The technologies underpinning smart homes offer promising solutions in the realm of assistive living. At present, there are a number of smart home applications being developed with a raft of technologies that provide fragments of the necessary functionality. Nevertheless, there is currently a major gap between these endeavours and the vision of smart homes in which there are adaptive, personalised and context-aware assistance capabilities. To bridge this divide between practice and aspiration, this paper introduces semantic smart homes – a novel conception whose aim is to move from the current state of the art of smart home technologies to the future infrastructure that is needed to support the full richness of the smart home vision. We present a conceptual system architecture for semantic smart homes and elaborate functions and explore the interplay of constituent components. The paper focuses predominantly on the methodology of semantic modeling, content generation and management. We illustrate the potential of the semantic smart homes metaphor through a number of use scenarios.