Since the mid 80'erne working as scientist with focus on reduction of the energy consumption in buildings in both national and international projects. At the beginning in a research group on low energy buildings at the Danish Technical University and since 1992 at Danish Building Research Institute, SBi, Aalborg University.

Here focus have been on energy improvements and analyses of the energy saving potential in existing buildings. Additionally, I have been co-worker in development of the BSim simulation tool, an advanced computer tool for dynamic simulation of energy-, moisture and indoor climate conditions of buildings. Furthermore I have worked on analyses of the possibility to integrate sustainable energy sources, especially solar cells, in the thermal envelope of buildings. In the recent years, I have been involved in implementation of the Energy Performance of Buildings Directive from EU, both nationally and internationally as well as analyses of the energy saving potential in existing buildings.