The potential for optimum energy use and conservation of natural resources in representative southern and northern European office buildings is evaluated using the new European TOBUS methodology and software for office building refurbishment. Various scenarios are being accessed fur energy and water conservation in office buildings. The proposed retrofit actions focus in the areas of space heating and cooling, artificial and natural lighting, service hot water, office equipment, elevators and sanitary water. The resulting conservation and related costs are taken into account in order to help the auditor classify the retrofit actions for an audited building. The TOBUS methodology and tools have been implemented to study four Hellenic office buildings and two from Denmark in order to demonstrate the applicability of the overall approach. Energy conservation in Hellenic and Danish buildings range for space heating from 5 to 71 and 0.5 to 6%, for space cooling from 1 to 38 and 4 to 20%, for artificial lighting from 40 to 53 and 26 to 62%, for office equipment from 13 to 62 and 13 to 87% and for elevators at 35 and 23%, respectively. Sanitary water conservation can reach 74% in all audited buildings.