 The European Union's energy and climate policy sets quantitative targets for decarbonization based on the evolution of energy systems and the utilization of demand-side flexibility. Thermal flexibility in a Greek office building was assessed using simulation models, focusing primarily on the storage of thermal energy in the form of thermal mass. Demand response potential was evaluated under various scenarios, including hourly CO2EQ intensity signals and spot price signals. The results showed that both control strategies based on CO2EQ intensity and spot price signals had the potential to reduce energy consumption, operational costs, and CO2EQ emissions, as well as improve thermal comfort. In some cases, however, the potential exists for increased energy consumption and degradation of environmental performance when demand response strategies are implemented. This article was authored by Giorgio's Chancis, Ephraissini-Giama, and Agus M. Papadopoulos. We are article.tv, links in the description below.