The HVAC system is an integral part of the buildings. The maximum power consumption is also caused by the same. For energy-efficient buildings, the energy-efficient HVAC system is a must. This semester we learn about how to design an energy-efficient HVAC system. It starts with basics, working of HVAC, components and specifications of HVAC, typologies of HVAC etc. Designing the system and calculating the cooling load. Also, learn about reducing cooling load by providing active and passive strategies. At last, looking for efficient components and working of a system according to part loads to reduce power consumption and maintain thermal comfort.