Natural ventilation is proved to be an essential tool to ensure high indoor air quality standards, while limiting energy use in buildings. This is particularly true in existing buildings where it is difficult to implement controlled mechanical ventilation with heat recovery systems. So, particularly in intermediate and warm seasons, natural ventilation still plays a major role in ensuring good air quality. However, one critical issue when considering natural ventilation is represented by the significant reduction of the sound insulation properties of the window. In order to address this issue, scientific literature has been proposing different solutions including partially open windows and, more recently, metamaterial-based windows. The present work aims at investigating the ventilation performance of a selection of five solutions (including one conventional window, one plenum window, one parallel window and two metamaterial-based), studied by means of a 3D numerical model developed in Comsol Multiphysics. The windows are compared taking into account the discharge coefficient (Cd) and air change per hour (ACH), as figure of merit, as well as the qualitative analysis of air flow patterns, distribution and velocity, under turbulent flow conditions. The results suggest that metamaterial-based windows offer ventilation performance similar to traditional openings and can be a suitable alternative, thanks to their improved acoustic comfort.