One-year performance assessment of a passive house container-based prototype: Indoor comfort and energy use

• Nearly zero-energy prototype built from 20-ft shipping containers. • One-year performance evaluation at Zaragoza military base. • High thermal comfort and indoor air quality verified through monitoring. • Heating and cooling energy consumption reduced by 87 % vs. baseline. • Severe summer heatwaves exposed cooling and overheating limitations. This study provides new insights into the energy and environmental performance of buildings constructed from shipping containers, which are widely used worldwide for temporary accommodation in both civilian and military contexts. Such structures often exhibit poor thermal performance and inadequate indoor air quality, as they are typically designed for short-term use despite being occupied for extended periods in refugee camps or military peacekeeping missions. This mismatch between design assumptions and real use leads to suboptimal comfort, high energy demand, and increased operational costs. This research presents a passive, modular, habitable and demountable prototype specifically designed for deployment in Antarctica and adaptable to remote military bases elsewhere. The prototype was developed in accordance with the Passivhaus standard, NATO environmental protection requirements, and the Protocol on Environmental Protection to the Antarctic Treaty. Before its installation at an Antarctica research station, the module was monitored over one year at a military base in Zaragoza, Spain. Indoor environmental conditions (air temperature, relative humidity, and CO 2 ) and energy consumption for ventilation and air conditioning were assessed. Results show that the prototype maintained stable indoor temperatures during winter, avoiding cold-wall and vertical stratification effects, while CO 2 concentrations confirmed consistently adequate air renovation. In summer, acceptable indoor conditions were maintained on most days, although significant overheating occurred during two heatwaves. Overall, the annual energy consumption for heating and cooling was 33.9 kWh/m 2 , representing an 87 % reduction compared with conventional containerised units previously monitored by the authors.