top of page

NZEB Nearly Zero Energy Building

NZEB stands for nearly zero energy building. The NZEB standard means that a building must have a very high energy performance. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources. This includes energy from renewable sources produced onsite or nearby.


When Does The NZEB Standard Begin?

The construction industry in Ireland is changing very fast. Keeping up with the new building regulations part L and NZEB is a task in itself. These changes will impact you as a construction worker, site manager, professional and building owner. The European Energy Performance of Buildings Directive Recast (EPBD) requires that all buildings acquired by public bodies should be NZEB compliant by 31st December 2018. It also states that all new buildings should be NZEB compliant by 31st December 2020.

If you work for the public authorities or build any public building, you have to meet NZEB standards by 31st December 2018. These could be schools, offices or residential developments. It states that all new buildings should be NZEB compliant by 31st December 2020. Any building completed after 31st December 2020 must achieve the NZEB standard irrespective of when they were started. A certificate of compliance with building regulations cannot be signed off and the building cannot be occupied until the NZEB standard is met.

Ireland carried out a cost optimal analysis in 2013 to define NZEB requirements. Part L of the building regulations defines the requirements in legislation.

Energy Graph.png

Domestic New Buildings

For all new builds it is proposed that NZEB will be equivalent to a 25% improvement in energy performance on the 2011 building regulations. Key changes to part L for NZEB compliance include a maximum energy performance coefficient of 0.3, a maximum carbon performance of 0.35 and a renewable energy ratio of 20%.

Domestic Major Renovation

It is proposed that major renovation of existing buildings is typically activated under the following circumstances where the work affects greater than 25% of the surface area of the existing dwelling:


  • External wall renovation, external or internal insulation

  • External wall and window renovation

  • External wall and roof renovation

  • External wall and floor renovation

  • New extension


Non-Domestic New Buildings

A 60% improvement in energy performance for all new builds on the 2008 building regulations is required. This means an improved in energy performance for the fabric, services and lighting specification. It also introduces a mandatory requirement for renewable sources. The renewable sources must in general provide 20% of the primary energy use. However there is flexibility where the building is more energy efficient than the regulations. This typically corresponds to an A3 building energy rating.

Non-Domestic Major Renovation

Major renovation for existing buildings under EPBD is where more than 25% of the surface area of the building envelope undergoes renovation. This will require that the building is brought up to cost optimal level, which is defined in the building regulations as:

  • Upgrading heating systems more than 15 years old

  • Upgrading cooling and ventilation systems more than 15 years old

  • Upgrading lighting more than 15 years old


Benefits of NZEB

All new homes will be nearly zero energy buildings (NZEB) and will have a typical building energy rating (BER) of A2. This is compared with the current A3 rating for new builds. New homes will be 70% more energy efficient and will emit 70% less carbon dioxide than 2005 performance levels. A typical A-rated, 3 bedroom, semi-detached house is likely to be approximately €800 per annum cheaper to heat than a similar house built before 2005. Existing dwellings undergoing major renovations will be required to achieve a BER of B2 or equivalent.

The new regulations are expected to result in reduced fuel bills for new or majorly renovated dwellings compared to bills for existing dwellings. As a result of improved indoor air quality, better performing buildings provide higher comfort levels and wellbeing for their occupants and improve health.

Health benefits have been reported as the most important benefit of energy efficiency improvements in residential buildings including low income households. Initial reports from occupants of NZEB homes in Ireland are reporting the health benefits of improved comfort and indoor air quality. CSO statistics also show that NZEB regulations are eliminating the use of solid fuel in new dwellings and also benefit from outdoor air quality.

Approximately 40% of Ireland’s energy related emissions are from buildings. Under the current regulations, a typical new dwelling is built to an A3 BER standard. The NZEB requirements will result in a typical BER of A2, which represents a 70% improvement in carbon emission levels on the emission levels of buildings from 2005.

How Difficult Is It To Achieve NZEB?

There have been an number of residential developments achieving these standards and because the building regulations part L have been progressing towards NZEB, a 20% improvement on the 2011 part L revisions will bring you in line with NZEB. Further information can be found on the Department of Housing, Planning and Local Government website and the Sustainable Energy Authority of Ireland website below:

Nearly zero energy buildings NZEB future

Nearly zero energy building standard

NZEB in domestic buildings


NZEB and Hession Energy

Hession Energy carries out the NZEB calculation along with part L 2019. Please contact us for further information and we will be more than happy to help you.

bottom of page