Impact of Window-to-Wall Ratio (WWR) and shading on energy demand in a residential building across five distinct climates

Abstract

This study investigates the impact of window-to-wall ratio (WWR), shading strategies, and envelope’s insulation levels (U-value) on the heating and cooling demands of a block of flats across five climate zones near 40° latitude (Ankara, Beijing, New York, Rome and Wellington). The building model was developed in TRNSYS18 and simulated over a full year. Results demonstrate that shading strategy had the greatest influence on total energy demand. Among the three shading types, movable shading consistently achieved the lowest energy demand in south-facing apartments: 10 kWh/m2·yr in Wellington, 45.5 kWh/m2·yr in Ankara, 59.5 kWh/m2·yr in New York, 65.5 kWh/m2·yr in Beijing and Rome 20 kWh/m2·yr all with 60% WWR and a U-value of 0.1 W/m2K. The optimal WWR was found to be 10% for fully north-facing and 60% for fully south-facing apartments when using movable shading and high-performance insulation. Compared to unshaded configurations, movable achieved reductions up to 56% in Rome in south-facing apartments with 60% WWR and a U-value of 0.3 W/m²·K. Moreover, a significant correlation was found between U-values and energy demand in all cities except Rome. These findings underscore the importance of integrating adaptative shading, WWR and insulation strategies into building designs, tailored to climate and orientation, to support energy efficiency and sustainable urban planning. Copyright © 2025. Published by Elsevier B.V.