The concept of Nearly Zero Energy (NZE) – ‘Bijna-energieneutraal’ (BEN) in Belgium – was launched by the European Commission. A European Directive dating from 2010 requires all new buildings to be nearly zero-energy buildings by 2021.

A nearly zero-energy building must conform to the following two criteria:

• the building must have a very high energy performance;
• the nearly zero or very low amount of energy required should be covered by energy from renewable sources, which is also produced on-site or in the vicinity.

Each country determines its own NZE standards

Each country is free to determine:

• how much energy the building may consume;
• which renewable energy sources are permitted;
• how close to the building the energy has to be generated.

An NZE building in Belgium will therefore not necessarily mean the same as an NZE building in say Portugal or Germany.

The standards in Belgium even differ per region

• In Brussels, the passive-house standard will apply from 2015. This is stricter in the area of energy performance, but does not require the use of renewable energy. See also: 'Passive, low energy and zero energy: what is the difference?'
• In the Walloon Region, the same passive-house standard will be introduced from 2017.
• In the Flemish Region, the NZE standard is used, in which the building must have an E-level of E30 or lower and conform to a string of other requirements (see: energiesparen.be - BEN, link in Dutch). The Flemish Government, however, will evaluate the set of requirements every two years.

Building in Brussels

New-builds in the Brussels Region must conform to the following criteria from 1 January 2015:

• a net heating requirement of ≤ 15kWh/m² per year;
• an over-heating risk (inside temperature of more than 25°C) of
  < 5% of the time;
• a primary energy consumption of ≤ 45 kWh/m² per year;
• an air density of n50 ≤ 0.6 volumes/u (transitional system until 2018).

For buildings in the services sector – offices and schools – other requirements apply, which can be consulted on the Sustainable Buildings Guide website (of Leefmilieu Brussel (the Brussels Institute for Management of the Environment, website in French). Here, the criteria for an NZE building are taken a step further, but this is currently not determined by regulations. Brussels is therefore focusing primarily on energy efficiency and only subsequently on renewable energy.