The operating temperature of building integrated photovoltaic cells is a key factor in terms of energy efficiency. In order to cool them by natural convection, they are mounted in a double-skin façade configuration, meaning that they are separated from the building wall by a ventilated air channel. Identifying and analysing the physical phenomena governing the air flow and heat transfer in this vertical channel are therefore essential to improve cell-cooling. This analysis can only be performed by detailed numerical simulations coupled with experimental studies to validate the results. In the present work, an experimental model is developed in order to study the coupling between the flow and heat transfer of a natural convection flow in a vertical channel. An original approach is taken, using water as the working fluid to avoid radiative heat transfer and obtain a pure convective flow. First the experimental set-up, the boundary conditions and instruments used to obtain reference data are described. Then simultaneous temperature and velocity measurements are provided. Finally, an analysis of the mean velocity and fluctuations profiles shows a change of the flow behaviour occuring at a sufficiently high Rayleigh number.