Over the last few decades, there is a clear target for reducing energy needs in the building sector. The above objective can be achieved both by renovating the existing building stock and/or by constructing new buildings that will meet the characteristics of zero or nearly zero energy buildings. In order to construct or renovate a building into a zero or almost zero energy building, different passive, active and hybrid systems can be used. One such system is a solar air heater collector. The above system was installed in the south facade of the outdoor test cell (ZED-KIM (Zero Energy Demand – Kimmeria)), located at the Campus of the Environmental Engineering School, DUTH at Xanthi (Greece). In the present study, the monitoring results of the solar air heater collector and its contribution to cover the cooling load of a building will be presented. The system was monitored under real weather conditions for the period June 2017 to August 2017. This period was separated in two sub-periods. In the first one, the system operated as a solar air heater and with the appropriate modifications air from inside the test cell was passed through solar collector and hot air was rejected out. In the second sub-period, a ventilation inlet was added in the north facade of the test cell, and the system operated as a solar chimney. The heating load that rejected out in the first sub-period was 12 KWh and in the second sub-period was 58.5 KWh. In other terms the cooling load of the test cell was reduced by 70.5 KWh for the whole period of measurements. In addition the cooling load for the specific climate zone of Greece and for 20m2 cooling space was 488 KWh so there was a reduction of 15 percent. Furthermore, it was noticed that the thermal efficiency of the system increased above 50 percent between 1st and 2nd sub period, with values being 16% and 34% respectively. Based on the above results, it is concluded that even in hot weather conditions prevailing in northern Greece, the use of a solar air heater collector with the appropriate modifications can cover, in a significant degree, the cooling load of a building and in conjunction with other passive and active systems it can lead at a nearly zero energy building.