I doubt that in 1916 the energetic heating demand was determined including solar radiation and air tightness. This has only recently become common practice in Germany.
Translation of a Wikipedia-Artikels (no engl. sister page, Original see link):
The Energy Saving Ordinance replaced and merged the Thermal Insulation Ordinance (WSchV) and the Heating Installations Ordinance (HeizAnlV).[8]
:
Its first version came into force on 1 February 2002, the second version (EnEV 2004) in 2004.[9] In order to implement Directive 2002/91/EC on the energy performance of buildings, a new version was drawn up which was valid from 1 October 2007.
The EnEV 2007
On 24 July 2007, the Federal Cabinet passed an amended Energy Saving Ordinance.
The following aspects of the new ordinance have been significantly changed or newly added in comparison to the regulations described above:
- Requirements for non-residential buildings
- Procedures for the energy evaluation of non-residential buildings
- Consideration of alternative energy supply systems
- Consideration of summer thermal insulation
https://de.wikipedia.org/wiki/Energieeinsparverordnung