The Buildings & Construction sector is responsible for more than one-third of the Energy Consumption in India, of which building operational energy is a large contributor. The Bureau of Energy Efficiency (BEE) in India, predicts that 40% of the total building stock that will exist at the end of two decades from now, is yet to be built, which means India will witness an unprecedented construction boom leading to further increase in energy demand in this sector. To contain Greenhouse Gas (GHG) emissions and reduce the carbon footprint of buildings, both new and existing, sustainable design strategies and technologies must be applied. This paper highlights the performance and status of countries worldwide to fight climate change, where India stands - on its path to achieving net zero targets. It also reviews key aspects of building sustainability in existing and new buildings, and energy saving potential of old and new construction. Energy Conservation Measures are simulated using computer models for Building Performance Assessment - a case study of a LEED India Gold-rated building in Chennai is presented.