The study examines the rapidly emerging precast concrete construction as an alternative building envelope technique for mass housing in India’s composite climate. Optimum envelope design enhances occupant comfort while reducing heat risk, energy consumption, and carbon emissions. The study compares seven building envelope configurations for integrated precast concrete construction, including conventional (base case), insulated variants, varied wall thicknesses, energy code-compliant (ECBC-R), and Passive House-compliant design, using a simulation-based approach. A building performance model of a typical multifamily affordable housing was developed with natural ventilation as the primary cooling strategy. The thermal performance of different envelope configurations was evaluated in terms of summer and winter discomfort degree hours and cooling/heating loads. Key findings indicate that increasing the thickness of concrete walls or roofs beyond 150 mm does not provide any significant benefit in reducing thermal discomfort. However, providing higher insulation thickness significantly reduces discomfort degree hours and energy consumption. External insulation is more effective in summer, while internal insulation slightly enhances winter comfort. However, insulation beyond 100 mm diminishes returns in thermal comfort and energy savings but significantly increases embodied carbon. The ECBC-R, minimum performance standard for building envelopes for naturally ventilated residential buildings in India, emerges as the most balanced approach, optimizing thermal performance, energy efficiency, and embodied carbon emissions. The study highlights the need for enhanced environment-friendly insulation strategies, real-world validation, adaptive thermal comfort models, and life cycle assessment.