In this paper, we propose a holistic approach to raise building efficiency, consisting in: i) a smart ICT-based monitoring and control system, relying on wired and wireless sensors and actuators, that uses the existing lighting infrastructure as cabled data link; ii) an innovative lighting network, low voltage direct current powered, integrating photovoltaic systems and Solid State Lamps (SSLs). Moreover, we discuss compliancy with emerging communication standards, with focus on domotics and building automation.