This study investigates the performance of green roofs with three different types of substrate, which are topsoil, a mix of 60% topsoil and 40% biochar, and a mix of 60% topsoil and 40% cocopeat in terms of saturated bulk density and water retention efficiency with a roof slope of 16.7 degrees. The substrate has a thickness of 35 mm and was supported by a timber green roof prototype with Zoysia Japonica, Local cow grass and 9 o'clock flower as vegetation. It was also observed from the experiment that with respect to vegetation, the water retention efficiency is 50.3% (Zoysia Japonica), 49.3% (Local cow grass), and 57.4% (9 o'clock flower) with topsoil and cocopeat for a rainfall of 10 mm for a period of 20 min. Based on this research, a 9 o'clock flower with substrate combining topsoil and coco peat is recommended for green roofs in tropical climates.
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