NZEB requirements and energy label C as standard

Dec 13, 2022

Time is running out… Now is the time to take impactful steps towards a climate-neutral built environment. Office buildings in the future must meet stricter energy requirements. The nZEB requirements have been in force for new office buildings since 1 January 2021. In addition, as of January 1, 2023, existing office buildings must have at least Energy Label C.

Solarix nZEB requirements

In the built environment, we see that many buildings still do not meet energy-efficient standards, neither the nZEB requirements in new buildings nor the minimum energy label C in existing buildings. For example, the NOS recently conducted research into government buildings that will not meet the minimum Energy Label C. For new construction, a nZEB calculation is required to demonstrate that you meet the nZEB requirements. Here it turns out to be difficult to include the correct input for solar panels, for example

The new energy requirements are great steps that contribute to the acceleration of the energy transition, but what should project developers and architects pay attention to? What should you consider when making a nZEB calculation to measure your energy performance? When does Energy Label C apply? What can Solarix do to meet these new energy requirements?

Read up quickly with our blog and start with the energy calculation for your project.

What is the difference between nZEB and Energy label C?

First of all, it is good to make a distinction between the nZEB requirements for new construction and Energy Label C for existing buildings.

nZEB stands for ‘nearly Zero Energy Building and is a set of requirements based on improving the energy performance of European buildings. Since January 1, 2021, it has already been established by law that all new construction, both residential and non-residential construction, must meet these BENG requirements in order to obtain a permit. This is often tested for the first time in a preliminary design. The nZEB requirements have been laid down nationally, but can be tightened by municipalities or during tenders

Since 1 January 2016, it has been mandatory for office buildings to have an energy label. Energy label C is an additional measure for existing buildings and will be mandatory for office buildings from 1 January 2023. From then on, office buildings may have “a primary fossil energy consumption of a maximum of 225 kWh per m2 per year”.

The Human Environment and Transport Inspectorate (ILT) checks whether offices comply with the law. The Inspectorate is already issuing hefty fines for the lack of an energy label when selling or renting business premises. Does an existing office building not have an Energy Label C after the turn of the year? Then it may no longer be used as an office!

Solarix nZEB requirements
New generation of solar panels: Optopper Solarix

Indications of the nZEB requirements

According to RVO, the nZEB requirements are based on the principle of Trias Energetica: first limit energy demand, then obtain energy as much as possible from renewable sources and use fossil energy sources efficiently for the rest.

The energy performance at nZEB is therefore determined on the basis of these three individual requirements:

nZEB 1: Maximum energy requirement in kWh/m² usable area per year
With this value it is important, among other things, to look at the quality of the building envelope. In other words, an office building needs a good thermal envelope so that as little heating or cooling as possible is required. Look not only at roof and floor insulation, but also at the potential of an insulating facade in this regard.

nZEB 2: Maximum primary fossil energy consumption in kWh/m² usable area per year
For this, the energy used in a building, for example from installations, must be kept as low as possible with energy-efficient solutions and simply smart energy use.

This sets a requirement for the maximum amount of primary fossil fuel required for heating, cooling, hot tap water and ventilation of an office building. In utility buildings, lighting and humidification/dehumidification are added to this. Efficiency and type of installations and systems within a building and the application of renewable energy play an important role in this.

If a building – for example with PV panels such as solar panels – generates its own energy, the primary fossil energy consumption may be reduced by the amount of energy generated.

NZEB 3: Renewable energy in %
Is energy still needed? Then you have to generate this renewable for a certain percentage, such as with solar panels. Different percentages apply for each building type.

The most important of this requirement is actually the sum of the primary fossil energy consumption part plus the renewable energy part. In this, the amount of renewable energy is divided by the total energy consumption. However, the renewable energy must be generated in, on or at the building!

If we translate these indications into a number of practical facilities that influence the NZEB requirements, then sustainability solutions such as:

  • Replace all lighting with LED lighting.
  • Replacing conventional boilers with high-efficiency boilers.
  • Replacing glass with HR++ glass.
  • Insulating the roofs, facades and floors.
  • Installing heat pumps (water/water, air/water, ventilation air/water and booster).
  • Installation of solar water heaters.
  • Placing sunshades.
  • Placing solar panels on the roof
  • Placing solar panels on the facade.
  • Installing a green roof.
Solarix nZEB requirements

How do office buildings meet the nZEB requirements or Energy Label C?

Office buildings are getting taller and the number of square meters of roof surface for traditional PV panels is limited in order to meet the energy demand for stricter laws and regulations such as the nZEB requirements and energy labels.

To make existing and future office buildings more inspiring and sustainable, design facade PV panels can be used and even combined with non-active panels made of other materials.

Placing PV panels on the facade, or facade solar panels, is therefore one of the most attractive sustainability solutions. This allows a new office building to generate renewable energy and thus meet the nZEB 3 value

With existing office buildings, energy can be generated by means of this facade solar panels (PV facade), which means that less kWh of primary fossil energy is required per m2. As a result, the standard of the Energy Label C can be achieved.

Help with the nZEB calculation

An actual nZEB calculation is quite complicated as you can read in the indications. We believe that you can use the necessary support in this! Discover our tips:


It is important for a nZEB calculation to include the correct starting points. Solarix can support this by means of the Solarcheck in which the potential energy generation of a building is calculated. For example, we provide essential information for the nZEB calculation, such as the number of m2 of PV panels, orientation(s), Wp per m2 and ventilation.


For engineering, we even go a step further to optimize the energy performance of the solar facade with a SolarScan, a follow-up step to the SolarCheck. This allows us to provide the client with targeted and extensive advice on the application possibilities of the Solarix panels in the relevant project.

Together with our building physics and construction engineering experts, we assess the design options and detailing. In addition, we conduct an extensive solar study including shadow. The result is architectural advice in which we can also make a good cost indication and thus also calculate the payback period.

With a SolarScan we actually compare the nZEB wishes and possibilities for the facade and we optimize the effectiveness of the energy yield with the sizes and colors of our design PV panels.

Solarix nZEB requirements
Solarix nZEB requirements
Advice from an energy consultancy

Do you opt for an energy consultancy? Then make sure that the correct input for facade panels is used for the nZEB, such as the Wp per m2 instead of the Wp per panel. The calculation is really different here than for roof panels. We often see that it is wrongly assumed that too high capacities per m2 are used for traditional roof panels.

With custom-made and aesthetically colored panels, the capacities are relatively lower, but they have an aesthetic added value that the traditional panel lacks.

Start by calculating the nZEB

We see an increasing demand for sustainability solutions for office buildings now that the nZEB requirements and energy labels are becoming stricter.

It is clear that the integration of solar panels in the facades is emerging as a very cost-effective option to achieve energy neutrality for both the nZEB requirements in new construction and Energy Label C in the existing construction of office buildings. Often, only PV on roofs is not enough.

At Solarix, we believe that PV solutions for office buildings should not lead to a dark glass city without identity and beauty. We therefore produce design solar panel facades that work efficiently and look aesthetically pleasing.

Curious about the possibilities? Start your nZEB calculation and start with the SolarCheck!

How much energy does your project generate?

In our non-binding Solarix SolarCheck we calculate how much energy your facade can consume based on satellite data and 3d project drawings.

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