Used in variables: energy_reference_area

Building construction year

age
├── <1920            # Buildings built before 1920
├── 1920-1945        # Buildings built between 1920 and 1945
├── 1946-1960        # Buildings built between 1946 and 1960
├── 1961-1970        # Buildings built between 1961 and 1970
├── 1971-1980        # Buildings built between 1971 and 1980
├── 1981-1990        # Buildings built between 1981 and 1990
├── 1991-2000        # Buildings built between 1991 and 2000
├── 2001-2010        # Buildings built between 2001 and 2010
├── 2011-2017        # Buildings built between 2011 and 2017
├── >2017            # Buildings built after 2017