To reach the EU decarbonization objectives, it is urgent to trigger more investments targeting energy retrofit for buildings. Introduced at European level since 2002 within the Energy Performance of Buildings Directive (EPBD), Energy Performance Certificates (EPCs) represent a relevant instrument supposed to be strongly structuring for the assessment of buildings energy performance, decision support regarding energy retrofit projects, development and articulation of financing instruments (public and private), benchmark of building assets and market value recognition. However, the potential for this instrument remains largely under exploited because of several challenges: The improvement in terms of reliability – referring to results variance depending on the assessor, input data and calculation tools, the lack of understanding between predicted and actual energy performance, etc. – represents a crucial issue to unlock confidence, decision support, and articulation for financing. Besides, to engage end-users towards deep renovation, the certification is to structure tangible pathways to ambitious targets with respect to building overall quality and energy performance improvement. Furthermore, the design for the overall process and certification outputs must be even more owner and occupant-centric and allow European benchmark and public policies analysis. To tackle the above challenges, and leveraging on the business operations of consortium partners, EPC RECAST has set a well-structured process and a toolbox supporting the development, implementation and validation of a new generation of Energy Performance Assessment and Certification, with a deliberate focus on residential buildings, more specifically existing ones, for which retrofit is one of the most challenging and pressing issue.