In the EU, about 12% of the greenhouse gas emissions derive from buildings. To decrease the emissions from buildings, more energy-efficient technologies must be implemented. Drivers for the implementation of energy-efficient technologies are important to achieve this. Interviews were conducted with different actors within a city district development project to find drivers for the implementation of energy-efficient technologies in buildings. These drivers were connected to different phases of a building project to see when they have the highest potential impact. Connecting drivers to various phases of the construction process has not been explored before. In conclusion, drivers have the most impact during the Planning Program phase and the Project Planning phase. The most mentioned drivers are Cost reduction from lowered energy use, More knowledge within the building industry both stated by ten of 18 respondents, Long-term perspective at client, and National requirements and client demands both stated by eight of 18 respondents. The most prominent driver seems to be economic gains, and LCC calculations for showing potential economic gains are therefore a very important tool. Education with a subsequent certification on working with energy-efficient technologies and building techniques can be a driver and would also combat the lack of knowledge within the business. In-house knowledge at the client, Long-term perspective at the client, and Client demands are three great drivers. Clients in building projects should therefore aim to have good in-house knowledge, and a long-term perspective to be able to set the right requirements and drive for energy-efficient technologies.