Study on the Indoor Thermal Environment of Prefabricated Railway Buildings in High-Altitude Cold Regions for Sustainable Development

Prefabricated buildings offer high industrialization, construction efficiency, and sustainability benefits, making them particularly well suited for adverse construction conditions. As railway networks expand into western China’s high-altitude regions, prefabricated structures have been increasingly adopted for living quarters along railway lines in cold, high-altitude areas. This study proposes a method that accounts for thermal-bridge effects by using the average thermal transmittance coefficient Km and the linear thermal transmittance ψ calculated via two-dimensional steady-state simulations with PTemp software. The approach was validated against 48 h field measurements from a prefabricated building in Weinan: the model incorporating thermal bridges reduced the mean temperature error from 15.6% to 7.74%, confirming its accuracy. Using DeST software, the indoor thermal environment of a railway living-quarter building in the Ganzi region was simulated. Results show that south-facing rooms have an average temperature 2.3 °C higher than north-facing rooms and a 17.74% lower annual discomfort time. Building orientation, south-facing window-to-wall ratio, and envelope thermal transmittance significantly affect overall indoor temperature and energy consumption. The optimal orientation range is 15–45° west of south, and the least favorable range is 135–165°. A south-facing WWR of 0.35–0.45 and an exterior wall insulation thickness of 60–120 mm are recommended. For the typical high-altitude locations Litang, Batang, Qamdo, Nyingchi, Lhasa, and Ganzi, region-specific optimal parameters are provided: exterior wall Km values range from 0.10 to 0.65 W/(m2·K) and window K values from 1.0 to 3.0 W/(m2·K), depending on the local solar radiation and altitude. These findings offer quantitative design guidance for improving indoor thermal comfort and reducing energy use in prefabricated railway buildings on the western Sichuan and Tibetan plateaus.