Cavity wall is often proposed in the building envelope design as a solution for improving the thermal comfort of the inhabitants and reducing the adverse condensation effects on the building fabric. In order to evaluate the thermal effect of ventilated air gaps on building energy demand and comfort, an experimental ventilated cavity wall has been built and tested. The cavity wall separates two ambients at different temperatures that are assumed to be constant over the time required to perform the experimental analysis. The experiments were carried out for Rayleigh numbers between 2x102 and 2x104 and the results have been compared with the results of a proposed CFD code. Furthermore, an experimental analysis on the ventilated cavity wall is performed against the reference case of closed cavity.