The legal background for the assessment of the energy performance of buildings and energycertificates in Germany will be changed in October 2009. Beside the tightening of the requirements byabout 30%, a significant change will be made at the calculation of residential buildings. Up to now thecalculation has to be performed by using the so-called simple approach (EN 15603) by applying theoutdated European standard EN 832 in combination with the European Standard EN 14335 withnational boundary conditions. From October the calculation can also be performed according to theso-called holistic approach (EN 15603) by applying the DIN V 18599, the German standard application of the EPBD related CEN standards from the EU mandate 343.The DIN V 18599 differentiates the calculation into mechanical ventilation, natural ventilation byopening the windows and ventilation due to infiltration through leakages. That means that the energyeffort in residential buildings for ventilation can now be considered in a much more detailed level.In this paper two typical residential buildings are calculated with various configurations of theventilation system. This might be as well a mechanical ventilation system with heat recovery but alsoonly naturally ventilated buildings. This work will give an overview, whether the energy performanceand especially the energy for ventilation are significantly different, when calculated with the two standards.