By the end of 2017 NEN decided to update the existing national Energy Performance standards in The Netherlands. The planning was to finalise this work within roughly one year. This short time frame was based on the requirement in the EPBD to report to the Commission by March 2020. The new national method should be operational by 2020. It was estimated that final checking and preparing and distributing reliable software based on this national method should at least take one year. It was clear from the beginning that this was a very ambitious time frame, in particular because the new methodology had to meet a number of demands that might not all have been covered by the existing method. Moreover, the goal was to develop a methodology that would be as much as possible in line with the European standards.