The purpose of this investigation is the experimental characterization of the hygric and thermal properties of four clay/vegetable aggregates mixtures. In order to evaluate the hygrothermal behavior of these biocomposites based on different aggregates, moisture buffer value, sorption/desorption isotherm and thermal conductivity were investigated here. This work is carried out in the framework of the BIOCOMP project which aims to develop those locally produced biocomposites to be used as building's interior insulating plasters. This, to offer refurbishment solutions for vernacular buildings in Touraine, Center of France. Sunflower stem and rape straw are considered as agricultural byproducts aggregates whereas local clay is used as binder. In this study, the samples were prepared with the following vegetables: rape straw, sunflower bark, sunflower pith and a mix of sunflower pith and bark. For a same binder:aggregates and water;binder weight ratio, we obtained samples with different densities and different properties depending on the aggregates. The hygric and thermal performances of those mixtures make them competitive in comparison to hemp-lime concrete and could therefore offer a wider variety of refurbishment solutions having a low embodied energy.