Passive Cooling Retrofit Strategies for Reducing Energy Demand in a Residential Building in Karachi, Pakistan

Buildings are the biggest electricity consumers and carbon emitters, and space cooling and heating are responsible for a substantial amount of the energy usage. In developing nations, the energy efficiency of existing residential buildings is often poor owing to poor thermal design and the prevalence of energy-intensive cooling systems, which provide immense potential for improvement through retrofitting. This paper describes an Autodesk Ecotect based retrofit analysis of a residential building in Karachi, Pakistan, using passive cooling systems as a case study. A reference building model was created and analyzed from 1 January 2025 to 31 December 2025 to determine the annual heating and cooling demand, solar access, passive heat gain terms, ventilation-related gains, and indoor air temperature. Various retrofitting options were explored, such as argon gas-filled double glazing with solar control film, improved natural ventilation with wind catcher and cross ventilation, green roofs, insulation of building envelopes, exterior reflective coatings with different reflectance values, and indirect nocturnal radiant cooling. The analysis indicates that substitution of single glazing with tinted double glazing resulted in a 12.17% reduction in annual thermal loads with improved indoor comfort conditions. In addition, energy retrofits at the appliance level, using efficient lighting and appliances, decreased the monthly electricity consumption from 539 kWh to 390 kWh, resulting in a monthly savings of 149 kWh. The results show that combining passive envelope and ventilation retrofits with efficient appliances can be an effective way to reduce cooling-driven energy demand and improve thermal comfort in residential buildings in hot climates.