This work is a contribution to the highlighting of the secondary flows in vertical cavities with high aspect ratio, in laminar regime. Multicellular flows in high aspect ratio two-dimensional cavities, such as those encountered in insulated glazing units, are the main focus of this investigation. Numerical and experimental results are presented. Authors investigate a numerical study on the temperature field and the associated Nusselt number, and on the velocity field. In the experiments, Particle Image Velocimetry is used to obtain the velocity field. The numerical and experimental results show the presence of secondary cells.