Sustainable Solutions for Reduced Water Use in Solna Stad - A multi-dimensional assessment of water-saving technologies in multi-family buildings

Abstract

Reducing potable water demand in multi-family buildings is an increasingly relevant measure for municipalities facing growing demand and capacity limitations in water supply infrastructure. This study assessed building-level water-saving technologies in Solna, Sweden, with focus on municipally owned multi-family housing and the mu nicipality’s ability to support implementation. Water-efficient technology, rainwater harvesting systems (RHS), and graywater recycling systems (GWRS) were evaluated across retrofit, planned renovation and new construction scenarios. A reference build ing representing the local municipal housing stock was used to quantify water sav ings, energy savings, climate impact and life cycle cost. The assessment used a mixed methods approach including literature review, semi-structured interviews, quantitative calculations, life cycle assessment (LCA), life cycle cost assessment (LCCA) and multi criteria decision analysis (MCDA). The criteria weights used in the MCDA should be interpreted as illustrative for decision-support rather than a robust stakeholder consen sus. Water-efficient technologies were estimated to provide the highest potential water and energy savings and the lowest costs and climate impacts across all scenarios. The GWRS showed potential for substantial water and energy savings when combined with heat recovery, but was found to mainly be suitable for new construction or major ren ovations due to higher cost and technical complexity associated with retrofitting. The RHS showed limited water-saving potential in the selected reference building configu ration, but may be relevant in other building configurations or where it can also support stormwater management. The municipal assessment showed that Solna has limited authority to require specific building-level technologies but can indirectly support im plementation through stormwater-related requirements, land allocation processes, guid ance, knowledge sharing and collaborative pilot projects. The study concludes that potable water demand in Solna can be reduced using water-saving technology, but that implementation likely needs to follow a gradual pathway combining short-term fixture replacement with long-term knowledge-building around more complex reuse systems.