The impact of climate change has prompted government authorities to implement regulations aimed at reducing energy consumption and CO2 emissions. The construction industry holds a prominent position among the major greenhouse gas emitters, contributing a large amount of global energy consumption. A significant portion of these emissions is attributed to heating. In response to these challenges, the use of biobased materials emerges as a solution. In this context, this study aims to assess the impact of low-carbon binders on the mechanical and thermal properties of biobased insulation materials. Binders such as natural prompt cement and natural air lime CAEB CL 90-S are considered sustainable, low-carbon alternatives. The results highlight that hempcrete (cement/hemp) exhibits enhanced mechanical strength with a 0.80 MPa at 28 days and low thermal conductivity with a value of 0.12 W/(m·k). In comparison, hempcrete with lime exhibits lower mechanical strength (0.4 MPa) and thermal conductivity (0.20 W/(m·k)) at 28 days and flax shives with both binders. In a parallel manner, it is observed that the compressive strength of flax shives, when combined with both binders, is inferior to that of cement/hemp. Simultaneously, the thermal conductivity of flax shives with both binders surpasses that of cement/hemp.