Split-type air-conditioning systems are widely deployed worldwide, due to their low costs, ease of operation and simplicity of control. From engineering perspective the installation of the outdoor components of the AC units should be done on the building façade, to ensure good air circulation around the units. However this may interfere with the architectural design and the aesthetics of the building block. Therefore alternative plant spaces for the installation of those units are often selected, which include light wells or the units being recessed. Installing those units in light wells may lead to units overheating that leads to low units’ performance or units troubleshooting. Two cases of mechanical ventilations solutions (by exhaust extraction or by fresh air supply), for this problem are suggested and investigate in this study using CFD modeling for different arrangements of the units in the light wells. The results show that (i) mechanical ventilation of the building light well is necessary in case of installing the AC outdoor units in it, (ii) in case of exhaust extraction ventilation, the AC units’ COP and power consumptions enhance as the installing level of the outdoor units increases and the opposite is true in case of fresh air supply ventilation, (iii) the outdoor units installed at lower levels (first two floors) in case of fresh air supply ventilation has bitter performance than the case of exhaust air ventilation and the opposite is true for units installed at higher levels, and (iv) the layouts arrangements of the outdoor units in light well has no effect on the units’ performance in case of using mechanical ventilation.