BSAS Block 1 demonstrates how the building’s original passive design can work alongside modern sustainability measures. Its OTTV of 34 W/m² and roof U-value of 0.49 W/m²K support reduced heat gain, while thick masonry walls, high ceilings, shaded walkways, and natural daylighting provide passive environmental benefits. The project targets a 34% reduction in energy use, achieving a BEI of 138 kWh/m²/year, while water-efficient fittings contribute to a 66% reduction in water consumption. Approximately 60% of the existing building materials are retained and reused, reducing embodied carbon and avoiding the environmental impacts of demolition and reconstruction. Together with low-VOC materials, ozone-friendly refrigerants, and energy-efficient lighting, these measures demonstrate how minimal intervention and adaptive reuse can transform a historic building into a more sustainable asset.