Nearly Zero Energy Buildings

The nearly Zero Energy Building “nZEB” is defined in the European Directive 2010/31/EU as « ‘nearly zero-energy building’ means a building that has a very high energy performance, as determined in accordance with Annex I. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby». 

Every European nation can define specific requirements in order to classify a building as nZEB. Member States shall draw up national plans for increasing the number of nearly zero-energy buildings. These national plans may include targets differentiated according to the category of building. They shall furthermore, following the leading example of the public sector, develop policies and take measures such as the setting of targets in order to stimulate the transformation of buildings that are refurbished into nearly zero-energy buildings.

Legislation

The European and international legislation is focusing on sustainability mainly through energy savings. The energy consumed for the operation of the buildings is a significant percentage of the total energy consumption. Reducing the energy needed for the buildings and the use of ecofriendly materials is a priority for the European Union and also for Greece.

According to the EPBD 2010/31/EU all new buildings by 12/31/2020 and after 12/31/2018 all new buildings occupied and owned by public authorities, should be nZEB. Member States shall take the necessary measures to ensure that new buildings meet the minimum energy performance requirements and that when existing buildings undergo major renovation, the energy performance of the building or the renovated part thereof is upgraded in order to meet minimum energy performance requirements (set in accordance with Article 4) in so far as this is technically, functionally and economically feasible.

Embodied Energy

The increasing need for sustainability in buildings and construction, will lead us in the near future to design buildings taking into consideration the total embodied energy in the life cycle of a building and not only the energy balance for its operation. 

The embodied energy in a life cycle of a building is the sum of energy consumed for the production of materials, construction, operation - maintenance, renovations, demolition and disposal of debris. The Embodied Energy is measured in energy units (MJ, GJ) per mass weight (kg) unit or surface (m2). The goal of sustainability is to minimize the energy consumed for human activities including the energy consumed to construct, operate and dispose buildings.

The Embodied Energy in a building can de distinguished in initial and repeated. The initial Embodied Energy is the energy required to product the components and materials of the building and the energy needed for the construction, while the repeated Embodied Energy is the energy spent for the operation and maintenance throughout the life cycle of the building. Selecting materials with low Embodied Energy reduces the initial Embodied Energy. The use of materials with long life cycle though they may have a larger initial Embodied Energy, may result in reduced total Embodied Energy throughout the life cycle. High specifications on energy efficiency result in low repeated Embodied Energy.