The passive cooling effect of window gardens on buildings: A case study in the subtropical climate

Abstract

Previous studies have shown that building greenery systems could provide passive cooling for buildings. However, window gardens, a type of building greenery system that extends along the width of the building façade, have received little attention. In this study, a field experiment of building-integrated window gardens was conducted in Xiamen, a subtropical city in China. The passive cooling effect of window gardens during a daytime in summer was analyzed based on the measured data. The results showed that the local time-averaged surface temperature at the windowpane shaded by plant canopy was 1.1 °C lower than that was not shaded. This local temperature at the bottom wall can be 2.6 °C lower than the time-averaged indoor air temperature. The heat was transferred from the interior space to the window-garden-adjacent envelope with a time-averaged heat flux of 6.9 W·m−2. The variation in the passive cooling effect of the window garden along the vertical direction was quantified. The cooling performance of the window garden was found to be significantly affected by the irrigation system. A strategy to maximize the cooling effect by implementing a soil temperature sensor to control the smart drip irrigation system was proposed, which can be further investigated in the future. Given that window gardens can provide aesthetical and thermal benefits, there is a great potential for the practical use of window gardens for buildings in subtropical climate regions.