For outsiders, a national energy performance (EP) requirement level is quite a black box. Within the EU Asiepi project (www.asiepi.eu) we are developing a methodology to make a comparison of EP requirement levels possible among member states of the EU.An unexpected finding has been that far from all EU countries consider all energy uses in their EP method required by the EPBD (Energy Performance of Buildings Directive). The energy use for fans, domestic hot water and cooling are among the energy uses which are not taken into account by various countries. This largely complicates the comparison over Europe. What also complicates the comparison is that sets of energy measures are not equally relevant in all climates in Europe. The recast of the EPBD proposes to take into account a cost optimal level. This might be a way of properly reflecting local issues, although developing such a method on European level is a big challenge.