The European Commission has mandated CEN to produce a set of standards to support Member States for the national implementation of the EPBD. This paper focuses on one of these standards, EN ISO 13790, "Energy performance of buildings - Calculation of energy use for space heating and cooling". It describes the history of this standard which started with a simplified calculation of the energy use for heating of residential buildings only. It describes the current methodology, inclusing heating and cooling, also for non-residential buildings and the 'level playing field' for both simple and detailed methods. The paper also discusses the issues involving the implementation of the methods in the EU Member States and the prospects for the future.