You do indeed need the energy performance certificate based on demand (Bedarfsausweis). This must be calculated after a building survey, a process that is quite time-consuming and causes costs starting from approximately €400,-/500,-, depending on the size and complexity of the property. It is normal that architects or building authorities also fail due to the pitfalls and contradictions of building regulations or the Energy Saving Ordinance. Both legal constructs are occasionally contradictory in themselves.