Heating, ventilation and air-conditioning, HVAC, systems represent a significant energy use in Europe, around 50% of total energy use in buildings. Conventional HVAC systems are mainly based on direct expansion units, whose use of 100% outdoor air leads to high energy use. Then, different innovative and efficient air-cooling systems could be an interesting alternative to approach Nearly Zero Energy Buildings, nZEB. One of these efficient solutions is the technology of indirect evaporative cooling. This work was based on the experimental evaluation of a regenerative indirect evaporative cooler, RIEC. Several empirical tests were carried out under different inlet conditions: inlet air temperature values between 29 °C and 43 °C, TOA, and inlet air humidity ratio values between 9 g/kg and 13 g/kg, 𝜔OA, were considered. A constant inlet air stream, V0A, and a constant supply air stream, SA, were adjusted during these tests for a steady-state period of thirty minutes each. The response variables which evaluated the thermal behaviour of this RIEC system were: (i) dew point effectiveness, εdp; (ii) wet bulb effectiveness, εwb. High values of εdp and εwb were reached when the inlet air humidity ratio was 9 g/kg, around 0.87 and 0.92, respectively. However, low values of dew point effectiveness, 0.71, and wet bulb effectiveness, 0.78, were showed when the inlet air temperature was 29 °C and the inlet air humidity ratio was 13 g/kg. According to the results that this study showed, the RIEC system could be an interesting alternative in spaces where improved indoor air quality is required by using 100% outdoor air. This type of systems could achieve high values of thermal performance, specially under hot-dry climatic conditions.