In accordance with EN 15941:2024 and EN 15804+A2, the selection of environmental data is a foundational methodological decision that governs the representativeness and therefore the credibility of EPDs.
This article summarises the four-tier hierarchy used to select data in One Click LCA software and the checks a LCA practitioner applies before locking in a dataset. All databases integrated in One Click LCA are methodologically aligned to the same reference level, so users can concentrate on identifying the dataset most representative of the project rather than reconciling different system models or impact-assessment methods.
The four-tier hierarchy
The tiers are ordered by specificity to the actual product, manufacturer and technology used. Move down a tier only when the higher one is unavailable or fails a representativeness check.
Tier 1 — Verified data covers the most defensible sources: a manufacturer-specific Type III EPD (1a), the same manufacturer's average or product-family EPD (1b), a collective sector EPD from an industry association (1c), and a critically reviewed independent LCA study (1d).
Tier 2 — Generic LCI dataset applies when no verified source covers the product. At this tier, database choice matters — see the following chapter ‘Selecting between Tier 2 databases’.
Tier 3 — One Click LCA generic profile is the fallback for materials outside the coverage of any public database. Certain profiles are curated by One Click LCA.
Tier 4 — Documented proxy is a last resort: use the closest technologically or geographically similar dataset, adapt per EN ISO 14044 Cl. 4.2.3.6.3, and document the substitution in the project report. The report must show the choice was conservative — the objective is representativeness, not favourability of the impact result (EN 15941 Cl. 8.4.4.2).
Four checks before locking in a dataset
Regardless of the tier, verify the dataset against four representativeness criteria drawn from EN 15941 Cl. 6.3–6.5 and Cl. 6.9:
Geographical — the dataset covers the country or region of manufacture at the highest available resolution (national → regional → continental → global).
Technological — the production route, feedstock and fuel mix match the actual product. Where the route is unknown, use a market-average rather than a best-case dataset.
Temporal — manufacturer EPDs remain valid five years from publication; generic LCI data must have a reference year within ten years (EN 15804+A2 Cl. 6.3.8.2). Always use the most recent database release.
Selecting between Tier 2 databases
When you reach Tier 2, the One Click LCA library is organised in three families. Choose the database whose sector, geography and vintage fit the project — the entries below are conditional guidance, not a ranking.
Some general-purpose databases (BAFU, ecoinvent, IDEMAT, ProBas) provide broad material and geographic coverage in a single backbone. Others are narrower but deeper in a specific domain: Carbon Minds for chemicals with country-level supply chains; WorldSteel for steel where a manufacturer EPD is unavailable; Plastics Europe for European bulk polymers.
When two generic databases both fit
EN 15941 Cl. 6.9 favours a consistent single-database backbone over an aggregation of sources. When two Tier 2 databases both pass the representativeness checks, three tie-breakers apply in order:
Dominant-database preference — remain on the primary LCI database already used elsewhere in the project.
Version recency — use the most recent release; if an earlier version is used, document the reason (EN 15941 Cl. 7.2.3.4).
Programme operator / national PCR — where a scheme prescribes a database (e.g., KBOB → BAFU, Dutch project → NMD), the local rule overrides general preference.
Every material — three-step checklist
For each item in the Bill of Materials:
Initiate at Tier 1a and cascade downward: manufacturer EPD → average → sector → reviewed LCA study.
Apply the four representativeness checks.
Record the source, version and reference year of the chosen dataset in the project file. Documentation is what makes the selection auditable under EN 15941 and EN 15804+A2.
Standards referenced
EN 15941:2024 · EN 15804:2012+A2:2019 · EN ISO 14025:2010 · EN ISO 14044:2006 · ISO 21930:2017 · ILCD Handbook (EC-JRC, 2010).
Where a national or programme-operator framework adds requirements (e.g., NMD, INIES, KBOB), the local rule takes precedence.
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