Intelligent net-zero energy buildings: A four-pillar framework and three-axis classification with implementation pathways

Net-zero energy buildings (NZEBs) are a key part of global decarbonization strategies because they are designed to balance building energy use with renewable energy generation. However, their implementation is limited by inconsistent definitions, uncoordinated technology assessments, and the absence of articulated implementation strategies. Prior work often addresses solar photovoltaics, energy storage technologies, efficiency measures, and intelligent energy management systems in isolation rather than as an integrated system, resulting in limited insight into system-level interactions and design implications. This study tackles these gaps using a structured narrative review organized around four interdependent pillars: (i) diversified renewable energy supply, (ii) integration with energy and mobility infrastructure, (iii) comprehensive efficiency measures, and (iv) adaptive intelligent energy management systems (IEMS). We propose a unified three-axis NZEB classification based on (a) energy balance, (b) building grid relationship, and (c) location (ownership) of renewable resources, and, using quantitative evidence and qualitative synthesis, we also develop comparative heuristics to support design and policy decisions. Results indicate that solar-dominant configurations suit residential NZEBs in high-insolation regions; hybrid photovoltaic-wind systems with storage perform well in many commercial applications; and, for industrial sites, smart-grid integration and demand-side flexibility are decisive. Across building types, reliable and cost-effective decarbonization depends on the tight coordination of the four pillars, with advanced digital controls (AI/IoT) enhancing performance. Emerging market mechanisms like blockchain-enabled peer-to-peer energy trading offer additional flexibility and economic optionality. The review concludes with a practical roadmap that enables cross-pillar integration, transparent benchmarking, and actionable guidance for researchers, policymakers, and practitioners.