Buildings are one of the major contributors to energy use and CO 2 emissions. The energy used in buildings accounts for about 40% of the total energy use in Europe. The main aim of the IntUBE project (http://www.intube.eu) is to develop intelligent Information and Communications Technologies (ICT) to improve the energy efficiency of these buildings. IntUBE will primarily focus on integrating existing software functionalities using open standards and their open source implementations. Based on the open data from multiple life-cycle stages (especially 'design' & 'operate') new advanced services will be developed to inform inhabitants in intelligent ways of how to change their energy consuming behaviour in ways that reduce energy consumption and improve comfort. This paper will show how W3C Semantic Web technologies  like Resource Description Framework (RDF), Web Ontology Language (OWL) and SPARQL semantic query language can be used to its fullest to model the buildings, their installations, usage and performance; 'as-planned' in the design stage and 'as-built' in the operational stage.