Buildings are one of the major consumers of global energy with a significant share reaching to 40%. Phase change materials (PCMs) are used in building materials and structures for energy saving in buildings. PCM absorbs heat from solar energy during daytime and releases that heat when temperatures cool down at night. The benefits of using PCMs in building materials are to reduce peak load and energy demand for heating and cooling and attain smaller temperature fluctuations. The aim of this study is to demonstrate passive utilization of solar energy storage in buildings with a new microencapsulated bio-based PCM (mPCM). The demonstration involves several development steps, which start in the laboratory for development of mPCM suitable for concrete and go to the building application with an innovative panel design under real climate conditions in the field. Monitoring of the test buildings with and without mPCM showed that developed microencapsulated PCM-concrete composite panels helped to maintain thermal comfort in buildings with a change in indoor air temperature with respect to reference building reaching 2 degrees C, which corresponds to up to 13% energy savings.