This lecture explores the Integrated Design Process (IDP) for intelligent buildings, highlighting why building performance is largely determined during the design stage. It examines multidisciplinary collaboration, energy modelling, BIM coordination, BAS integration, performance goals, and design tools such as EnergyPlus, DesignBuilder, IES VE, CFD, and BIM platforms. The lecture emphasises how early collaboration between architects, engineers, technology specialists, sustainability consultants, and facility managers can reduce performance gaps and deliver high-performing intelligent buildings.