The study presents an integrated experimental–numerical analysis of the thermal behaviour and indoor comfort of rapidly deployable pneumatic shelters intended for emergency and military use. Full‑scale climatic chamber measurements were combined with dynamic simulations in DesignBuilder/EnergyPlus to evaluate heat losses, insulation performance and thermal comfort under winter conditions. Model validation confirmed high accuracy, with less than 2% deviation between calculated and measured heat loss coefficients (63.46 W/K vs. 67.62 W/K for the uninsulated tent; 32.79 W/K vs. 33.25 W/K for the insulated tent). Simulations for Kyiv climate demonstrated that adding internal insulation significantly reduces transmission heat losses: at −22 °C total losses decreased from 2.9 kW (uninsulated) to 1.6 kW (insulated). Seasonal calculations showed that a 2 mm insulation layer reduces peak heat losses from approximately 2500 W to 1100 W, while increasing thickness to 5 mm further lowers them to about 800 W. Thermal comfort assessment using the PMV index revealed that uninsulated shelters cannot ensure acceptable conditions at low outdoor temperatures. At −22 °C, PMV reached −1.09 (category IV), whereas insulation improved PMV to −0.50, accompanied by an increase in mean radiant temperature of more than 8–10 °C. The results confirm that even thin insulation layers substantially enhance energy efficiency and occupant comfort. The validated methodology provides a quantitative basis for selecting optimal insulation thickness, improving envelope configuration and defining heating system operation strategies for mobile shelters in cold climates.