During the last decade, steel constructions with glazed facades became popular for commercial buildings in Greece. Moreover, expensive metal, natural stone, marble, ceramic, granite as well as special glass is employed for aesthetic and energy efficiency reasons. This creates opportunities for the introduction of Photovoltaic (PV) modules in double facades. PV modules on south-facing building walls are better placed at a distance from the wall to allow heat rejection and avoid overheating and efficiency loss. Exploiting the rejected heat of the PV modules is also a challenge. In this paper, we examine an improved concept of incorporating PV modules to the south facades of an office building, exploiting both the electricity produced and the heat rejected by the module, to increase building energy efficiency. The PV modules are integrated to the building wall by means of a double facade, which employs intervening ducts for ventilation purposes. The ducts are heating outdoor air, which is employed to cover the ventilation needs of the building, as well as a part of the heating loads. Simulations for typical winter and summer weather and solar insolation conditions are carried out to investigate the building's energy performance improvements. (C) 2010 Elsevier Ltd. All rights reserved.