Seasonal thermal performance of double and triple glazed windows with effects of window opening area

Despite significant advancements in building technologies, a critical gap exists in understanding how Solar Heat Gain and the Cooling Effect of Ventilation (CEV) interact in high-rise residential buildings. These two factors, which are crucial for achieving thermal comfort, operate in opposing directions: Solar Heat Gain leads to heat retention and an increase in indoor temperature, while CEV promotes cooling and reduces indoor temperature. This contradiction creates a complex thermal dynamic that is not well-understood, particularly in the context of high-rise bedrooms with varying window configurations. This study addresses this gap by investigating the seasonal interplay between Window Opening Area (WOA), Solar Heat Gain, and CEV, explicitly focusing on their seasonal variability and the impact of different glazing configurations (double- and triple-glazed windows). This research is conducted in Dongguan, China, and employs field measurements from seven high-rise bedrooms in winter and summer. The study uses advanced instruments such as pyranometers and anemometers to capture precise data on solar radiation, indoor temperature, and airflow, enabling a detailed analysis of the thermal effects of WOA and glazing configurations. The results reveal distinct seasonal behaviours of Solar Heat Gain and CEV. Solar Heat Gain dominates in winter, with heat retention critical for indoor comfort. Smaller WOAs enhance net heat gain, especially in triple-glazed configurations, where Solar Heat Gain values for a 0.32 m2 WOA reached 281-387 W, yielding a positive Net Thermal Effect of up to + 204 W. Conversely, larger WOAs during winter facilitated minimal cooling through ventilation, reducing Net thermal effect and compromising warmth. In summer, the emphasis shifts to ventilation cooling, with CEV becoming the primary driver of thermal comfort. For a fully open WOA (1.3 m2), double-glazed rooms demonstrated significant cooling, with CEV values reaching 1327 W, resulting in negative Net thermal effect values of - 41 to - 60 W. Triple glazing, while reducing Solar Heat Gain to 1001 W offered less effective natural cooling, with CEV peaking at 1179 W. Regression analysis underscores the strong positive correlation between WOA, Solar Heat Gain, and CEV, with double-glazed systems exhibiting higher sensitivity to WOA changes. The Net thermal effect analysis highlights the necessity of adjusting WOAs seasonally-smaller openings in winter maximise heat retention, while larger openings in summer optimise ventilation cooling. This study bridges critical knowledge gaps in thermal comfort optimisation for high-rise residential buildings, emphasising the dynamic balance required between glazing types and seasonal WOA adjustments. The findings provide actionable insights for architects and engineers, supporting adaptive design strategies that balance solar heat gain and ventilation cooling, aligning with sustainability goals and energy-efficient urban living.