Currently the energy performance of a building is determined on a monthly basis in Belgium. The choice for either a monthly or hourly methodology has an impact on the accuracy of the determination of the energy performance of a building. The application of the hourly method offers a possible solution to simplify the integration of innovation in building technology in the EPB.


In 2019 the EPB-Center carried out a study at the request of Agoria into the possibilities of having the Belgian energy performance methodology for new buildings or equal calculate on an hourly basis.

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Combination of the monthly and hourly method

The study was based on the NBN EN ISO 52016-1 standard, one of the EPB standards, which describes, among other things, a methodology to determine the energy demand for the heating and cooling of buildings. For building technologies in particular, the level of detail can have a significant impact on the accuracy of the final energy performance. As the energy performance of a building becomes higher, this impact becomes more significant. Most energy performance methodologies work currently on a monthly basis. The NBN EN ISO 52016-1 standard therefore offers the possibility to combine the monthly and hourly method in order to simplify the implementation. A number of European countries have already started to take steps to realise this.

Approaches to combining multiple zones

Zoning is an essential part of the determination of the energy performance of a building. A frequently asked question about the hourly method is how the results per zone can be combined; by adding them up or by using thermal coupling. This last option means that the heat exchange between rooms is also taken into account. A disadvantage of this approach is that the required temperatures of the adjacent rooms are not always easy to determine. In addition, the impact on the calculation is negligible; therefore, even in simulation programs, zones are linked separately and not thermally. In the end it comes down to roughly the same results. An add-up of the results seems therefore to be the most logical choice.

Role in the simplification of the EPB methodology

In the hourly method, the behaviour of building technology in the calculation is modelled via algorithms instead of the correction factors used in the monthly method. Correction factors must be laid down in the regulations, which can make the inclusion of innovative products a time-intensive process. By using the hourly method, the determination of separate correction factors is in principle no longer necessary. This is not because correction factors are no longer applicable, but because their effect is negligible. Integration of the hourly method could therefore lead to a reduction in the time needed for the integration of innovative products in EPB.

Next steps

The results of the study show that an application of the hourly method can certainly result in a lower resulting energy requirement. However, a comparison with the Belgian EPB methodology still needs to be made in order to assess the impact on the energy performance. A difficulty here is to assess to what extent the parameters from both calculations match. Therefore, the next step is to examine to what extent it is possible to develop a number of business cases in which both methodologies can be compared.

More information? Click here for a full description of the results of the study.