Greenhouse is one of the most recent agricultural systems that provides an economic resource by increasing production and allowing crops to be grown all year. In Iraq, this approach encounters an impediment during the summer. As a result of the rapid rise in temperatures, greenhouses are becoming increasingly ineffective. In this season, it is unusable. A two-stage evaporative cooling system was used in this study, with one indirect evaporative cooling heat exchanger and three direct evaporative cooling pads. The performance of the proposed indirect–direct evaporative cooling (IDEC) unit with various settings was tested during the summer season in Kirkuk, with dry bulb temperatures ranging from 45 to 50°C. The results reveal that using groundwater increased the IDEC unit’s efficiency to 98.3%, compared to 67.5% when using direct evaporative cooling. When covering layers were used, solar intensity entering the greenhouse was lowered from 11.4% for a single layer to 28.4% for two layers with one layer of green mesh. In comparison to ambient circumstances and according to the parameters analyzed, the IDEC system employing groundwater results in a decrease in greenhouse temperature and an increase in greenhouse relative humidity. The IDEC unit was verified using TRANSYS software and experimental measurements from a test greenhouse. For the same ambient temperature, simulated and experimental findings revealed that the simulated temperature is lower than the experimental temperature. The percentage difference in greenhouse temperature between the TRANSYS simulation and experimental measurements reached a maximum of 9.43%.