What is NZEB, how to build a near-zero energy building

NZEB is a building efficiency standard. From 2021, all new buildings - houses, blocks of flats, schools, nurseries, hospitals, sports halls and concert halls - must meet this standard. NZEB is short for near zero energy building which means near-zero energy building. The concept originated in the European Community to reduce energy consumption in residential buildings. EU Directive 31/2010 obliges all Member States to implement measures to reduce energy consumption from 31 December 2018 for new state-run buildings and 31 December 2020 for new private buildings.

Law 101/2020 on the energy performance of buildings is what makes the standard mandatory in Romania. As a result, the design and construction of new buildings must be done in such a way that energy consumption for maintenance (heat, hot water, ventilation, lighting) is very low, while comfort remains high. The publication in the Official Journal of Methodology for calculating the energy performance of buildingsThe new European Commission's "European Design Guide", due in January 2023, comes with clear calculation methods for architects, designers and builders. There are now all the elements needed to correctly build energy-efficient homes to NZEB standard.

What is NZEB

According to Law 101/2020, the definition of a building constructed to NZEB standard is "building with very high energy performance, where the energy requirement for energy performance is close to zero or very low and is covered in this way: (a) in a proportion of at least 30%, with energy from renewable sources, including energy from renewable sources produced on-site or nearby, within a radius of 30 km from the GPS coordinates of the building, starting in 2021; (b) the minimum proportions of energy from renewable sources, including energy from renewable sources produced on-site or nearby, within a radius of 30 km from the GPS coordinates of the building, for the periods 2031-2040, 2041-2050 and after 2051, shall be determined by Government decision"

The European Union has recommended increasing the share of renewable energy to 80% after 2050, with each country setting the level for each period. This is what point b) refers to. The recent energy crisis has led to an acceleration of this plan at European level, with the new target of 80% renewable energy to be reached by 2040.

The standard for near-zero energy buildings was known as nZEB. The capitalisation at the beginning, i.e. NZEB (net zero energy building), used to define buildings that do not use conventional energy or if they do, they recover all of it. With the publication of the Calculation Methodology, the NZEB standard for near-zero energy buildings has been formalised in Romania.

Which buildings must meet the NZEB standard

All residential, office, educational, sports, hospital or performance buildings, i.e. all newly constructed buildings for people where heating, hot water and lighting are needed. Buildings undergoing major renovations must also meet the NZEB standard. Major refurbishment means intervention worth more than 25% of the value of the building. Exceptions to the NZEB standard are historical monuments, places of worship and the execution of projects approved before the law was published.

Everyone designing or constructing new buildings should be familiar with the regulations of the standard. Without proper energy compliance, the project will not be able to receive planning permission and a building that does not meet the criteria of the NZEB standard will not be able to be approved.

Clarifications on the methodology

Although the law was published in 2020, the lack of methodology for calculating and applying the various parameters (insulation thickness, heat transfer coefficient, air exchanges, etc.) created a lot of confusion, left room for interpretation and so ways were found to get around it. The emergence of Methodology for calculating the energy performance of buildings clarifies things for architects, designers and builders as well as for beneficiaries. It is a comprehensive document that deals with all aspects of the building: envelope, type and fitting of windows, installations used, necessary documents, comfort.

The main requirements for NZEB residential buildings specified in the methodologies are:

• an annual maintenance energy consumption at a certain level. For example, for residential buildings, this should be between 120.1 kWh/m² and 147.9 kWh/m² per year. The difference is due to construction in different climatic zones, with heating requirements depending on how cold the zone is);
• the maximum greenhouse gas emission value. For residential buildings, this should be between 14.7 kg/m² and 19.9 kg/m² annually, also differentiated by climate zones;
• 30% production of the energy needed from renewable sources.

A summary of the methodology made by Marius Șoflete, with explanations and clarifications, can be found at here.

How to build to achieve the NZEB standard

In Romania, the most important energy consumer is the building sector, whether private or public. Heat consumption for heating buildings and domestic hot water accounts for about 70% of total energy consumption. In 2020, the annual energy consumption of residential buildings was in the range 180-400 kWh/m². The time has come to build better and more responsibly to change this.

The energy consumption of a building depends on the insulation systems, the performance level of the windows, how economical the lighting system is, how efficient the heating, ventilation or ventilation systems are. The choice of these systems and their correct installation determines the energy performance of the building. The energy configuration is made at the design stage, according to the annual energy consumption to be achieved, i.e. that required by the NZEB standard.

Ensuring a continuous and sufficiently thick thermal envelope, high performance windows with low heat transfer coefficient, both glass and frame, elimination of thermal bridges, uncontrolled air exchange with the outside, heat recovery ventilation system, economic lighting, comfort level are important key factors in achieving the NZEB standard.

What are the advantages of building to NZEB standard for the beneficiary?

The first big advantage is the significant decrease in energy consumption. We have seen this year what an energy crisis means. Reducing the energy needed to run the building means very low maintenance bills.

Replacing part of the energy consumed with energy from renewable sources is another advantage. Reducing fossil fuel consumption means less pollution and cleaner air.

Always fresh air and quality lighting positively influence the quality of life of residents. Studies have shown that mental well-being is also much better in such an environment.

Why it is good that Romania is implementing this European directive

The European Union Directive 31/2010 has obliged us to implement the NZEB standard and make building efficiency programmes. That was our good fortune. Now we have no choice but to build more economical, comfortable and healthy homes. The energy crisis generated by the border conflict has shown us how risky energy dependency is. The lower our consumption and the more varied our energy sources, the less we are affected by global price fluctuations and raw material crises caused by armed conflict or other events.

nZEB Roadshow caravan in Iasi and especially nZEB Week in Cluj have shown us how effervescent the construction industry has become. The NZEB standard has taken the industry to a new level and we all stand to gain.