In view of the climate emergency and the need for energy transition, the use of materials with low environmental impact based on plant co-products or from recycling is strongly encouraged. Biobased materials have been developed in recent years and have shown interesting performances, particularly for the thermal insulation of buildings. Nevertheless, their use is still hampered by the lack of rules for their use and control of their behaviour in normal or accidental conditions of use such as excess water or fire. In this work, the behaviour of biocomposites based on cereal straw exposed to high temperatures was studied. The objective is to evaluate the effect of this temperature increase on the mechanical strength of the material and its thermal properties using different heating scenarios. The biocomposites considered for this study were developed as part of the PEPITE project funded by the "Region Centre Val de Loire". They are materials composed of two different binders: lime, and plaster, straw aggregates and additives (air entraining agent, casein protein and biopolymer). In order to simulate fire, two temperatures were chosen for the study 200°C and 210°C, using four different heating rates to study their impact on the behaviour of dry and wet conditions of biocomposites. The purpose of this tests is to examine whether the material retains its insulating properties and its buildability. The results showed that the use of additives had negative effects on the behaviour of the materials with respect to temperature increase. Their use accelerates the degradation and burning of biocomposites faster than for samples without additives. Plaster based composites show a better behavior to high temperature than lime-based composites. Nevertheless, lime composites have a higher strength than plasters. Furthermore, the thermal conductivity of plaster is lower than that of lime. It should be noted that the heating rate has a significant impact on the behaviour of the material, the slower the rate, the more the material is degraded.