The Internet of things (IoT) is a new paradigm that combines aspects and technologies from ubiquitous and pervasive computing, wireless sensors networks, Internet communications protocol, sensing technologies, communication technologies and embedded devices. The building IoT is not only able to collect information from the environment, but also to interact, control and interconnect the various silos of fragmented systems within buildings. The huge number of interconnected devices as well as the significant amount of data generated by them provides unprecedented opportunities for buildings to meet their economic, sustainable and comfort goals. These technologies are merged together with building information systems in order to form an environment where the real and digital worlds meet and are continuously in a synergetic interaction. This intelligent environment forms the basis of the concept of intelligent buildings. In this article the authors elucidate the concept of intelligent buildings, the key features and the driver technologies of IoT and the physical–digital integration within buildings. They present intelligent buildings applications enabled by the IoT, and research challenges and open issues to be faced for the IoT realisation in intelligent buildings.