Green Technology & Innovation, cilt.2, sa.1, ss.225-247, 2026 (Hakemli Dergi)
Heating, ventilation, and air-conditioning (HVAC) systems play a decisive role in the energy consumption, indoor environmental quality, and carbon footprint of contemporary buildings. Despite significant advances in high-efficiency equipment and control technologies, a persistent gap remains between nominal efficiency ratings and realised in-use performance. This discrepancy is primarily driven by dynamic operating conditions, part-load behaviour, climatic variability, and cross-layer misalignment between system design, operational control, and environmental demands. This review adopts a system-level perspective to examine how HVAC performance is shaped through the coupling of design configuration, equipment modulation capability, supervisory control architecture, and sensible-latent load interaction. Rather than treating system typologies, control strategies, and performance metrics as isolated domains, the study organises existing literature within a structured design-operation-performance coupling framework. Centralised, decentralised, and hybrid HVAC configurations are critically reviewed with particular emphasis on part-load thermodynamics, ventilation-humidity interaction, and control coordination under real building conditions. The analysis reveals thatnominal efficiency indicators such as the coefficient of performance (COP) and seasonal ratings represent equipment potential rather than guaranteed operational outcomes. Performance degradation commonly emerges from conservative sizing practices, limitedturndown capability, inadequate supervisory coordination, and humidity-dominated operating regimes, especially in ventilated and humid climates. The review further highlights that effective performance realisation depends less on individual component efficiency and more on the coherence between system architecture, modulation strategy, and control hierarchy. By synthesising experimental findings, field studies, and simulation-based research, this work provides an integrated evaluation logic for interpreting HVAC efficiency beyond static ratings. The proposed framework supports more reliable performance assessment, informs design and commissioning practices, and contributes to narrowing the persistent gap between predicted and realised HVAC performance in contemporary low-carbon buildings.