A Unified Framework and Synergy Performance Index for Integrated Energy–Water–Ventilation Systems in Buildings: A Systematic Review

Integrated management of energy, water, and ventilation (E–W–V) systems is increasingly recognised as a critical pathway for advancing sustainable development by reducing environmental impacts, improving resource efficiency, and strengthening climate resilience in the built environment. Despite growing interest, existing research remains fragmented, with limited attention to cross-domain synergies and a lack of standardised approaches for evaluating integrated system performance. This study addresses these gaps by introducing the Unified E–W–V Integration Framework (UEVIF) and the Synergy Performance Index (SPI), which together constitute the first combined methodological tools for systematically characterising and assessing multi-domain E–W–V interactions in buildings. A PRISMA-based systematic review of 107 peer-reviewed studies published between 2015 and 2025 was conducted to identify dominant integration typologies, resource-flow interdependencies, enabling technologies, and reported performance outcomes. The proposed SPI provides a normalised metric for evaluating synergy effects across energy demand, water use, and indoor environmental performance, enabling consistent cross-study comparison and benchmarking. The reviewed evidence indicates that integrated E–W–V strategies can achieve energy-use reductions of 30–70%, water-consumption savings of 20–40%, and measurable improvements in indoor air quality across diverse building types and climatic contexts. Nevertheless, the analysis reveals persistent limitations related to empirical validation, cross-domain modelling, and the absence of unified performance metrics. By offering a transferable analytical framework and a standardised synergy indicator, this review supports evidence-based design, research, and policy interventions aimed at accelerating the transition toward climate-aligned, net-zero, and circular built environments.