The European Energy Performance of Buildings Directive (EPBD 2010/31/EU) requires all new buildings to be nearly zero-energy (NZE) by 2021. This goal was set out in the Energy Decree in 2014. In 2015, the Flemish Energy Agency (Vlaams Energieagentschap; the ‘VEA’) launched the process to prepare the fourth EPB review. The fourth review of the energy performance regulations naturally examines the experiences over the nearly ten years of EPB requirements since 2006, but it primarily focuses on the objective of making all new buildings nearly zero-energy (NZE) by 2021. In the 2015 EPB evaluation, the VEA examined whether the various aspects of energy performance regulations (requirements, methodology, procedures) were ready for NZE buildings. This was based on findings from several policy preparation studies and on consultation with the sector.

Gradually ramping up EPB requirements will ensure that new buildings become increasingly energy efficient. The process will use increasingly innovative technology and materials. Because requirements are being strengthened, the sector will devote more attention to calculating energy performance figures for buildings. A refined calculation method is required for adequate and detailed energy performance calculations for NZE buildings.

The 2018 method amendments are now being implemented. This draft amending decree also contains a number of technical adjustments to the EPB calculation methods. The main adjustments concern the change in the generation efficiency of space heating and the amendment to the method for incorporating solar water heaters into the calculations.

For the generation efficiency of space heating, the amendments make it possible to incorporate data from the European Ecodesign regulation into the EPB calculation. For manufacturers of generators, this offers the benefit that they are not required to conduct special product testing specifically for the Belgian market. The input data is available from European requirements.

The amended method for incorporating solar water heaters into calculations makes it possible to consider product data, instead of a fixed flat-rate efficiency figure. This also improves the incorporation of higher performing systems into the calculations, resulting in a lower E-level.

- Draft Decree of the Flemish Government amending the Energy Decree of
19 November 2010, concerning amendments to various provisions on energy
performance regulations;

- Annex 1 (replacing Annex V – EPW calculation method);

- Annex 2 (replacing Annex VI – EPN method); and

- Annex 3 (replacing Annex VIII – Measures for thermal bridges).

Article 1 (concerns amendments to Annex V)

The requirements that new buildings must meet in the area of energy performance are becoming increasingly stringent. More and more innovative technologies and materials are being used to meet these increasingly stringent requirements. As a result, the calculation method must also be refined for proper and accurate incorporation of these new materials and technologies.

Adjustments to the calculation method are developed within the EPB platform. This is a consultation platform between the three regions, which has been supported by a consortium of scientific partners since 2014. Based on several studies completed by the EPB consortium in 2016, amendments are being applied to the calculation method set out in Annex V (EPW method). The summary below explains the main amendments:

- Revision of the method for calculating the ventilation flow rate, used to determine the overheating indicator in cases of ventilation with manually opening parts: in practice, the existing method that incorporates the surface area and the intrusion risk from the opening parts (explained in further detail in a guideline) has proved to cause a great deal of uncertainty. This method is now replaced with a method that takes into account the potential of each energy sector for intensive ventilation. The intensive ventilation potential is determined based on a decision tree that identifies the included impact criteria.

- Revision of the method for generation efficiency of central heating systems: the existing method for generation efficiency is now replaced by a method based on Ecodesign data. The calculation method is now also expanded to cover generators that were not included in the existing calculation method, but that were in fact included in Ecodesign.

- Revision of the method for electricity production by photovoltaic solar power systems. Several new terms are now incorporated into the reduction factor, which is current established at 0.75, to take into account panel technology (monocrystalline or polycrystalline versus thin-film), inverter type (with or without galvanic isolation) and the method of integrating the panels into the isolation barrier (built-in or surface-mounted). Overall, the reduction factor is actually higher now, in order to better line up with actual average performance figures for PV panels in Flanders.

- Revision of the method for output from solar thermal systems. The current method poses some problems. For instance, it is not possible to incorporate component properties. Moreover, in some cases, the results for combined systems do not line up at all with expectations. The new method, which is based on standard prEN15316-4-3:2014 and Ecodesign to the greatest extent possible, resolves this error and allows the detailed incorporation of factors such as collector properties, storage tanks and pumps. If specific information is not available, the simplified calculation is always available as a last resort.

Some other minor amendments are made to Annex V to clarify the text or harmonise the various annexes.

Article 2 (on amendments to Annex VI)

Based on several studies completed by the EPB consortium in 2016, amendments are being applied to the calculation method from Annex VI (EPN method). The summary below explains the main amendment:

- Adjustment to the new method for generation efficiency. For the generation efficiency of central heating systems, please refer to the updated calculation method for EPW units (Annex V); see Article 5. Based on these changes, text and formula adjustments are being applied to Annex VI.

Article 3 (on amendments to Annex VIII)

Based on a study completed by the EPB consortium in 2016, Annex VIII (thermal bridge annex) is being amended. The following changes are applied to it:

- Updates for introduction of the S-level: thermal bridges must be incorporated at the level of the EPB unit (no longer at the level of the K-level). All references to the K-level are now removed.

- A new provision provides a statutory basis for manufacturers, who meet the conditions, to make Ψ values available as a ‘default value’ to reporters.

- The text from Annex V (EPW method), stating that the thermal bridge supplement in option C should not be incorporated into cooling requirements calculations, is now moved to Annex VIII.

Article 4 (on amendments to Annex IX)

The Amending Decree of 13 January 2017 added a point 1/3 that indicates which flow rate can be applied for a flow opening. A provision was taken from non-residential ventilation. However, the option to dimension a flow opening for a pressure difference of 10 Pa was incorrectly adopted as well. This would result in smaller flow openings, which is not desirable for residential ventilation because the flow rate capacities for flow openings are already almost always less than the required flow rates for the spaces. In addition, smaller flow openings would result in higher cumulative pressure differences. This would require more powerful fans, which in turn could result in increased infiltration (for system C) and less actual supply to the dry spaces. This change explicitly removes the option to dimension a flow opening in residential buildings for a pressure difference of 10 Pa.

Point 1(c) of this Annex explicitly cites several points from ventilation standard NBN D50-001 as recommendations, such as the minimum height of 1.8 m for installation of a supply facility. Point 2(c) of this Annex cites this same minimum height as a requirement. Thus, this is contradictory. Removal of point 2(c) eliminates the contradiction and makes the minimum height of 1.8 m effectively a recommendation, as was always the intent.

Article 5 (concerns amendments to Annex XII)

An EPB platform study on the Ecodesign legislation prompted amendment of Annex V to the Energy Decree of 19 November 2010 (see Article 5). The amendments also necessitate adjustments to Annex XII to the Energy Decree of 19 November 2010. After all, for electric heat pumps, this refers to the term SPF, which the amendment now changes to ηgen,heat. The table that sets requirements on different types of heat pumps is now expanded with several new types to clarify that they are not subject to requirements.

In addition, the default value for electric heat pumps is now removed because this was redundant due to the reference to Annex V to the Energy Decree of 19 November 2010 in the same Section. The default value for the part-load efficiency for boilers is now removed because it contains an anomaly with respect to the table in Annex V to the Energy Decree of 19 November 2010, to which it referred.

Moreover, the distinction between different types of boilers in the calculation of the part-load efficiency is now clarified.