Nearly Zero-Energy Requirements and the Reference Buildings

According to the recast of the European Directive on the Energy Performance of Buildings Member States shall ensure that (a) by 31 December 2020, all new buildings are nearly zero-energy buildings; and (b) after 31 December 2018, new buildings occupied and owned by public authorities are nearly zero-energy buildings. It is the responsibility of the Member States to define the measure of nearly. This paper analyses the challenges of setting the requirements. In order to ensure that the requirements are realistic, they should be checked on reference buildings. The statistical evaluation of a large building sample as reference is recommended instead of using a few typical case studies. The potential and obstacles of various renewable energy sources are analysed for favourably located buildings and for buildings in urban areas, where solar access and space may be limited. Urban buildings will be able to comply with the requirements only if energy production from renewables on a district or urban scale (off-site) is realized and acknowledged in the energy balance. A case study of apartment buildings shows the future importance of the ratio of the energy collecting surface to the floor area.