Due to the increasing energy use and greenhouse gas emissions related to HVAC applications in the residential sector, thermal energy storage with phase change materials has caught considerable attention in the last years. Their attractive storage capacity can be adapted to meet the energy needs of buildings. In this work, the design process of a prototype of an air-PCM unit is described, and the corresponding experimental tests are detailed. These experiments were carried out on a plus energy house prototype located in the Southwestern France, during the summertime of 2017. The thermal performance of this unit was assessed through indicators such as indoor air temperature, the operating time, and the Discomfort Degree Hours (DDH) within the house. The results suggest that the unit limits the indoor air temperature rise during its operation, keeping the temperature within the thermal comfort and therefore contributing to decreasing the thermal discomfort.