One Building, One Evidence Base

Keywords: openBEP4EU; EPBD; EPC; SRI; BACS; EN ISO 52000; technical building systems; building performance assessment; compliance

EPBD implementation now needs a more coherent technical basis for EPCs, SRI and BACS compliance. The EU LIFE project “openBEP4EU” offers a practical way to test how standards-based calculation tools, checklists and building evidence can support several assessments without turning them into a single procedure.

A practical implementation problem

The revised Energy Performance of Buildings Directive increases the number of places where reliable building information is needed. Energy Performance Certificates remain the familiar public reference for building energy performance. The Smart Readiness Indicator adds a framework for assessing how well a building can adapt its operation to users, technical needs and the energy system. Building Automation and Control Systems requirements create a need to verify that certain buildings have the minimum automation and control capabilities required by the EPBD.

These instruments have different purposes, but they often look at the same building and at many of the same technical systems. An assessor may need information on heating, cooling, ventilation, lighting, controls, metering, renewables, electric vehicle charging or system operation. A building owner may be asked to provide documentation for an EPC, an SRI assessment, a BACS compliance check, a technical system inspection or a renovation plan.

This is where openBEP4EU becomes relevant. The project is developing an open-source toolbox and shared calculation engine for more harmonised EPC and SRI assessment. Its primary focus is the demonstration of the use of a selected set of EN/ ISO EPB standards for energy performance assessment. At the same time, the project raises a wider implementation question: once building information is structured for one assessment, how much of it can be reused safely for another?

The answer will not be the same for every Member State or every building type. National authorities remain responsible for their own EPC systems, SRI rollout choices and compliance procedures. A more consistent technical basis can nevertheless reduce duplication, make results easier to compare and help the market understand how the different EPBD instruments relate to each other.

Figure 1. A shared building evidence base can support several distinct EPBD assessment, compliance and planning processes.

Why EPC and SRI need a common language

EPCs and the SRI answer different questions. An EPC gives a calculated view of energy performance. The SRI assesses smart-ready services across nine technical domains: heating, cooling, domestic hot water, ventilation, lighting, dynamic building envelope, electricity, electric vehicle charging, and monitoring and control.

In practice, both assessments depend on a clear description of the building’s technical systems. What systems are installed? How are they controlled? Is metering available? Are renewable energy systems present? Can the building adapt operation to occupancy, user needs or external signals? Which services are manual, automated or connected? A common technical language helps avoid inconsistent answers. The set of CEN and ISO Energy Performance of Buildings (EPB) standards (with its core: the family of EN ISO 52000 standards) provides the common technical framework for assessing the energy performance of buildings in Europe and globally. EN ISO 52120-1 gives a way to describe the contribution of building automation, controls and technical building management to energy performance. Used together, these standards can help building professionals move from general claims about “smart” buildings to functions that can be described, calculated and checked.

For openBEP4EU, this is not just a theoretical point. A standards-based calculation environment can make assumptions, inputs and outputs more visible. It can also help show which building data is relevant only for EPC calculation, which information may also support SRI assessment, and where additional evidence is needed.

Bringing BACS into the same workflow

The EPBD sets minimum capability requirements for Building Automation and Control Systems in certain buildings. These requirements concern what the installed systems can do: continuously monitor, log and analyse energy use and allow adjustment; benchmark energy efficiency, detect losses and inform the person responsible for the building; communicate with connected technical building systems and interoperate across technologies, devices and manufacturers; and monitor indoor environmental quality.

Compliance with these requirements needs to be assessed in a practical and consistent way. That means looking beyond the presence of equipment and checking whether the required functions are actually available and usable. A BACS compliance checklist can help structure this process by linking legal requirements to evidence that owners, installers, assessors or inspectors can provide.

The connection with SRI is useful because both processes look at technical building system capabilities. The BACS compliance check asks whether minimum required capabilities are in place. The SRI looks more broadly at the smart readiness of services across the building. Keeping the distinction clear is important, but the evidence should not have to be collected from scratch each time. In an openBEP4EU context, integrating a minimum BACS requirements checklist into an SRI calculation environment can therefore support a more coherent workflow. It can help assessors understand when BACS evidence is relevant to SRI assessment, where the same information can be reused, and where the SRI method requires additional service-level information.

Figure 2. Evidence used to verify minimum BACS capabilities can support the assessment of smart-ready services across the nine SRI technical domains. Highlighting indicates illustrative areas of overlap, not an exhaustive mapping; the procedures retain distinct purposes and methodologies.

The role of the calculation engine

The openBEP4EU calculation engine offers a practical place to test this integration. For BACS, the question is how specific automation and control functions are represented in the calculation logic or supporting assessment workflow. Some functions may be directly reflected in an EPB calculation parameter. Others may influence assumptions indirectly. Some may not yet be represented in the current engine.

Documenting this properly matters. A BACS Function Coverage Register aligned with EN ISO 52120-1 function identifiers can help show the relationship between BACS functions, EPB modules and kernel parameters. It can also make clear whether a function is directly quantified, represented through an explicit mapping or proxy, or not yet quantified. This avoids overstating what the tool can do, while giving project partners and future users a transparent roadmap for improvement.

The same traceability logic can apply to the minimum BACS requirements checklist. Instead of treating the checklist as a separate document outside the assessment workflow, the tool can help structure the evidence and show how it relates to SRI assessment and EPC data. The result is not an automatic compliance decision. Professional judgement, national rules and proper verification remain essential. The benefit is traceability: a clearer route from technical function to evidence, assessment input and output.

Figure 3. The proposed coverage process traces BACS functions to the relevant EPB calculation route and assigns one of three transparent kernel-coverage statuses: directly quantified, represented through mapping or not yet quantified.

Less duplication for owners and assessors

For building owners and managers, the value of a shared evidence base is practical. Owners should not need to recreate the same technical file for every assessment. System descriptions, rated outputs, control functions, metering points, commissioning records, EPC calculation inputs, SRI service data, technical system inspection records and BACS checklist evidence may all sit in different places today. A better workflow would make it easier to collect, verify and reuse the relevant parts.

For assessors, this can reduce administrative work and make inconsistencies more visible. If the EPC file describes one system configuration and the SRI assessment assumes another, the difference should be easier to detect. If a BACS checklist confirms that certain monitoring or control functions are present, that information should be available where it is relevant for the SRI assessment, without replacing the SRI method itself.

For public authorities, structured data can support quality control and clearer guidance. It can help identify missing evidence, inconsistent assumptions or recurring implementation issues. This is especially important as EPBD implementation moves from legal transposition into everyday practice, where assessors, installers, owners and facility managers need procedures that are robust but workable.

Figure 4. A structured and verified building evidence base can support several distinct EPBD assessment, compliance and renovation processes while reducing repeated data collection.

A useful role for open tools

Open, standards-based tools can help make EPBD implementation more transparent. Their value lies not only in producing a result, but also in making the calculation logic, data structure and evidence links easier to understand and test. That is particularly important as building performance assessment becomes more digital and several policy instruments depend on overlapping building information.

For openBEP4EU, the challenge is to demonstrate how EPC calculation, SRI assessment and BACS-related evidence can be connected in practice. This can support more consistent implementation by Member States, help assessors follow clearer workflows and give building owners results that are easier to understand and act on. It can also give industry a more predictable basis for documenting technical building systems.

The next phase of EPBD implementation will need tools that work with real buildings, real documentation and real market capacity. A shared evidence base will not solve every implementation issue. It can, however, reduce duplication and improve confidence in the results.

One building should not have to tell its technical story five different ways.

Funding acknowledgement

openBEP4EU is funded by the European Union's LIFE Programme under Grant Agreement No. 101167613. The views expressed are those of the authors and do not necessarily reflect those of the European Union or CINEA.

References and further reading

[1]     Directive (EU) 2024/1275 on the energy performance of buildings (recast), especially Article 13 (technical building systems and BACS), Article 15 and Annex IV (SRI), Article 16 (data exchange), Articles 19-22 (EPCs and databases), and Article 23 (inspections). https://eur-lex.europa.eu/eli/dir/2024/1275/oj

[2]     European Commission, Energy Performance of Buildings Directive - implementation information and EPB standards overview. https://energy.ec.europa.eu/topics/energy-efficiency/energy-performance-buildings/energy-performance-buildings-directive_en

[3]     European Commission, Smart Readiness Indicator framework and implementation tools. https://energy.ec.europa.eu/topics/energy-efficiency/energy-performance-buildings/smart-readiness-indicator_en

[4]     ISO 52000-1, Energy performance of buildings - Overarching EPB assessment - Part 1: General framework and procedures. https://www.iso.org/standard/65696.html

[5]     EN ISO 52120-1, Energy performance of buildings - Contribution of building automation, controls and building management. https://www.iso.org/standard/69746.html

[6]     openBEP4EU, project outcomes and deliverables. https://www.openbep4.eu/outcomes/

[7]     eu.bac, updated EPBD BACS Compliance Verification Checklist and related guidance. https://eubac.org/news/eu-bac-updates-its-bacs-compliance-verification-checklist-to-match-the-reviewed-2024-epbd/