KRAISBAU data cascade – methodological approaches for circular construction

Background

Four questions determine the circularity of a building: What is installed? What condition is it in? How are elements, products and materials connected to each other? And what does this mean for the life cycle? The European life cycle assessment standards EN 15804 and EN 15978 do not adequately answer any of these questions – their focus is on environmental impact categories such as GWP, AP or EP, not on circularity parameters (Van Gulck, Wastiels and Steeman 2022; CEN 2019; CEN 2011). Without this data basis, decisions on conversion versus demolition remain speculative.

Clarity is urgently needed: According to current UNEP data, the building sector accounts for 32% of global energy consumption and 34% of energy and process-related COâ‚‚ emissions (UNEP and GlobalABC 2024). The European Commission estimates that around half of all materials extracted worldwide flow into the construction sector (European Commission n.d.). So the resources are being used – we just don’t know where exactly, in what quantity and in what condition.

The BMIMI/ffg lead project KRAISBAU (2024-2028) with 32 partners along the construction value chain is addressing this methodological gap.

The KRAISBAU data cascade

After one and a half years of project work, a conceptual framework has crystallized that brings the project’s methodological approaches into a logical sequence: a three-stage data cascade that leads from quantification to condition assessment to life cycle assessment – and is thus intended to unlock data-based planning decisions.

Stage 1: Quantification – “What is there?”

The first stage answers the question of the material stock. Material flow modeling at regional and district level is used to quantify secondary material potential in the Austrian building stock. The methodology combines bottom-up and top-down approaches: Building archetypes are validated with actual residual building mass data to enable area-wide statements about available resources. The project is led by Fraunhofer Austria Research in collaboration with the Vienna University of Technology.

Stage 2: Condition assessment – “How good is it still?”

While stage 1 clarifies availability, stage 2 deals with qualitative performance as a prerequisite for high-quality reuse scenarios. A key aspect is the development of a degradation database in accordance with ISO 15686, which correlates physical damage patterns with specific remaining useful lives. Influencing factors are systematically recorded for the key materials concrete, steel, wood and masonry in order to train a deep learning-based model for predictive condition assessment. To this end, BOKU Vienna is validating innovative NDT methods (near-infrared spectroscopy and ultrasound) to collect material parameters directly on the object in a non-destructive manner. This forms the technical data basis for design-for-reuse concepts (Task 4.4) by making it possible to objectively assess the technical recoverability and dismantling costs.

Stage 3: Life cycle assessment – “What does this mean in the life cycle?”

The third stage integrates the data obtained into established evaluation frameworks. Together with Graz University of Technology, the Institute of Industrial Ecology (IIÖ) is developing a “Circular Economy Calculator” that calculates circular economy indicators: the Material Circularity Indicator (MCI) according to the methodology of the Ellen MacArthur Foundation (Ellen MacArthur Foundation and Granta Design 2019), indicators for deconstructability and the circularity factor ZiFa developed at BOKU (Kromoser et al. 2024). The connection to the EU taxonomy enables the link to regulatory requirements.

Decision support for the building turnaround

The core challenge of modern building development lies in balancing the preservation of gray energy and the economic efficiency of selective dismantling. Where is the “break-even” point at which the ecological advantage of reuse justifies the higher dismantling costs?

This decision-making gap is currently being closed by methodically linking condition data and life cycle analyses. The Pioniergarage Salzburg real-world laboratory is testing how high-resolution digital inventories can secure this calculation. In order to transfer this systemic change from niche to standard, the consortium is relying on a radical open knowledge approach: the results flow directly into the design and rapid prototyping of scalable training programs, construction coaching and factsheets for the entire value chain.

Outlook

The methodological insight is clear: EN 15804 is necessary but not sufficient for an operationalized circular economy (Van Gulck et al. 2022). The data cascade provides the complementary assessment framework that is essential for making informed decisions about existing buildings. AI-supported and digitally scaled, we are thus transforming the current data gap into a resilient industry standard for circular construction.

Further information

• KRAISBAU project: www.kraisbau.at
• Circular Economy Forum Austria: www.circulareconomyforum.at
• FHWien der WKW, Endowed Chair of Sustainable Real Estate Development

Sources

CEN – European Committee for Standardization (2011) EN 15978:2011 – Sustainability of construction works – Assessment of environmental performance of buildings – Calculation method. Brussels: CEN.

CEN – European Committee for Standardization (2019) EN 15804:2012+A2:2019 – Sustainability of construction works – Environmental product declarations – Core rules for the product category of construction products. Brussels: CEN.

Ellen MacArthur Foundation and Granta Design (2019) Circularity Indicators: An Approach to Measuring Circularity – Methodology. Cowes: Ellen MacArthur Foundation. Available at: https://www.ellenmacarthurfoundation.org/material-circularity-indicator (Retrieved: 27.01.2026).

European Commission (n.d.) Buildings and construction. [Online]. Available at: https://single-market-economy.ec.europa.eu/industry/sustainability/buildings-and-construction_en (Retrieved: 27.01.2026).

ISO – International Organization for Standardization (2011) ISO 15686-1:2011 – Buildings and constructed assets – Service life planning – Part 1: General principles and framework. Geneva: ISO.

Kromoser, B., Hammerl, M., Camargo, I., Bankl, V., Klammer, M., Amler, F. et al. (2024) Orientation Guide Circularity Factor ZiFa 1.0: Development of Assessment Parameters for Circular Building and Refurbishment. Vienna: Municipal Directorate, Buildings and Technology Division. Available at: https://www.wien.gv.at/spezial/studien/mdbd/orientierungsleitfadenzirkularitaetsfaktor2024.pdf (Retrieved: 27.01.2026).

UNEP – United Nations Environment Programme and GlobalABC – Global Alliance for Buildings and Construction (2024) Global Status Report for Buildings and Construction 2024/2025: Not just another brick in the wall. Nairobi: UNEP. Available at: https://www.unep.org/resources/report/global-status-report-buildings-and-construction-20242025 (Retrieved: 27.01.2026).

Van Gulck, L., Wastiels, L. and Steeman, M. (2022) ‘How to evaluate circularity through an LCA study based on the standards EN 15804 and EN 15978’, The International Journal of Life Cycle Assessment, 27(12), pp. 1249-1266. doi: 10.1007/s11367-022-02099-w.