Parametric analysis of window frame thermal behavior and energy Savings in hot Climates

In regions with extreme climatic conditions, such as cooling-dominated buildings located in hot climates, window systems remain a critical source of thermal inefficiency, with window frames often exhibiting significantly higher thermal transmittance (U-values) than glazing. Despite their substantial contribution to overall window heat transfer and indoor comfort, window frames remain comparatively underexplored in both research and design practice. This study addresses this gap by conducting a comprehensive parametric analysis of window frame designs to reduce the high U-values associated with conventional aluminum frames. Using a simulation-based methodology integrating THERM, WINDOW, and EnergyPlus, the study systematically evaluates the influence of frame material selection (aluminum, U-PVC, and fiberglass), frame sheet thickness, cavity insulation, thermal break integration, and frame-to-glass ratio on thermal and energy performance. Results indicate that increasing aluminum frame thickness or adding cavity insulation provides negligible thermal improvement. In contrast, replacing aluminum with non-metallic materials such as U-PVC and fiberglass reduces frame U-values from approximately 11.5 W/m²K (baseline aluminum) to as low as 2.4 W/m²K and 2.75 W/m²K, corresponding to reductions of up to 79% and 76%, respectively. While the integration of advanced thermal breaks, particularly a 10 mm aerogel-filled thermal break reduces aluminum frame U-values to approximately 5.0 W/m²K ('50% reduction), while dual-break configurations achieve reductions of up to 67%. Additionally, larger window sizes (≥ 1.7 × 1.7 m) further enhance overall thermal performance by increasing the proportion of lower-U-value glazing relative to the frame. Building energy simulations demonstrate that optimized frame configurations can reduce annual cooling energy consumption by up to 9% in Dhahran and 8% in Abha. These findings highlight the critical role of window frame optimization in improving envelope thermal performance and reducing cooling demand in hot climates. By shifting attention from glazing-centric solutions toward integrated frame design strategies, this study provides actionable insights for designers, material selection, and building energy standards, contributing to more energy-efficient and thermally resilient residential buildings in cooling-dominated regions.