Life-cycle Cost Analysis of Using Rainwater Harvesting Systems in Hong Kong Residential Buildings

Abstract

This paper investigates whether the use of Rainwater Harvesting Systems (RWHSs) to provide water for washingmachines in Hong Kong residential buildings would be financially attractive. In such systems, rainwater is accumulatedand reused for doing laundry, garden irrigation, flushing toilets, and even drinking. Thus, the analysis of RWHSs’financial feasibility is essential for construction projects. RainCycle is used to validate financial feasibility, consideringparticular circumstances and data relevant to the Hong Kong context. A range of different scenarios by adjusting threefactors are evaluated: catchment area, water demand, and discount rate. It is suggested that 2,000 m2 would be a suitablecatchment area in a typical Hong Kong residential building and it is demonstrated how water demand and discount rateinfluence the financial performance of RWHSs. In particular, the financial performance of RWHSs is sensitive todiscount rates. The results suggest that the RWH system would be worthwhile for buildings with a lower number offloors, but would barely achieve financial validation in Hong Kong’s super high-rise residential buildings.