The existing built environment is responsible for 40% of total energy consumption in Europe. However, the replacement rate of the existing building stock remains at only 2% per year. As it stands in fact, the design and construction process is inefficient and effective communication does not always occur among stakeholders in the process. The problem grows exponentially for renovation projects, as the project increases in complexity due to the additional constraints related to existing structures and occupants. Within NewTREND project, a new approach for an effective collaboration within refurbishment projects is proposed. The new retrofit design methodology takes into account the best practices of existing methodologies but includes the adoption of simulation tools at early design stage, ensuring energy efficiency is included as a key criteria. The methodology sets recommendations for the data collection, enabling a range of analysis, including energy modelling, to be conducted more easily and from the very beginning of the design process. All the phases of refurbishment, from data collection to concept creation to operation, through detailed design and construction are addressed and energy and performance is considered as a priority for the design. The intensive participation of building occupants into the retrofit design is foreseen.