The paper concerns the theoretical and practical problems of computer aided modeling and energy analysis of newly designed and existing buildings and presents the new results of development of the system MEA (Modeling and Energy Analysis). The factors are pointed out determining the development of the program package MEA. The paper describes the functionality of the created and extended program tools, the methods of construction of the integrated geometric models and analysis of the building model and its database, the data structures used in different designing stages, the user interface, the variant design procedures based on heuristic principles. An example of the analysis and the evaluation of the design solutions of the building under renovation based on energy and economical criterions are presented.