This lecture explores control strategies in intelligent buildings, from basic on/off and PID control to advanced approaches such as Demand-Controlled Ventilation (DCV), Model Predictive Control (MPC), Reinforcement Learning, and Fault Detection and Diagnostics (FDD). It examines the fundamental energy–comfort trade-off, including thermal comfort models, adaptive comfort, and personalised control. The lecture highlights why the right strategy must match the building’s complexity, operation, and maintenance.