Several assessment methodologies have been proposed to measure the environmental impact of buildings. However, these methodologies require processing data which is often not available or requires a high integration effort. In this paper, we propose an ontology to describe the use and reuse of prefabricated components in buildings. This ontology describes the relation between the physical object, the building component, with the digital object that represents the element in the building information model. We show that this ontology can be used to answer questions like which building components have been reused and which activities were involved in the life cycle of a building.