‘Flash DSC’ experiments were carried out to validate the Molecular Dynamics models. Unlike conventional DSC, it can reach very high cooling rates, up to 4,000 K/s; extreme conditions under which PHBV remains fully amorphous, allowing for a more precise measurement of its glass transition temperature (Tg). Two methods are compared: one where obstructing structural relaxation effects must be corrected, and one that uses them to identify the glass transition itself. Within the ViSS project, this work is crucial to accurately predict the thermal properties of PHBV and understand how to control its crystallisation.