In the recent years, the integration of heat storage systems inside building components has been applied for heating and cooling purposes. The implementation of the thermal energy storage inside the building is used to manage and smooth the peak demand. An innovative constructive system including heat storage has been designed to reduce the energy consumption of the HVAC systems, during both heating and cooling periods. It consists of a prefabricated concrete slab with macro-encapsulated PCM inside its hollows. An installation of air ducts allows the air to be forced through the inside of the slab and therefore enhancing the heat exchange with the PCM. The operational mode during summer lies in solidifying the PCM during the night time and using the cold stored as a cooling supply during the day. Moreover, a solar air collector is installed for the winter mode, where the heat from the solar radiation is used to melt the PCM and cover part of the heating demand. The objective of this study is to analyse the benefits of this new system and to quantify its potential in reducing the energy consumed both for heating and cooling. The work partially funded by the Spanish government (ENE2011-28269-C03-01 and ULLE10-4E-1305)