This paper summarizes a PhD-project that is currently under completion at Delft University of Technology, Faculty of Architecture, Building Physics Group. The general problem addressed in this project is the integration of building simulation tools and building design. This problem has been narrowed down to computational support for one specific type of building design decision: the selection and integration of one or more energy saving building components like solar walls, advanced glazing systems, sunspaces and photovoltaic arrays into a given building design. The paper provides an overview of the main research efforts that were carried out during the research [Computational Support for the Selection of Energy Saving Building Components, PhD thesis (in preparation), Building Physics Group, Faculty of Architecture, Delft University of Technology, 2004]. Based on results and on views that have been described in earlier publications (e.g. [Beter ontwerp door gebouwprestatie-simulatie? in: Proceedings of the Third IBPSA-NVL Conference, Petten, The Netherlands, December 2001]), the paper then will identify relevant, challenging issues for future research in the area of integration of building simulation tools into the building design process. Specific attention will be paid to issues related to the use of different categories of tools (simulation tools as well as other instruments) for the development of new, energy-efficient building design concepts. (C) 2004 Elsevier B.V All rights reserved.