Increasingly expensive and polluting sources of energy dictate the need of energy conservation in the society. The major energy consumption contribution in the operation phase of modern buildings is from their HVAC systems. Well planned HVAC systems may provide healthy and comfortable indoor environment, while poor design may result in wastage of energy. Traditionally the design of the systems is based on a constant number of occupants while the situational awareness of the system has been ignored. This paper focuses on the intelligence of the HVAC system in terms of its knowledge of the occupants of the facility in real time. Thermal comfort analysis is applied to study the indoor climate of buildings for efficient use of such HVAC systems. Computational Fluid Dynamics (CFD) is used to model and simulate the indoor conditions. Building Information Modelling (BIM) is used to be a platform to integrate all the data and apply spatial analysis and Green building standards are embedded in the BIM model to evaluate the building sustainability. Based on the results, more reasonable allocation of individual's location in a room can be provided and an automatic control of lighting, air conditioning can be suggested to optimize energy consumption based on matching occupants' comfort level.