A In this work, the effect of outdoor air relative humidity on the air temperatures at the cooling coil inlet and exit, temperature in the conditioned space, cooling coil capacity, exergy destruction and exergetic efficiency are experimentally carried out. In the experiments performed, by means of a humidifier, the outdoor air relative humidity is increased from 20% to 80% while keeping constant the total air volume flow rate as 12 m³/h, outdoor air dry-bulb temperature as 35 °C, ratios of outdoor and return air volume flow rates as 60% and 40%, respectively. By means of a computer program improved, the cooling coil capacity, exergy destruction and exergetic efficiency is calculated. The energy and exergy analyses are carried out by Engineering Equation Solver (EES) which is commonly used in the analysis of thermal systems and contains thermo-physical data of the fluids in its library. As the outdoor air relative humidity increases, all of the parameters such as the air temperatures at the cooling coil inlet and exit, temperature in the conditioned space, cooling coil capacity, exergy destruction except for the exergetic efficiency increase.