Ecological efficiency of buildings is becoming increasingly important in the building sector not at last because of its stronger presence in legislation (e.g. EnEV 2006 in Germany). To be ecologically efficient a building mostly requires full functionality that often depends on a complex interaction between different building features, aspects of the surrounding, climate conditions, and not at last the awareness and behaviour of building managers and users.Literature indicates that an implementation of future building users in the process of planning and construction (cp. Linneweber, 1993) and the building planners' higher understanding of the users perception can improve later building performance (cp. Rambow 1995, 2000) According to this a thorough planning phase would be needed here, that is sensitive to the different interdependent dimensions of building performance and considers function enhancing procedures like user need analysis and user participation.Perceptions and procedures in building planning and performance are explored in a current interdisciplinary study, focusing office buildings with a special kind of façade system that is said to be 'ecologically efficient'. 4 different office buildings throughout Germany were evaluated using physical measures, structured interviews with building planners and managers as well as user questionnaires. Aspects of planning process and current operation and their dependency on perceptions and experiences of architects, users and building managers were analyzed.Results show crucial threads to efficient building performance: A significant distance in building-related perceptions and expectancies between planners, constructors and user was found. Further the criteria 'ecological efficiency' seemed to be adopted in a more or less 'outward' way that is not grounded on quantitative base rates and expectation values. Finally the complexity of the building itself is not just a special challenge to planners but also to users who need to show contra-intuitive behaviour in parts.The results of the study will directly be implemented to the field through workshops and a planner's handbook. Recommendations will be given related to better ways of handling a building complexity in planning and usage but also in order to enhance the exchange between building planner, managers and users.