In the framework of the European Green Deal, launched at the end of 2019 by the EU Commission, all buildings in operation should be virtually climate-neutral by 2050. To achieve this goal, innovative energy concepts are urgently needed in the field of construction and building applications. The increased interest on advanced building technologies, novel construction techniques and high-performance insulation systems, in combination with intelligent energy storage materials, both in new buildings and/or in renovation ones, could significantly increase the potential for reducing energy consumption for heating and cooling. The heat storage capacity of building materials plays a key role in this context. Through an intelligent combination of embedding phase change materials (PCMs) in classical building materials, a large amount of thermal energy can be stored, even within low temperature differences and/or jumps. Up to now, there is no standardized model for describing the effective heat storage capacity and no dynamic measuring method is available for determining the heat storage capacity of a heterogeneous cementitious composite with PCMs. Accordingly, a macroscopic model approach based on homogenized thermal properties of a composite material is presented and proven to be functional. After the experimental determination of the heat storage capacity of individual components, according to standardised measuring procedures, the effective heat storage capacity can be determined according to the most general mixed-theory. Moreover, an adapted calorimetric method, built up from spherical specimens/shapes, has been developed to validate the model approach. The latter, named "Dynamische Kugelkalorimetrie" (DKK method), uses radial symmetry of a spherically shaped volume. With the help of the DKK method and the underlying hypothesis, an inverse numerical determination of the effective heat storage capacity was carried out. In the final comparison between the model approach based on the effective heat storage capacity and the newly developed indirect measuring method for the dynamic determination of the temperature-dependent effective heat storage capacity of heterogeneous PCM composites, the maximum deviation is less than a few percent.