Impact of Retrofitting Building Envelopes on Thermal Performance of Low-Rise Residences in a Composite Climate

Composite climates in North India pose substantial challenges to indoor thermal comfort in existing low-rise residences. This study evaluates the impact of envelope-centric retrofits—cool roofs with roof insulation, external wall insulation, solar-control glazing/shading, and air-sealing—on a detached singlestorey residence in Santkabirnagar, Uttar Pradesh (26.638437° N, 82.940854° E). A mixed-method approach combines post-occupancy IAQ and thermal measurements, occupant surveys, and annual dynamic simulations comparing baseline and retrofitted scenarios, with emphasis on peak summer conditions (May–July). Results indicate peak indoor operative temperature reductions of approximately 2.0–3.5 °C, 30–45% fewer discomfort degree-hours across peak summer months, and 18–30% lower simulated cooling energy demand, contingent on operation and schedules. The paper proposes a prioritized, cost-effective retrofit roadmap tailored for India’s composite climate and discusses maintenance and scalability considerations