The use of solar energy for the heating of buildings, via storage walls, has been extensively studied and several components have been developed since the Trombe works. The standard Trombe wall has two main drawbacks. During cold and cloudy winter days, it causes important heat losses and thus discomfort to the occupants. In summer it creates important and undesired inputs. These drawbacks can be eliminated by a more complex design such as the composite Trombe wall. In connection with architects such as J. Michel, we designed a massive solar wall, with an insulating panel located just behind it. A ventilated air layer exists between this panel and the wall. Vents located at the top and the bottom of the insulating panel allow air circulation and thus energy inputs to the building. A prototype was built into a test cell at Cadarache and was tested for 2 years. This allowed various climatic conditions and operation modes to be examined. We used tangential gradient type heat fluxmeters to determine the thermophysical properties of the massive wall and we quantified the heat transfers in the ventilated layer and to the building. The data obtained are now being used as input for a software to assess the performance of this improved component.