definition
strict definition
KfW 40
A German efficiency house class, for a building using 40 per cent of the primary energy of the reference building.
KfW 40 means the building uses 40 per cent of the primary energy that the reference building defined by German energy law would use.
The number is a percentage and lower is better, which reverses the intuition that a higher number means a better building.
The classes govern eligibility for subsidised loans from the German state development bank, so they appear on buildings financed through those programs. The thresholds have been tightened repeatedly, so a class carries the year it was awarded.
