A building refurbishment of a commercial building from 1960, publicly sponsored by the German Ministry of Economy and Technology within the EnOB research initiative was done by the Remscheider Entsorgungsbetriebe (REB). By the refurbishment, primary energy was reduced from 440 kWh/m²y to 100 kWh/m²y, in this case less than 60% compared with the reference building. The refurbishment includes constructions with transparent insulation materials and solar water heating. You find further information on the EnOB-homepage http://www.enob.info. EnOB is an abbreviation of the initiative "Research for energy-optimised construction".