Experimental Measurement and Predictive Modelling of Wind-driven Rainwater Collections from Building Facades Towards New Vertical Rainwater Harvesting Systems in Tropical Urban Setting

The vertical expansion of cities has increased the impervious areas by integrating a large portion of tall building curtain wall facades. Wind-driven rain (WDR) load on the facades has amplified urban rainfall runoff. This factor highlights facade areas to be further explored as new catchment areas for vertical rainwater harvesting (VRWH), as well as mitigating their negative impacts on rainfall runoff. This study aims to explore the predictability of WDR load quantity for VRWH on building facades. Due to the lack of in-situ WDR dataset, a one-year in-situ measurement is conducted for predictive modelling of the WDR intensity (Rwdr). WDR coefficients of the semi-empirical models, i.e., the ISO standard 15927–3 (α) and ASHRAE standard 160P (FL), are refined afterwards to improve the predictive performance of the models. The results showed significant improvement; the ISO model predicted annual harvesting Rwdr (mm/h) up to 40.91 mm/h per square metre, equivalent to 29% for potable and 70% for non-potable usage reduction. The ASHRAE model predicted annual harvesting Rwdr (mm/h) up to 63.24 mm/h (per sqm), equivalent to 44% for potable and 109% for non-potable usage reduction, at heights greater than 50 m. Graphical Abstract