In the current debate on the reform of the energy performance of buildings methodology (EPB), Agoria is asking for better utilisation of available European knowledge sources, such as the EPBD standards. But what knowledge do these standards actually contain? Below an overview of potential lessons from the standard for the general framework (NBN EN ISO 52000-1).
What is the NBN EN ISO 52000-1 standard?
NBN EN ISO 52000-1 is the standard for the overall framework for the determination of the energy performance of buildings. It is part of a package of around 90 standards aimed at standardising the determination methodology for the energy performance of buildings. Normally a standard can only contains normative provisions; therefore a supporting technical report EN ISO/TR 52000-2 was drawn up to also record the relevant non-normative knowledge that was generated during the development of the standard.
This contains an additional explanation of the reasoning behind a number of choices in the NBN EN ISO 52000-1, such as the design of the modular structure on which the standard is based. The NBN EN ISO 52000-1 comprises the following components; the overall framework, the preparatory steps, the determination of energy performance on the basis of measurements and calculations, the determination of the overall energy performance and output, the principles behind the determination and the zoning approach.
The principles behind the determination address, for example, the handling of recovered heat and building automation. The framework offered by NBN EN ISO 52000-1 is intended for both new buildings and major energy renovations (EPB, PEB) and existing buildings (EPC, la certification PEB, the EPB certificate).
Figuur 1: Schematische interpretatie van ISO 52000-1
EPBD standards and the energy performance of buildings in practice
The EPBD standards are a set of standards developed from M/343 around 2008 and revised from the mandate M/480 on behalf of the European Commission to support the implementation of the Energy Performance for Buildings Directive (EPBD). The objective of the standards is to bring together European best practices on the methodology for determining the energy performance of buildings and making them available to the member states.
The review focused on clarifying national and regional options. For example, Annex A and B were added to each EPBD standard; Annex A as a blank template to be filled in by member states and Annex B as a completed version of template A with (European) default values. In addition, a spreadsheet was developed for each EPB standard including calculation methods. The revised standards were largely published in 2017.
The next step is now to see how the information in the standards can be utilised to shape the optimisation of the EPB. The standards are not intended for one-on-one implementation, but rather as a source of knowledge; the Technical Committee has asked for practical experience with the implementation of the standards to be able to make any adjustments necessary for the applicability of the standards. Standards are regularly evaluated via the 'systematic review' procedure.
NBN EN ISO 52000-1 and the EPB; what knowledge could possibly help?
The discussions in the NBN EN ISO 52000-1 standard and EPB 2.0 overlap in a number of areas. The design of the EPBD standards is mainly aimed at recognizing patterns and trying to standardize variables in the calculation method. Below are a number of specific points that could be interesting in view of the discussion on the optimisation of the EPB in Belgium:
1. Actual measured vs. theoretically calculated consumption
One of the main points of discussion in the EPB reform (EPB 2.0) is the difference in the theoretically calculated consumption determined using the EPB methodology and the actual consumption measured in practice. The revised EPB aims to reduce this difference. The standard includes a number of aspects that contribute to the difference; the conditions (standard conditions for e.g. climate), the input (such as verification of the input data), the modelling (such as the impact of space use on the redistribution of heat), the human factor (such as deviation from anticipated building use) and peaks (not even hourly simulation can detect all peaks).
Furthermore, the standards contain a number of proposals for dealing with these aspects, such as the application of a method on an hourly basis in order to be able to model, for example, weather influences or interactions between technologies. In buildings with a low energy consumption, this becomes even more important. In the monthly method, this types of influences need to be statistically adjusted for. The monthly and hourly method are linked; the monthly method can be useful to verify the results of the hourly method and both methods can be used interchangeably in the calculation method. Agoria has initiated an exploratory study in January to see how the hourly method could be integrated into the EPB-PEB in Belgium.
2. Reference use when expressing energy performance in kWh
The requirements for the EPB can make use of a reference value, for example the 'E-peil'. The purpose of using a such a neutral unit as the measurement indicator is to avoid any confusion between the calculated energy performance of a building and the actual energy bill.
This energy bill is partly determined by the actual user profile of the building, while standardised user profiles are used during the design phase (see discussion point 1). The Energy Performance of Buildings Directive (EPBD) of 2018, however, requires that the numeric indicator of a building's primary energy consumption is expressed in kWh/m2 per year. As stated in the standards, a numerical indicator alone is not sufficient to determine the energy quality of a building.
Chapter 9 of the NBN EN ISO 52000-1 standard and EN ISO/TR 52000-2 technical report examine how standardisation can help to provide insight into the value of kWh/m2 per year as well as how this should be placed contextually. The possible approach for this is further described in the NBN ISO EN 52003-1 standard and the NBN EN ISO 52003-2 technical report. It discusses various approaches, such as sharing the value at a reference value and a proposal for the classification of the energy label classes (A to G).
3. Dealing with multi-zone approach
The inflexibility of zoning is one of the challenges in the current EPB; for example, placing a small local heating unit at a late stage of the design can require major adjustments in the modelling of the energy performance calculation. The standard proposes to integrate the zoning as a third step in the process (see figure 1). This step is part of the preparation for the calculation together with the determination of the internal usage conditions for each 'building category' or 'space category' (step 1) and the external climate conditions (step 2). The challenge of dividing a building into zones is to determine the correct number of zones and the exchange of data between different zones.
This exchange becomes more important in buildings with a high energy performance. The correct zoning depends, among other things, on the purpose of the calculation. The standard proposes to define zones based on 10 steps (see NBN EN ISO 52000-1, H11). A distinction is made between different types of zones, such as 'thermal zones' (e.g. residential areas) and 'service areas' (e.g. technical areas). The steps of the method can either be applied on the basis of the given parameters or be adapted per step by the Member State according to the template in Annex A.
4. Building automation and control systems
The revision of the EPBD (2018) has shown that building automation plays an important role in the energy performance of buildings. This also raises the question of how to best integrate this into the EPB through the role of the user and the indirect impact on energy efficiency. According to NBN EN ISO 52000-1, the most important role of building automation in the EPB is to find the right balance between energy efficiency and comfort.
The assessment of this is carried out on the basis of three criteria: control accuracy (CA), control function (CF) and control strategy. Control accuracy stands for the correspondence between the final control variable and the ideal value in the feedback control system. Control function is the extent to which the controller can perform a task. This is assessed on the basis of a categorisation of the degree of automation; D for non-energy efficient, C for standard, B for advanced, A for high-energy performance.
This classification has been developed for each technology. The control strategy is the extent to which the system can achieve its goal directly. A distinction is made, for example, between 'direct', 'based on time setting' or 'based on temperature'. Building automation and control systems are included in the calculation in the fourth step of the methodology for determining energy performance (see figure 1).
The next step: feedback from practice
The EPBD standards were revised in 2017 to make them more suitable for local application. The next step is the actual implementation of the standards. This practical experience can then be used to further finetuning of the standards. The EPB centre was set up in 2017 by ISSO and REHVA with the aim of providing support to Member States and other stakeholders in the further implementation of the EPBD standards. From this support, they will also be able to identify the issues that still need to be discussed within the development of the standards. Agoria has initiated a study to see how knowledge on the hourly based method could be integrated in the EPB in Belgium. This study will be carried out by the EPB centre and will be completed by the end of June 2019.
NBN EN ISO 52000-1 and EN ISO/TR 52000-2: Role of workgroup within the standardisation landscape
Standards NBN EN ISO 52000-1 and EN ISO/TR 52000-2 are part of the portfolio of standards managed by the European Standards Committee CEN/TC371. The aim of this committee is to develop and manage standards for the overall determination of the energy performance of buildings. The Committee currently manages 4 standards of which two were adopted in 2017. In addition, two standards concerning the primary energy factor (PEF) are currently being developed. The Belgian Mirror Committee E371 is the Belgian representation of the CEN committee with Agoria as its chairman. The NBN holds the secretariat. The activities of the Mirror Committee consist of voting, commenting and revising proposals for (European) standards. In addition, the Mirror Committee also has the possibility to develop a Belgian Annex or standard, for example to define local parameters.
Would you like more information about the standards or annexes? Members of Agoria can become a member of the mirror committee E371. For more information please contact Ludo Vanroy (firstname.lastname@example.org).