How to read an EPD: a guide for procurement and design teams

Read in a fixed order, an EPD can be understood in ten minutes: first the cover data (who published it, under which rules, valid until when), then the declared unit, then which life cycle modules are covered, then the GWP rows of the results table, and finally whether two declarations are comparable at all. The order is not arbitrary; each step is the precondition for the next one to mean anything. Without the declared unit a GWP value is meaningless; without the module scope two values cannot be placed side by side. Procurement and design teams read an EPD as users rather than verifiers — they ask not whether the document is correct, but whether it fits the decision in front of them.

Step 1 — Cover data: operator, PCR, validity, verifier

The first page gives five pieces of information. The programme operator (a body such as EPD International, IBU or ITB) is the party that publishes the document and sets its rules. The PCR — product category rules — and its version number say under which rules the calculation was made; two EPDs are comparable only if prepared under the same PCR. The standard applied (EN 15804+A2, ISO 14025, ISO 21930 where relevant) and in particular the +A2 designation matter: the +A1 version uses different characterisation factors and has not been accepted for new declarations since 2022. The publication and validity dates show the five-year window; an expired EPD is generally not accepted in green building certification. Finally the verifier: a document with a named independent third-party verification does not carry the same weight as one marked 'internal verification'. This section also states whether the EPD is product-specific, a manufacturer average or an industry average.

Step 2 — Declared unit and conversion

Every number in the results table is for one declared unit: 1 kg, 1 t, 1 m², 1 m³ or one piece of product. Even within one product group the unit changes — one insulation EPD may declare for '1 m² providing R = 1 m²K/W', another for '1 m³'. Values are not used until the quantity needed for the decision has been converted into that unit; the EPD's conversion table (density, thickness, mass per m²) exists for this purpose. Where a functional unit is declared — that is, the product's performance is also defined — the comparison is made on that performance: 'GWP per kg' says nothing about two insulation materials, 'GWP for the same thermal resistance' does. The reference service life (RSL) is also found here; if modules B and C are declared, they cannot be interpreted without it.

Step 3 — Module scope: which columns are filled?

Every EN 15804+A2 EPD contains a scope table showing which modules from A1 to D are declared; modules not declared are marked MND (module not declared). Under +A2 the rule, with exceptions, is that at least A1–A3, C1–C4 and D are declared; A4, A5 and the B modules depend on scenarios and, where present, come with scenario tables. For the reader the rule is one sentence: only columns of the same scope are compared. Placing one document's A1–A3 total beside another's A1–A5 total is the most common and most expensive mistake. Module D is always read separately and never added to the total — it is a potential benefit beyond the system, not a realised reduction.

Step 4 — Which row of the results table to look at

For most decisions the starting point is the GWP-total row and the A1–A3 column. GWP-total is the sum of three components: GWP-fossil (fossil fuel and process emissions), GWP-biogenic (the uptake and release of biogenic carbon) and GWP-luluc (land use and land use change). For timber or bio-based products GWP-biogenic is negative in A1–A3 and pulls the total down; if such products are to be compared with mineral ones, either the GWP-fossil row or the full life cycle including the C modules is used. Green building credits usually ask for the additional indicators too — acidification, eutrophication, ozone depletion, resource depletion — and these are further rows of the same table. For circularity assessment the SM row (secondary material input) in Table 11 and the MFR row (material for recycling) in Table 13 are consulted. Units deserve attention: kg CO₂ eq, kg SO₂ eq, MJ — even within one column the unit changes from row to row.

Step 5 — Comparability conditions

EN 15804 states explicitly that two EPDs can only be compared when specific conditions are met, and requires every document to carry a warning to that effect. The conditions: the same PCR, the same functional unit (or the same declared unit plus the same performance and RSL), the same module scope, the same version of the standard and the building context — that is, the product's function and service life in the building. In practice four checks suffice for procurement: are both +A2, are both product-specific, do both use the same unit and scope, do the products perform the same function. If a pair passes all four, the GWP difference is meaningful; if not, the difference is a difference between documents, not between products. Where product lives differ (a 25-year finish against a 50-year finish) an A1–A3 comparison misleads; a comparison over the building's life including the B4 replacement module is needed.

Red flags

• Validity date passed or standard version +A1: values cannot be compared with +A2 documents
• No verifier named or 'internal verification': third-party assurance is missing
• C and D modules MND without justification: mandatory under +A2 except in defined exceptions
• An industry-average document presented as product-specific: check the type on the cover
• Negative GWP-total with no biogenic carbon explanation: temporary storage may be shown as a permanent saving
• Declared unit 'piece' or 'pack' without mass and density: no conversion is possible
• Values far below the product group's typical range: data coverage or allocation should be questioned
• A 'carbon neutral' or 'climate friendly' claim inside the document: ISO 14025 does not allow comparative claims in an EPD

Moving EPD data into a building LCA

For the design team the final use of an EPD is the building model. The transfer is made with four records: the EPD number and version, the declared unit, the module values taken (A1–A3, and C1–C4 and D separately where present) and the scenarios replaced to suit the project — the A4 distance and the module C end-of-life route are entered from the project's reality, not from the EPD's scenario. The quantity is the product quantity in the element plus site wastage. Retyping from a PDF is a source of error; machine-readable EPD formats (such as ILCD+EPD) and the programme operators' digital libraries transfer values directly. The building LCA report lists which EPD was used for which product and what happens when one expires; the certification audit asks for that list.