A comparative analysis of façades with cool coatings and living green walls in hot-dry climates

Abstract

As cities face climate change and urbanization challenges, cool façade systems like advanced coating materials and living green walls (LGWs) have become popular because of their potential to improve urban sustainability and the thermal performance of existing buildings. The cool facade systems aim to mitigate the urban heat island effect by reducing heat absorption, enhancing occupant thermal comfort, and decreasing building energy consumption by lowering interior surface temperatures. This study compares advanced cool coatings, high-retroreflective materials (HRR), and LGWs regarding thermal performance, energy savings, and carbon emissions for a typical residential building in a hot-dry climate. Scenario-based simulation and optimization methods are combined with comparative analysis to evaluate building performance. Thirty-two façade design options were determined, defining four scenarios (two options with cool coatings and two with LGWs on a façade with brick and stone) for simulation using DesignBuilder software and a genetic algorithm (NSGA-II) optimization tool. The results identified the most optimal façade design option for each scenario. The findings revealed that applying advanced materials lowers the exterior surface temperatures up to 2.5 and 2.15 °C in HRR and LGW facades, respectively. The advanced coating achieved the best performance, reducing total thermal loads by 12.8 %, while the maximum thermal load reduction would be 9.4 % in LGW scenarios. However, considering carbon emissions, the reduction equals 19 and 11.28 % in LGW and advanced coating scenarios, respectively. Moreover, the results showed that LGW options with an air gap layer have better thermal and energy performance than those without an air gap.