Data show that people with lower level of key competences have up to 1,8 times more probability to be unemployed than those with higher levels. Hence, these unskilled adults lack the necessary "skills" to carry on with higher level of training.This is the problem that we dealt with: the EU construction industry is a common destination of people from school failure, whose low knowledge base (arithmetic, calculation), hinders them to learn and perform more complex tasks. This failure dooms, in the best-case scenario, these workers to perform tasks of peonage despite the fact that they could develop competencies of higher responsibility or, in the worst case scenario, to the long-term unemployment.Thus, this project has designed and applied a training system (AR.KEY) for non-qualified workers from construction industry, with the aim of improving their mathematical competence and basic skills on science and technology, keys to successfully follow up their training and hence their professional career.To do so, AR.KEY is organized in learning outcomes using EQF methodology and based on Augmented Reality (AR), which is a live, direct or indirect, view of a physical, real-world environment whose elements are augmented by computer-generated sensory input such as sound, video, graphics or GPS data, enhancing one’s current perception of reality. The final application is available for using on tablets and/or smartphones on markets such as Google Play (ANDROID) or Apple Store (APPLE).Therefore, the training system allows the improvement of the professional skills of unskilled workers from the building sector in those productive processes related to the comprehensive refurbishment of a building. For this purpose, the system has been structured in training modules sequenced in a very easy way, being supported by AR as well as other multimedia resources, in order to train students in those key competences necessaries to better understand more complex procedures such as the refurbishment, maintenance and conservation of covers, installations, facades and structures, or the energy restoration (energy efficiency and/or renewable energy systems) of a building.8 WP were set up to achieve project objectives:1. Initial planning and overall management of the project 2. Identification of the commonest refurbishment processes3. Identification of key competences needs4. Definition of contents in terms of learning outcomes5. AR.KEY System Development6. AR.KEY pilot7. Valorization of results and sustainability8: Project divulgation and communication Partnership was formed by 7 partners coming from 5 different countries, experts in vocational training in the building industry.