HVAC systems for large industrial buildings usually have large Air Handling Units (AHU) and chillers placed on roofs or in the proximity of the building, interacting with the external environment. Wind plays a crucial role in determining the performance of AHU’s and chillers. At Actiflow we simulate the effect of wind and ambient temperature on the performance of HVAC systems. With the help of CFD simulations, we calculate the pressure exerted by the wind on the building and on different devices, establishing if this has a positive or negative effect on the air handling process. Also, we determine whether ventilation short-circuiting phenomena take place between air inlets and outlets of HVAC systems and we can propose smart solutions for avoiding or mitigating such effects.