If detailed information about the structure of building components (such as walls and ceilings) is unavailable, estimation is carried out in accordance with DIN/TS 12831-1:2020-04, based on the year of construction.
For different construction years, specific data is available for each building component, including characteristic U-values. If no specific wall constructions are recorded for a room, the U-values are automatically determined according to the building age class.
Source(s): DIN (2020): DIN/TS 12831-1:2020-04; Bundesanzeiger (2020): Bekanntmachung der Regeln zur Datenaufnahme und Datenverwendung im Wohngebäudebestand;