Reading an EPD,
without the chemistry.
A practical guide to the four sections of an Environmental Product Declaration that actually decide a comparison.
A practical guide to the four sections of an Environmental Product Declaration that actually decide a comparison.
An Environmental Product Declaration is long, standardised, and written for LCA practitioners rather than architects. Most of it you can skip. Four things on it decide whether one product is genuinely lower-impact than another.
Every EPD states its scope using the EN 15804 stage codes: A1-A3 covers raw material supply, transport, and manufacturing — "cradle to gate." A1-C4 extends that through the product's use phase and end of life — "cradle to grave." A product quoted only on A1-A3 numbers looks better than one quoted on A1-C4, even if the underlying materials are identical, simply because less of the lifecycle is counted. Always check which stages a number covers before comparing it to another product's number.
Global Warming Potential gets split into fossil and biogenic components. GWP-fossil is emissions from burning fossil fuels — the number you want to see low. GWP-biogenic is often negative on wood-based products, because growing wood captures atmospheric carbon that gets temporarily stored in the material. That's real and worth noting, but it's a different kind of number from an emissions reduction — it's stored carbon, not avoided carbon, and it's released again at end of life unless the product is genuinely recycled rather than incinerated or landfilled.
Every EPD declares a functional unit — usually "per m²" or "per kg" of product, at a specified thickness or density. Comparing a 20 mm tile's per-m² figure against a 40 mm tile's per-m² figure will make the thinner product look better, because it is, per square metre, using less material — which may or may not be the comparison you actually need for your specific application. Always check the declared unit matches what you're actually specifying.
An EPD is only as credible as its verification. A third-party-verified, program-operator-issued EPD (through a registered EPD programme) has been checked against the underlying LCA data by someone with no stake in the result. A self-declared environmental claim without that verification step is a marketing statement wearing an EPD's format — worth asking about, not worth treating as equivalent.