This paper describes the office building of V&R The Solarcompany in Heusden-Zolder (Belgium). The building has very low heating and cooling demands, due to a building fabric designed according to the Passive House standard, combined with well controlled strategies for night ventilation, a ground-air heat exchanger and solar shading as well as efficient heat recovery from ventilation air, when needed. The remaining energy demand is covered by extensive use of solar energy in combination with a ground-coupled heat pump. This combination makes the building an interesting example of a (near) Net-Zero Energy Solar Building (NZESB). Therefore it was chosen as one of the test-cases for Subtask B of the IEA SHC Task 40/ECBCS Annex 52 project "Towards Net Zero Energy Solar Buildings". For these case studies monitoring data will be available, together with detailed simulation results and a description of the design process. This paper focuses on the study of different parameters that are needed to create a calibrated energy model using EnergyPlus and continuous monitoring of all relevant data from the building, the HVAC system and the renewable energy production. Furthermore the documentation and further improvement of the design process by using the IDM method to establish process maps and exchange requirements is described.