ISO 14040 and ISO 14044: how the two work together
ISO 14040 sets the LCA framework; ISO 14044 defines the detailed requirements. They should be read as one body — practical difference, application order, and relation to EN 15804.
By clca Editorial TeamLast updated
ISO 14040 and ISO 14044 are two distinct but interdependent standards published in 2006. ISO 14040 defines "principles and framework" — what an LCA study is, what phases it consists of, what principles apply. ISO 14044 provides "requirements and guidelines" — the operational detail of what you must do. Treating them as separate is misleading; an LCA must satisfy both together.
The four LCA phases
- 1. Goal and scope definition — what you are assessing, for whom, and why
- 2. Life cycle inventory (LCI) — input/output data collection
- 3. Life cycle impact assessment (LCIA) — characterisation that converts inventory into impact categories
- 4. Interpretation — evaluation of results, sensitivity analysis, conclusion
ISO 14040 names these four phases; ISO 14044 specifies the methodological requirements per phase. The principle "define the functional unit explicitly" lives in 14040; the requirement "the functional unit must include performance, duration and quantitative values" lives in 14044.
When is a critical review mandatory?
ISO 14044 mandates a critical-review panel of independent experts for any LCA containing a "comparative assertion" — e.g. "my product has less environmental impact than competitor X". For non-comparative studies the review is optional, though recommended for major investment decisions and academic publications. The EN 15804+A2 EPD process is different — it mandates a verifier, which is a lighter audit than a classical critical review.
Relation to EN 15804
EN 15804+A2 is built on top of ISO 14040/14044. It takes the ISO framework and category-specialises it for construction products: mandatory module set (A1-D), 19 indicators, modulary table, verification process. ISO LCA produces "numerical results"; EN 15804 packages those into a standardised EPD document. An LCA scientist typically cites ISO directly; a manufacturer cites EN 15804.
Practical workflow
- Write the goal-scope document (ISO 14040 Clause 5 + ISO 14044 Clause 4.2 together)
- Set up the inventory template (ISO 14044 Clause 4.3)
- Choose the characterisation method (ISO 14044 Clause 4.4 — EF v3.1 recommended for EN 15804+A2)
- Interpret results (ISO 14044 Clause 4.5 — dominance, sensitivity, uncertainty)
- If there is a comparative assertion: appoint a critical-review panel
- If publishing an EPD: transfer the results into the EN 15804+A2 modulary table
Tags
- ISO 14040
- LCA standard
- LCA phases
- critical review LCA
Related reading
All articles in ISO Series- ISO Series
Functional unit vs declared unit: why getting it right matters
The functional unit must reflect performance; the declared unit reflects physical quantity. Confusing the two destroys EPD comparability.
10 min read - ISO Series
Comparative LCA and critical review: when is it mandatory?
Compare with a competing product and disclose it publicly, and ISO 14044 requires a review panel. The reasoning behind the rule and its practical consequences.
11 min read - ISO Series
Cut-off rules: what you are allowed to leave out
No LCA models every flow. How cut-off criteria are defined, the mass-energy-environmental relevance triad, and the most common mistake.
10 min read - ISO Series
The LCA allocation problem: mass, economic, and system expansion compared
When a process yields multiple products, how do you split the environmental burden? The ISO 14044 hierarchy, three main methods, and real industry examples.
11 min read