A mixed-method systematic review of indoor environmental quality (IEQ) gaps and opportunities for future research
Sunday S. Nunayon, Lexuan Zhong
Abstract
Indoor environmental quality (IEQ) plays a pivotal role in mitigating sick building syndrome and advancing several of the United Nations’ Sustainable Development Goals. Globally recognized as essential for the future of healthy buildings, a comprehensive understanding of IEQ is critical. This study presents a systematic mixed-method review of IEQ research, combining scientometric and qualitative analyses to explore its development, current landscape, and emerging trends. A scientometric analysis of 1200 peer-reviewed articles indexed in Web of Science and Scopus mapped citation patterns and dominant research themes. Findings reveal that while IEQ is a rapidly evolving, multidisciplinary field, most research has focused on occupant health and well-being and energy performance, primarily through the lens of thermal comfort. Emerging areas, such as occupant behaviour, cognitive performance, and cross-domain interactions, are only beginning to gain scholarly attention. Collaborations analysis shows the dominance of the USA and China, with limited contributions from South America and Africa. A qualitative review of 250 selected studies further highlights critical gaps, including small sample sizes, limited exposure-health response data, overdependence on controlled laboratory settings, lack of longitudinal studies, insufficient integration of artificial intelligence for IEQ optimization, and underexplored diversity in health endpoints and study populations. The review also identifies the need to bridge the climate change–IEQ nexus. Together, these findings emphasize the importance of applied, interdisciplinary, and long-term research to better understand and enhance IEQ in real-world contexts. This study offers valuable insights and a forward-looking agenda to guide future research and innovation in the field of IEQ.