In daytime operation, the warm fresh air passes through a PCM storage unit, where it is cooled and introduced into the room. This cooling process is effective until the previously solid PCM in the storage unit has liquefied as a result of the heat it has absorbed. In nighttime operation, the colder outdoor air passes through the unit and the PCM solidifies again and can thus be re-used to cool the room during the day. Depending on the design of the latent-heat storage unit, a pleasant room temperature can be ensured for up to 10 hours during the following day.

The façade ventilation unit with PCM module obtains the fresh air through an opening in the façade and discharges it into the room. In case of very high outside temperatures, the mixing of secondary air or sole secondary air operation means that the PCM in the storage unit melts at a slower rate and the storage unit does not discharge so quickly.

In summer, during the nighttime use of the storage unit, the building structure is also cooled (night cooling). This means that the unit can be used in rooms with a cooling load of up to 60 W/m².