Buildings have a major impact on the health and well-being of people and to the environment. Old buildings use resources, form waste and are expensive to maintain and operate. Achieving to have zero waste buildings are a practice of building design, construction and operation to increase productivity and decrease energy consumption, to use less resources, to reduce the amount of waste and the negative impact on the environment, and to reduce costs during the life cycle. This research represents building modernization model which creates knowledge-based decision-making method for old public buildings refurbishment seeking to reach the best energy performance during design stage. Using digital systems and simulations this method performs already expected building energy consumption in a quickest and economic way. This model is BIM-based where design and refurbishment are based on pre-built indicators which allows assessing the building energy demand and eco-building parameters.