A Comparative Analysis of Sustainable Retrofitting Techniques in old Existing Institutional Buildings: Balancing Energy Efficiency, Economic Feasibility, and Environmental Impact

Abstract

The increasing demand for energy effective infrastructure calls for the upgrade of the existing building stock through sustainable retrofitting. Existing buildings often have poor thermal performance, outdated mechanical systems and are disproportionate contributors to greenhouse gas emissions. This study aims at a holistic comparative investigation on passive and active retrofitting techniques in an empirical case study of an institutional building in Pune, India. The baseline energy audit showed an Energy Performance Index (EPI) of 9.36 kWh/m². Simulations were conducted for individual and combined retrofitting strategies of envelope insulation, cool roofs, double glazing, high efficiency HVAC upgrades, and expanded solar photovoltaic (PV) integration. These strategies were evaluated based on energy savings, lifecycle cost, and carbon reduction. Quantitative results show that active upgrades such as HVAC optimization can realize up to 40% isolated energy savings, and holistic approaches that incorporate passive design changes and active retrofits can reach peak reductions of 50-75% in energy consumption, and a 30-50% decrease in operational carbon footprint. Economic indicators show that lighting retrofits have short payback periods (1-3 years), whereas extensive combined measures deliver maximized lifecycle value with an optimized payback period of 5-7 years. This study presents a scalable multi-criteria decision framework to assist stakeholders in choosing optimal retrofit configurations based on structural, economic, and regional climatic variables.