, Energy Active Window (EAW) adapts window insulation technology to reuse low-grade air from the HVAC system, keeping the temperature at the internal surface of the window close to the indoor air temperature, minimizing heat exchange between indoor and outdoor. This study aims to reduce energy consumption by optimizing EAW to increase its thermal resistance by channeling the return air (RA) from the HVAC system into the curtain frame, thereby lowering the temperature of the air gap and air film layer. The study examined the window system’s exhaust/return air behavior using the Computational Fluid Dynamics (CFD) tool (Fluent) to simulate the heat exchange between outdoor and indoor building environments. The CFD simulation was validated using experimental measurements. Results show a surface temperature decrease of 4 to 7 °C based on the inner and outer pane airflow conditions when the outdoor temperature is 45 °C with an 8 % margin of error. Various EAW components were tested, including air velocity, air–gap width, volume, and outdoor temperatures, examining both triple and double-glazing layers.