Net-zero water feasibility in a typical house in San José, Costa Rica: a one-water case study

Climate change presents new challenges to urban water infrastructures, and particularly complicates resilient water supply for buildings. Research has focused on carbon emissions consequences of building construction and operation, and structural durability in extreme events, but a gap exists around the potential for buildings to achieve or contribute to climate resilient water systems. Net zero water (NZW) buildings aspire for greater autonomy from centralized supply through both demand management and aggressive use of alternative water sources, thereby ensuring sustainable water supply for occupants. This paper presents a case study of quantitative feasibility of NZW performance using field data collected from a typical Costa Rican house and a water balance simulation model of eight alternative water harvest scenarios. After implementing NZW strategies, wastewater production impact ranges from a 9% increase to a 91% reduction. Required collection tank size ranges from 22 to 64 kL. While water from alternative sources can meet the quantity of water used in the house in in all but one scenario (rainwater harvesting alone), current regulation prohibits implementation in all other scenarios, suggesting the need for regulatory reform of greywater reuse.