In reaction to the European Energy Performance of Buildings Directive (EPBD), existing and newly lanced standard developments by CEN (European Committee for Standardization) were harmonized and synchronized, resulting in a set of about 50 standards addressing different aspects of the EPBD and the implementation of an overall building energy performance calculation method. A few of them address simulation issues: An overview of these is given, focusing on one standard covering system related aspects for buildings with cooling, humidification or dehumidification. It allows for any calculation method, including hourly simulations, as long as the general requirements are fulfilled. In the HVAC domain the variety of systems is very large and there is no general method able to cover this. Simplified calculations may cover certain areas, and the standard gives indications when this is acceptable. Validation aspects are addressed in a very preliminary way, since this is an area for more research.