Due to its inherent large thermal inertia, concrete core activation (CCA) could assist in active demand response schemes. By shifting the injection or extraction of thermal power in time, demand peaks that normally occur more or less simultaneously in clusters of buildings can be spread out in time. Furthermore, thanks to the low temperature differences allowed with respect to the room temperature, CCA is ideally combined with technologies that have increasing renewable potential, such as heat pumps, low temperature district heating and high temperature district cooling. This paper illustrates the flexibility potential of concrete core activation through the exploitation of its thermal energy storage capacity by dynamic simulations. A validated RC thermal model of a CCA is coupled with a detailed building model, including user occupancy and weather disturbances. The flexibility indicator is calculated based on a method presented in the literature, but using an extended version that allows application to more complex systems, including heat losses. Balancing the building between minimal and maximal temperature, the thermal power needed to heat or cool the building can be modulated up- or downward with respect to the reference energy use. The method is applied to various building types with different insulation levels, in order to map the flexibility potential of CCA heating compared to buildings heated with radiators.