Building sustainability in India is a complex and challenging task, but it is also a pressing need. India is a fast-developing country with a huge and growing population. This fast growth has put a strain on the nation’s natural resources and the environment. The construction and operation of buildings in India have an enormous impact on energy consumption and carbon emissions. Understanding the energy footprint and life cycle cost of these structures is essential for sustainable development and climate action. This study presents case studies of two energy-efficient and affordable residential units in two cities with distinct climatic conditions. The approach used in this study comprises obtaining the bill of quantities (BOQ) and construction material inventory from the designers and contractors of the buildings. The two case studies are analysed for their carbon footprint and life cycle analysis and compared their sustainable performance with the conventional buildings. It is found that Building 1, an independent home constructed with CSEB, in a Temperate climate has over 78% reduction in the carbon footprint with over 50% life cycle cost compared to conventional building; Whereas, Building 2, a multi-family housing constructed using monolithic RC wall, in a Warm and humid climate has over 31% reduction in the carbon footprint and over 33% reduction life cycle cost compared to conventional buildings. In addition, it is observed that although their life cycle costs are comparable, the carbon footprint of Building 2 is over five times higher than Building 1. This is majorly due to the level of mechanisation and the embodied energy of the materials used in the construction. Building 2, a multi-family home, has a development density that is more than three times that of Building 1, an independent, detached home. As analysed and critically observed in this study, it is important to consider the energy, environmental, and economic factors while defining sustainable performance considering the building’s life cycle.