Optimizing Thermal Comfort and Life Cycle Cost in High-Altitude Rural Housing Using NSGA-II and EnergyPlus

Improving indoor thermal comfort in high-altitude rural housing remains a persistent challenge for low-income communities in the Peruvian Andes. This study evaluates the thermal performance of a standardized Sumaq Wasi modular dwelling in Langui (Cusco, Peru, 3969 m.a.s.l.) and proposes passive envelope modifications that enhance comfort while preserving economic feasibility. A multi-objective optimization approach combining EnergyPlus simulations with the NSGA-II algorithm was applied to minimize total thermal discomfort (TDItotal), bedroom underheating (TDIUbedrooms), and 10-year life cycle costs (LCC). The calibrated model incorporated field measurements of indoor air temperatures. Global sensitivity analysis using Morris and Sobol methods identified ceiling thermal transmittance as the dominant contributor for TDItotal, and exterior wall solar absorptance as the driver of TDIUbedrooms. Optimization reduced TDItotal and TDIUbedrooms to 22% and 8% of the base case, requiring additional investments of USD 2,347 and USD 1,959, above the base case cost (USD 8,100), respectively. Cost-neutral strategies, raising exterior wall solar absorptance to 0.9 and increasing the skylight to roof ratio (13.1%), reduced bedroom underheating to 30% of the base case and outperformed a scenario with two 400W electric heaters. These results demonstrate that context-appropriate passive design can substantially improve comfort under severe climatic and financial constraints.