What an LCA measures

A Life Cycle Assessment quantifies the environmental impacts associated with a product across some or all of its life — raw material extraction, manufacturing, transport, use, and end-of-life. It's a general methodology, standardized by ISO 14040 and ISO 14044, used well beyond EPDs — for internal product design decisions, corporate reporting, and academic research. An EPD is one specific, standardized output format for LCA results, governed by additional rules an internal LCA study doesn't have to follow.

Functional unit and system boundary

Two decisions early in an LCA shape everything that follows. The functional unit is the precise, performance-based quantity being assessed — PCRs define this per product type so results are comparable across manufacturers. The system boundary defines which life-cycle stages and processes are actually included in the calculation — a "cradle-to-gate" LCA stops at the factory door; "cradle-to-grave" continues through use and disposal. A PCR specifies which boundary is required for that product category, so every EPD built against the same PCR uses the same one.

Life-cycle modules explained

EN 15804 and ISO 21930 break the product life cycle into standardized modules, and EPD results are reported against them individually rather than as one combined number:

  • A1–A3 (product stage): raw material supply, transport to the factory, and manufacturing.
  • A4–A5 (construction stage): transport to the building site and installation.
  • B1–B7 (use stage): use, maintenance, repair, replacement, refurbishment, and operational energy/water use.
  • C1–C4 (end-of-life stage): deconstruction, transport, waste processing, and disposal.
  • Module D: benefits and loads beyond the product's life — recycling or energy recovery potential — reported separately since it falls outside the product's own life cycle.

Many EPDs, particularly industry-average ones, report only A1–A3 ("cradle-to-gate") because use-stage and end-of-life data depend on assumptions the manufacturer can't fully control. Whether that's sufficient for a given purpose depends on what the EPD is being used for.

From LCA report to EPD document

An LCA practitioner's underlying study is typically a detailed technical report with far more granularity than what appears in the final EPD. Turning it into an EPD means mapping those results onto the exact structure the PCR requires — the right impact categories, the right module breakdown, the right supporting disclosures — and having an independent verifier confirm the mapping is accurate before a program operator publishes it. See How EPDs Work for the full process from data collection through publication.

Data quality and background databases

LCA results depend on two kinds of data: primary data the manufacturer measures directly (energy use, material inputs, production volumes at their own facility) and secondary data pulled from background databases for upstream processes they don't control, like the emissions associated with producing a raw material they purchase. ecoinvent is the most widely used commercial background database; PCRs sometimes require or recommend specific ones, and specify how old background data is allowed to be before it needs updating.

Frequently asked questions

Is an LCA the same thing as an EPD?

No. An LCA is the underlying study and calculation methodology. An EPD is the standardized, verified document that reports specific LCA results in a format defined by a PCR. Every EPD is based on an LCA, but an LCA on its own — without a PCR and third-party verification — is not an EPD.

What is a functional unit?

The functional unit is the precisely defined quantity of product performance the LCA measures impacts against — for example, '1 m² of flooring with a expected service life of 25 years,' not just '1 m² of flooring.' It's what makes results comparable between products that might otherwise have different service lives or performance characteristics.

What background databases are commonly used?

ecoinvent is the most widely used commercial background database internationally. Regional alternatives and datasets exist too — ÖKOBAUDAT in Germany, INIES in France — and PCRs sometimes specify which are acceptable for a given product category.

Why do impact categories matter beyond global warming potential?

Global warming potential gets the most public attention, but a product can shift impact rather than reduce it — for example, lowering carbon emissions while increasing water use or eutrophication elsewhere in the supply chain. Reporting multiple impact categories is what lets an EPD reveal that kind of tradeoff instead of hiding it.

Sources

  • ISO 14040:2006, Environmental management — Life cycle assessment — Principles and framework
  • ISO 14044:2006, Environmental management — Life cycle assessment — Requirements and guidelines
  • EN 15804:2012+A2:2019, Sustainability of construction works — Environmental product declarations — Core rules for the product category of construction products