TRAIN4SUSTAIN (T4S) will stimulate demand for skilled construction sector professionals (architects, contractors-SMEs and workers) through raising acceptance of regional and national qualifications and skills on the EU construction market. To this end, comparability of national qualifications and sustainable energy skills is key for increased transparency and penetration power in the market. T4S will tackle the issue of mutual recognition so that training accredited in one country is recognised easier in another country. Taking advantage of already available transnational energy skill qualification frameworks for building professions, like the BUILD UP Skills initiative, Prof/Trac scheme or the ones produced by the BIM community, and the recently developed EU framework for energy and resource efficient buildings (e.g. Level(s) ), T4S will focus on acting at market level. T4S project will foster a common understanding of sustainable energy skills across Europe by promoting a competence quality standard, a European Skills Registry and a Skills Passport for facilitating transnational recognition of learning outcomes and skill levels of existing qualifications and vocational trainings.