Affordable and Sustainable Housing: A Systematic Review of Global Evidence, Equity Gaps, and Policy Pathways

Background The worldwide issue of affordable accommodation has become significant, with more than one billion individuals residing in substandard conditions. The United Nations Sustainable Development Goal 11 (Sustainable Cities and Communities) cannot be achieved without the integration of affordability and sustainability. Nevertheless, the development of cohesive evidence-based housing initiatives is made difficult by the division of current research across technical, social, economic, and governance dimensions. Methods This systematic review was conducted in accordance with the principles of PRISMA 2020 and was registered with PROSPERO (CRD42023458912). Peer-reviewed articles published from 2019 to 2023 were obtained from Scopus, Web of Science, Embase, and MEDLINE in accordance with the PECO framework. A total of 326 recordings were assessed, resulting in 29 studies that met the criteria. The data were synthesized using theme narrative analysis to examine five aspects of sustainability: environmental, building performance, urban/regional planning, governance, and affordability. Meta-analytical tools were employed when methodological consistency allowed. Results Research has shown that sustainable housing measures, such as energy efficiency renovations, life-cycle cost analyses, and circular construction, can reduce thermal energy consumption by up to 35% and provide long-term cost reductions. The benefit-cost ratios are an average of 1.42 (95% CI: 1.11–1.79). However, the data suggest that there is substantial variation among regions (I² = 52–68%). High-income contexts demonstrate cross-sectoral policy integration, whereas low- and middle-income countries continue to experience governance fragmentation, financial limitations, and unequal access. There are still substantial disagreements regarding the effectiveness of central management in comparison to community-led administration, the viability of circular building in the Global South, and the decision between renovating and new construction. Discussion This research demonstrates that sustainability and affordability are not mutually exclusive concepts, but rather mutually supportive when integrated into effective governance, policy, and finance systems. However, there are still shortcomings in the areas of unofficial housing frameworks, equity, and social consequences such as health and unity in communities. The necessity for additional empirical research in the Global South is underscored by the high level of research from affluent regions. Conclusions Adaptable, context-aware techniques that combine life-cycle cost reductions with social integration and environmental effectiveness are required for sustainable affordable housing. To mitigate equity gaps and ensure that housing aligns with climate and biodiversity goals, future studies must prioritize the incorporation of the informal economy, longitudinal policy assessment, and innovative finance.