The public consultation on the proposal for the Belgian Annex to the standard for calculating the heat load for spaces (EN 12831-1) closed on the 15th of July. On October 3rd, the E228 "Heating systems in buildings" working group will meet to discuss the feedback on the proposal.

In the article of 6 December 2018, we announced the public consultation on the proposal for the Belgian Annex to the standard for calculating the heat load for spaces (EN 12831-1). This consultation closed on the 15th of July. On October 3rd, the E228 "Heating systems in buildings" working group will meet to discuss the feedback on the proposal. 

A brief summary of the developments so far

In January 2018, a working group was set up to draft the Belgian Annex to the EPBD standard for calculating the thermal load of spaces. The reason for the proposal was the idea that the methodology proposed in the European standard is too complex to be useable by smaller installers without access to software. This could be particularly problematic in the initial estimation of the dimensioning of heating or cooling systems. The possibility of adding a national annex to all standards was included with the revision of the EPBD standards in 2017. The working group worked on a textual proposal for the Belgian Annex in a number of meetings on the basis of a submitted proposal by one of the participating experts. Finally consensus was reached to allow the draft to move on to the next phase: the public consultation. This phase allows all stakeholders to comment on the proposal. The comments that have emerged from this public consultation will be discussed and integrated in de text proposal for the Annex during the next working group meeting on the 3rd of October 2019. As the feedback includes technical comments, the text proposal might has to be (re)submitted to the Belgian Mirror Committee SA/E228 for approval. The Annex will be finalized with the official publication of the Annex in the Belgian Official Gazette. 

What is the heat load standard for spaces (EN 12831-1)?

The EN 12831-1 provides options for calculating the heat load of spaces (also known as the heat loss calculation). This is the calculation used by installers to determine the dimensioning of the heating system. This is done on the basis of the calculation of the maximum heat output required per hour for a heat generator to reach or maintain an internal design temperature at a certain outside air temperature. Within the EPB policy framework, the standard forms the basis for the standard calculation sheet that is made available by the WTCB to determine the departure and return temperatures of a heating (or cooling) system. With this calculation sheet, the capability of a designed delivery system to achieve a certain level of comfort can be demonstrated; the spreadsheet is considered a validated supporting document in the dimensioning note required in Flanders. Potential alternatives are the use of default values or other documentation, but these are not always sufficient to meet the requirements.

For more information about the heat load standard for rooms, click here

Important discussion points for the Belgian Annex

The risk of overdimensioning when applying the standard was one of the main topics in the discussions on the Belgian Annex. Overdimensioning can be caused, among other things, by the use of parameters that are ‘too safe’ or default values. The method for the calculation of losses (e.g. infiltration losses, ventilation losses) remains an important point of attention.  The values of airtightness, which can be further reduced in the coming years by innovations in building technology, also continue to be a point of discussion. Other aspects that can influence overdimensioning are the inclusion of the heat-up power in combination with too low minimum temperature values. In the proposal, the heating capacity can therefore be included optionally in the calculation and the applied climate data was updated. One outstanding issue raised during the working group discussions was how best to include ventilation in the calculation. This needs to be further investigated in order to arrive at a concrete proposal. 

Also on the agenda October 3rd: an update of the SmartPower project

During the meeting on the 3rd of October a short update will be given on the SmartPower project. This is a pre-normative study currently being carried out by the WTCB. A pre-normative research is a study financed by the Federal Public Service (FPS) Economy to provide technical and scientific support for the development of standards. One of the objectives of the SmartPower study is to draw up a smart metering protocol on the basis of which the required power in existing buildings can be determined quickly. During the meeting on October 3rd, a brief state of affairs of the project will be given by the project leader of the WTCB. 

Update of the Belgian Annex to the heat load standard for domestic hot water (EN 12831-3)

A working group for the Belgian Annex for calculating the heat demand for domestic hot water (EN 12831-3) was launched at the same time as the working group for the Belgian Annex for calculating the heat load for spaces. The standard on the calculation of the heat demand for domestic hot water is used for the dimensioning of domestic hot water installations. The reason for the Belgian Annex is that there would be a need for further differentiation within the profile included in the European standard. This includes for example different household compositions, but also profiles for sports halls, hospitals, schools, etc. The WTCB is currently working on research on the basis of which they will make a first text proposal for the Belgian Annex. In anticipation of this proposal, the working group has been temporarily put on hold. The next meeting will be scheduled as soon as a text proposal is available. 

EN 12831-1 and EN 12831-3: Role of workgroup within the standardisation landscape

The standards EN 12831-1 and EN 12831-3 are part of the portfolio of standards managed by the European Committee for Standardisation CEN/TC228. This commission is focused on the development and maintenance of standards for heating systems and water based cooling systems. Currently the committee manages around 30 (EPBD) standards, of which the majority was approved in 2017. The Belgian Mirror Committee SA/E228 is the Belgian representation of the CEN committee. Sirris-Agoria is its sector operator. The activities of the Mirror Committee consist of voting, commenting and revising the proposals for (European) standards. In addition the Mirror Committee has the possibility to develop a Belgian standard or Annex to for example define local parameters. The two working groups that are currently active within the Belgian Mirror Committee are aimed at the development of Annexes for the European '12831' standards. The standards describe the calculation methodology to determine the heat load of buildings for spaces (EN 12831-1) and domestic hot water (EN 12831-3). For more general information on the EPBD-standards, click here.

 Would you like more information about the standards or annexes? Members of Agoria may become join the mirror committee SA/E228 as experts. Contact Ludo Vanroy ( for more information.