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

Abstract

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.