Selection of tropical plants for an extensive green roof with abilities of thermal performance, energy conservation, and greenhouse gas mitigation

The development of green roofs to mitigate urban heat island effect is critical for conserving energy and reducing carbon footprint. This study evaluated the thermal performance of an extensive green roof design compared with a conventional roof and assessed the suitability of thirty-two plants for low-maintenance green roofs in a tropical area. Experiments were carried out in four phases, covering the tropical climatic conditions from June 2016 to December 2017. The results indicate that a green roof temperature was significantly lower than that of a conventional roof by 12 °C. This led to an 84 % reduction in heat transfer through the building, potentially leading to a decrease in electricity consumption by 0.20 kWh/m2/8 h and saving electricity costs by 0.019 USD/m2/8 h, achieved through a reduction in the cooling load on air conditioners. The highest carbon dioxide removal achieved in this study was 3.01 kgCO2/m2, with an effective mitigation of greenhouse gases by 28.46 kgCO2eq/m2/year. The top three plant species recommended for a low-maintenance green roof are Dracaena cochinchinensis, Santisukia kerrii, and Dracaena kaweesakii. The plant characteristics for low-maintenance green roofs in tropical climates include drought and extreme weather tolerance, disease and insect resistance, short and spreading roots, succulent leaves with ability to store water, low water requirements, slow growth rate, easy availability locally and affordability, thriving in low-nutrient conditions, and a high evapotranspiration rate. In applicable contexts, green roofs designed with suitable tropical plants could potentially enhance urban environments and contribute to achieving low-carbon and environmental sustainability.