The German Energy Saving Regulation (Energieeinsparverordnung – EnEV) 2009 came into force on 1 October 2009. Every owner filing an application for a building permit or submitting notice of building works after 1 October 2009 is obliged to comply with the energy-related requirements imposed by EnEV 2009 if building a new building. Compared with the requirements imposed by EnEV 2007, EnEV 2009 increases the requirements for the overall energy efficiency of buildings by an average of 30%. The thermal insulation of new buildings' envelopes must on average be 15% more effective. The reference building procedure that has to date applied only for non-residential buildings will now apply for the calculation of the energy related requirements for residential buildings, too.