Research partners of 10 different countries are developing a computer tool in the framework of IEA ECBCS Annex 36, which helps decision makers to include the most energy-efficient and economic technical retrofit measures into the retrofit of their educational buildings. The tool, which will be ready for distribution at the end of 2003 consists of several parts such as : A) the problem related recommendation part in which the building owner or care-taker will find solutions to existing problems of his building including detailed information on the retrofit measure, case studies in which the same problems were taken care of and an estimation of the pay-back period of the measure B) the case study viewer that consists of descriptions, results and lessons learned out of more than 30 retrofits of different educational buildings in different countries C) the retrofit measure viewer with information on various energy technologies for retrofit measures such as improvement on the building envelope, the heating, the ventilation and the cooling system, the lighting and the electrical power D) the performance rating part in which the decision maker can rate the energy performance of his building in comparison to national surveys E) the concept development part. Here the technical staff of the decision maker can assess suitable measures for their building. The input part allows adapting the building geometry, the construction and the heating and ventilation system to the existing state of nearly any school or university building. Additionally various retrofit measures can be evaluated and combined with each other. As result the energy demand and the cost for each combination is given. By that an energy retrofit concept can be developed which will be further refined with the help of regional consultants. An exemplary application of the tool will be shown with respect on ventilation strategies and their influences on the primary energy demand.