This work focuses on the investigation of the hygrothermal performance of four different wall insulation assemblies including starch/beet pulp composite for an office in France under two climatic conditions. Subsequently, a comparative performance analysis is made on all studied assemblies by substituting the Starch/beet pulp composite with hemp concrete (HC). For each design, the overall energy performance, total water content, drying rate and condensation risk were evaluated through hygrothermal simulations using the WUFI® Plus software and mold growth risk assessment was conducted with WUFI®Bio software. Results showed that insulation assemblies based on Starch/Beet pulp exhibited a slightly improved effectiveness in potential energy savings and higher dryness rate while having a higher condensation risk, a lower dynamic thermal performance, and a higher susceptibility to mold growth risk. Moreover, insulation assemblies based on Starch/Beet pulp demonstrated better hygrothermal performance under Nancy’s climate compared to that of Marseille. Wall assemblies based on hemp concrete reduced total energy consumption by up to 35 % in Nancy’s climate and 24.9 % in Marseille’s climate. In comparison, starch/beet pulp concrete achieved reductions of up to 37.5 % and 26 % respectively. However, the mold growth risk for starch/beet pulp was 1.2–7.2 times higher than for hemp concrete. In Marseille’s climate, this risk was 2.3–8.9 times higher for starch/beet pulp and 4.7–17.8 times higher for hemp concrete compared to Nancy’s climate. The findings from these room-scale studies enhance the understanding of the hygrothermal behavior of the Starch/Beet pulp bio-composite material by comparing its performance, under the same conditions, to that of the well-studied hemp concrete material in the literature. Additionally, these studies provide greater insight into the impact of water on the overall energy consumption, service performance of a building and health hazards. Finally, this research also tackles the challenges of integrating innovative materials into the established construction industry.