Revealing the gaps in multi-domain comfort control: A relationship-graph approach based on a systematic review

Multi-domain indoor environmental quality (IEQ) control has emerged as a promising approach for balancing occupant comfort and building energy use (BEU). However, the absence of a clear conceptual structure for defining and evaluating such systems has led to inconsistent formulations and limited comparability across studies. This study examines existing approaches and assesses their alignment with a newly developed conceptual structure for multi-domain control. A systematic review was conducted using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology guided by the CIMO (Context-Intervention-Mechanism-Outcome) logic. An initial identification of 972 studies addressing control strategies across multiple IEQ domains and BEU was identified, from which 125 studies were retained following screening and eligibility assessment. The analysis shows that only 15 studies explicitly integrate more than one IEQ domain with BEU within a control system formulation. All retained studies incorporate energy use and thermal comfort, while indoor air quality (IAQ) appears in one study, visual comfort in two, and acoustic comfort in none. Across these studies, comfort is frequently reduced to single environmental variables and governed through fixed setpoints, with indoor environmental conditions treated as direct proxies for occupant comfort. A relationship graph is introduced to interpret these patterns and reveals structural limitations, including the omission of cross-domain interactions, the absence of an intermediate IEQ layer linking environmental conditions to perceived comfort, and the selective treatment of contextual drivers due to computational and uncertainty-related constraints. These findings indicate that most existing approaches function as autonomous rather than occupant-centric control systems.