Analysis and identification of the energy efficiency potential; Development of an energy saving concept & strategy.The OMV head office in Vienna was getting occupied in the year 2009. The daily building operation was performed by OMV in-house personnel while the facility management was provided by an external company. The building users were facing difficulties in properly operating the HVAC system to satisfy standard indoor comfort parameters such as indoor air temperature, air quality, and draught. Further to this, energy costs were higher than originally expected. The Consultant was assigned to analyse the energy efficiency potential and to develop an energy saving concept for the head office OMV.