Directive 2010/31/EU
Member States shall take the necessary measures to ensure that minimum energy performance requirements for buildings or building units are set with a view to achieving cost-optimal levels.
"Member States shall ensure that:
(a) by 31 December 2020, all new buildings are nearly zeroenergy
buildings; and
(b) after 31 December 2018, new buildings occupied and
owned by public authorities are nearly zero-energy
buildings." (http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:153:0013:0035:EN:PDF)