Roughly 97% of the European Union (EU)’s building stock, amounting to over 30 billion m2, is not considered energy efficient, and 75 to 85% of it will still be in use in 2050. Defining a pathway towards a ‘highly efficient and decarbonised building stock by 2050’ is a fundamental pillar of the revised Energy Performance of Buildings Directive (EPBD), requiring the transformation of the majority of buildings from highly inefficient to, at least, nearly zero-energy buildings.