A number of energy-saving retrofit measures are simulated on a base-case building situated in Stockholm, Sweden. The base-case building is modelled on an existing building, and data for the thermal resistance of the building envelope as well as data for internal heat gains, are derived from the actual building. The retrofit measures studied range from single measures carried out on the HVAC system or on the building envelope, to combined measures carried out on the HVAC system and the lighting system simultaneously. Sensitivity analyses using an alternatively designed base-case building, have also been carried out. The simulation results show that substantial energy savings can be achieved.