An integrated simulation system for the building services design and facilities management purposes is being developed by Olof Granlund Oy. The system covers the thermal simulation needs of the whole building life cycle from the preliminary design to renovations. The main components of the simulation system are simulation database, result module, calculation engine, which are all built in to a user interface RIUSKA, and building geometry modeller, SMOG. The building geometry modeller generates a 3-D surface model of the building and has IFC 1.5 import/export capabilities. The calculation engine of the first version is DOE 2.1E. The simulation database is linked to other design databases and design programs so that redundant input data is avoided.