A new concept of integrating Photovoltaic modules to south-facing walls of a building is developed. The feasibility of the concept is studied by means of experiment, CFD computations and building energy simulation. An air gap between the backsheet of the modules and the building wall is employed for circulating outdoor air to cool the modules, keeping their efficiency high. The heated air is exploited by the HVAC and service water system, thus improving building energy efficiency. A testing device was designed and subjected to extensive indoor and outdoor testing. The flow and heat transfer investigation of the device was supported by CFD modeling that helped to determine more accurate wall heat transfer correlations that are used to improve the respective sub model of the building energy simulation, to predict the overall effect on the energy performance of the modules, by means of the electricity produced by the PV panels, the heating energy gains and their overall effects on the energy rating of the building. Measurable improvements in the thermal gains of the building can be succeeded by improved design of the backsheet.