The impact of urban green infrastructure as a sustainable approach towards tropical micro-climatic changes and human thermal comfort

Abstract

Green infrastructures such as living walls are technological solutions to replace the declined greenery at urbanized environment and also reliable applications for thermal regulation in buildings through insulation effect and escalates the energy use efficiency. Thermal comfort and local climate are spatiotemporally variable. The existing research gap should be addressed by evaluating the performance of vertical green walls in tropical condition. In this study, thermal performance, relative humidity (RH) and CO2 concentration were quantified for basic three types of green infrastructures; such as (T1) living walls, (T2) indirect green façades and (T3) direct green façades located in Colombo metropolitan in Sri Lanka. An in-situ experimental study was conducted considering temperatures at 1 m and 0.1 m distance in front of the green walls, inside the foliage, air gap and external wall surface comparatively to adjacent bare wall control. Three case studies per green infrastructure within Colombo metropolitan area were purposively selected. Simultaneously, RH and CO2 concentration at 0.1 m in front of the green and bare walls were measured for the performance quantification. The internal thermal comfort simulation and occupants’ satisfaction questionnaire survey was executed to assess the green infrastructure performances. The study revealed that vertical greenery systems were highly effective on external wall surface temperature reductions at 1100 h–1500 h time zones. T1 and T2 accounted for superior temperature reduction in the range of 1.61 °C–1.72 °C through the façade relative to the distance than T3. Maximum temperature reduction compared to the bare wall control was obtained for the T1 (0.28 °C–8.0 °C) followed by T2 (1.34 °C–7.86 °C) and T3 (1.34 °C–6.64 °C). Averaged RH increment (1.6%–1.81%) and CO2 reduction (0.63%) occurred near green walls at day time compared to control. An average 28 °C simulated indoor temperature circumstantiate the indoor thermal comfort. 58% and 89.5% occupants’ were satisfied with thermal and visual comfort respectively, thus emphasizing façade greening as a sustainable approach on micro climatic changes and human thermal comfort.