Indoor dwelling habitability: conceptual evolution, methods, and key variables from a systematic review

Indoor dwelling habitability is increasingly recognized as a determinant of health, comfort, and housing performance; however, its assessment remains conceptually fragmented and methodologically heterogeneous. This study presents 97 scientific contributions identified through a PRISMA 2020-guided process: 68 from systematic database searches (2016–2025) and 29 from complementary manual search. It clarifies the field's conceptual evolution, methodologies, indices, and variable structures. Results reveal a marked expansion from technical-structural adequacy toward a multidimensional construct that includes health and well-being, reflecting cumulative integration rather than conceptual rupture, with a growth in publications that coincides with the post-COVID-19 period. Regional trajectories vary according to climatic, socio-economic, and regulatory conditions, limiting unified operationalization across contexts. Mixed-methods approaches predominated (47%), reflecting the integration of environmental measurements with occupant perception. Despite methodological diversification, only 18% of the reviewed studies incorporated habitability-related indices, and just 2% proposed indices focused on the dwelling interior. While the review identifies a persistent scarcity of interior-focused assessment frameworks, it also identifies a stable empirical core of indoor habitability variables. A total of 220 variables were identified and harmonized into 52 standardized variables. The 30 most recurrent variables appeared in 94% of the reviewed studies, suggesting a convergence around environmental and functional parameters, particularly lighting, ventilation, humidity, temperature, IAQ, basic services and overcrowding. These results should be read in light of the review's scope, which focused on the habitability and livability terminology and did not include records without full-text access. These findings support the development of dual-structure tools integrating a universal environmental and functional core with context-adaptive components, informing future housing policies, anticipatory building standards, and strategies to mitigate emerging environmental and socio-climatic risks.