Low-carbon, strategy-driven techno-economic analysis of various passive measures for energy efficiency in a humid subtropical climate: a case study in Pakistan

Pakistan faces critical challenges from global warming and rising energy demand, particularly for space cooling needs. This study evaluates the technical and economic performance of low- to medium-cost passive cooling/heating methods in reducing energy consumption for an educational (university) building in a subtropical climate. EnergyPlus simulations were conducted to assess individual and combined measures. Results show that adjusting temperature setpoints by ±2°C yields the highest savings, reducing cooling energy by 27% and heating energy by 62%. Green walls (GWs) and roofs also demonstrate strong performance, cutting heating demand by up to 42% and 37%, respectively, while short-wave reflectivity (SWR) reduces cooling loads but slightly increases heating demand. Combining measures further enhance performance, with the best-performing combination (C10: setpoint adjustments) achieving ~14% annual savings and C6 (SWR + louvers) reducing cooling energy by ~27%. The building’s energy use intensity is 154.71 kWh/m2/year, which exceeds the benchmarks reported for similar climate countries. Among the measures, temperature setpoint adjustment, requiring no initial investment, proves to be the most cost-effective while GWs/roofs and double glazing, though medium cost, deliver substantial long-term savings. These findings emphasize the potential of practical, scalable passive measures to reduce energy consumption and support sustainable building design in subtropical regions.