In this work advanced energy analysis method for optimal building retrofit design was developed and described. Method is based on Building Information Modelling (BIM) approach with the use of building energy simulations (BES) for the purpose of building retrofit feasibility and selection of optimal building retrofit solution. First, description of BIM-based approach from the perspective of energy analysis throughout the life cycle of the building (from planning, through construction to building exploitation phase) was described. Afterwards, overview of necessary information for creating BES model and list of possible data providers was given. After that followed the literature review of data collection methods, mostly methods for collection of data about geometry of the building and thermal properties of building envelope. Methods listed in this work are both usual data collection methods for energy analysis of a building and advanced methods still in research. In this work sensitivity analysis was necessary for assessing the importance of input variables to BES in relation on output variable. To include this, overview of most common sensitivity analysis methods used in building energy analysis was given in this work. Sensitivity analysis method selected for this work is regression method. Example of method for selecting the optimal retrofit solution of a building is given in this work. Two BES models were created for high school building located in Helsinki, Finland: simple model with approximated values and detailed model with acquired information of the building. Simple model was used for feasibility analysis of retrofitting the school building, while detailed model was used for selection of optimal retrofit solution. Finally, both of BES models were compared with their input and output variables from simulation.