This chapter investigates moisture-related risks in lightweight emergency buildings, focusing on the HOMEDONE modular construction system. Starting from experimental observations of surface condensation under real operating conditions, a detailed hygrothermal assessment was performed through numerical simulations. Simulations were extended across multiple climatic contexts and included the evaluation of surface condensation, mold growth risk, and the influence of material properties such as temperature-dependent thermal conductivity. Furthermore, the potential of passive mitigation strategies based on moisture-buffering (MB) internal layers—namely, cementitious render and gypsum plasterboard—was assessed. Results confirmed that both surface condensation and mold growth may represent critical issues in lightweight shelters, even in warm climates, and that appropriate MB layers can effectively reduce or eliminate these risks, with the choice of material depending on climate severity.