The German Energy Saving Ordinance (EnEV) addresses the energy efficiency of both the building envelope and building services - the plants for their part are operated with energy sources, which are made comparable among each other with primary energy factors (PEF). In the scope of the EnEV certain limits need to be followed regarding building components and / or regarding primary energy demand of the entire building. Since the primary energy factors have decisive influence on the dimension of the to be calculated yearly primary energy demand, the determination has effects on the choice of heating technologies and their energy sources or on the internal relation of activities to increase efficiency of building envelopes and building services. Against this background, the definition and the significance of primary energy factors as well as their steering power towards climate protection targets (CO2) and other goals are investigated in this study. The outcome of the study shows that in particular due to the following two reasons, a readjustment of PEF within EnEV is deemed necessary:

1) In many cases the primary energy factor is an inappropriate measurement in order to determine greenhouse gas emissions of a heating system or final energy source and therefore has an only limited steering effect in terms of climate protection.

2) Primary energy factors (PEFne) that amount zero (e.g. district heating), are close to zero (e.g. wood) or perspectively approach zero (e.g. power), lose their steering power for energy efficiency of buildings. Even though thereby the formal demands on the accounting of buildings are fulfilled, other important aspects as e.g. resource availability and import dependency of energy sources or other effects linked to primary energy provision are neglected.

Therefore in the discussion paper first approaches are outlined, how PEF for logical reasons could be further developed methodically in the EnEV or if eventually further or other indicators should be considered in order to characterise ecological performance of buildings.