Lifecycle Carbon of FRP vs Steel: How to Read an EPD

In short: An EPD (Environmental Product Declaration) is a verified report of a product's life cycle impacts, made under ISO 14025 and, for construction products in Europe, EN 15804+A2. To compare FRP and steel fairly, check that both EPDs use the same product category rules, cover the same modules (A1–A3 production, C1–C4 end of life, D beyond the system boundary), and convert to the same functional unit, such as one square meter of walkway carrying the same load for the same service life. A lower number per kilogram means little on its own. FIBROVX builds each item to order.

How this guide fits with our others

This guide covers how to read and compare EPDs. For what happens to FRP at end of life (module C and D in EPD terms), see can FRP be recycled. For a cost comparison over time, see FRP vs steel grating: total cost of ownership over 20 years. Sectors we serve are on our industries page.

What an EPD is

• ISO 14025 defines EPDs as Type III environmental declarations: quantified environmental data based on a life cycle assessment (LCA), independently verified and managed by a program operator, as summarized by the German flat glass association's EPD bulletin.
• For construction products, EN 15804 sets the core rules. The current version is EN 15804:2012+A2:2019+AC:2021.
• Product Category Rules (PCR) add rules for a specific product group. Two EPDs built on the same PCR are much easier to compare.
• The program operator publishes the EPD, maintains the rules and oversees verification.

The life cycle modules

EN 15804 splits a product's life into modules. The main ones:

Under EN 15804+A2, construction product EPDs must declare A1–A3, C1–C4 and D, with a few exceptions set in the standard. A4 to B7 are optional. BRE's PCR describes the types: cradle to gate with C and D, cradle to gate with options, and cradle to grave with D.

Read these fields first

1. Declared unit or functional unit

Many EPDs report per declared unit, such as 1 kg, 1 m² or 1 m³. ISO 14025 asks for an identical functional unit when comparing; the UK Construction Products Association notes that EN 15804 EPDs can use a declared unit instead. You then need to convert to the same function. For grating, that means the mass per square meter of each product that meets the same load and deflection over the same span.

If an EPD does not report per kilogram, the Construction Products Association says it should include a factor to convert the declared unit to mass. Use that factor to rebuild the number for your own quantity.

2. GWP indicators

EN 15804+A2 reports climate change in several indicators, listed in BRE's PCR:

• GWP-total, the headline figure;
• GWP-fossil, from fossil sources;
• GWP-biogenic, from biogenic carbon;
• GWP-luluc, from land use and land use change.

Compare like with like: GWP-total against GWP-total, for the same modules.

3. Modules declared

Check which modules have numbers and which say "ND" (not declared). A cradle-to-gate figure (A1–A3) leaves out installation, maintenance, replacement and end of life.

4. Module D

Module D reports benefits and loads beyond the system boundary, such as credits for recycling or energy recovery. Read it separately from A–C.

5. Data and validity

Check whether the data is product specific (one plant) or an average (several plants or an industry). Under EN 15804+A2 an EPD is valid for up to 5 years from issue, after which it must be reviewed and verified, according to BRE's PCR.

6. Scenarios

Modules A4 to C4 depend on assumptions: transport distance, installation method, service life, and what happens at end of life. EN 15804 allows that where scenarios in one or both EPDs are missing or do not fit, they should be generated from the specific building conditions for the comparison, as the CPA review notes. Write down the scenarios you use for both materials.

The EPD types you will see

The Bau EPD template, written to EN 15804+A2, lists the types an EPD can take:

• Cradle to gate with modules C1–C4 and D (A1–A3 + C + D);
• Cradle to gate with options (A1–A3 + C + D, plus one or more of A4 to B7);
• Cradle to grave with module D (A + B + C + D).

The German flat glass association's bulletin uses these names for the module groups: A1–A3 is cradle to gate, A1–A5 is cradle to practical completion, A1–C4 is cradle to grave, and adding module D is called cradle to cradle. It warns that this use of "cradle to cradle" must not be confused with the certification system of that name, and that even a full EPD describes a linear life, not a closed loop.

When can two EPDs be compared?

ISO 14025 clause 6.7.2 sets the conditions. The UK Construction Products Association summarizes them: the same product category definition, functional unit and cut-off rules; equivalent system boundaries, data quality, allocation and impact methods; the same validity period; and, for modular EPDs, omitted stages must be insignificant or identical.

The CPA calls this list a stringent set of criteria.

EN 15804 adds that comparisons should be based on the product's use in and impact on the building and the complete life cycle. A sub-building comparison is allowed only when:

• the same functional requirements are met;
• anything left out performs the same and is the same amount;
• the same modules are left out;
• the product's effect on the building's operation is taken into account;
• biogenic carbon and other inherent properties are handled the same way.

EPD International adds that two EPDs registered under the same PCR in the same program are the easiest to compare. Otherwise the reader has to check the conditions.

FRP vs steel: where the numbers come from

Do not compare per kilogram. A square meter of FRP grating and a square meter of steel grating weigh different amounts and last different times in a given environment. Build the comparison on the function:

1. Same duty: span, load, deflection limit and surface.
2. Same life: the service period of the project, with replacements counted in module B4 where one material will be replaced.
3. Same maintenance: coatings or repairs in module B2/B3, if one material needs them in your environment.
4. Same end of life: say what happens in C1–C4 and D for both (for FRP, see the routes in can FRP be recycled).

A worked layout (illustrative, no real data)

Suppose a walkway needs 100 m² of grating over a given span and load, for a 25-year project. A fair comparison table has one row per material and these columns:

• mass per m² that meets the duty (from each supplier's load table);
• A1–A3 GWP-total per kg (from each EPD), multiplied by the mass;
• A4 transport to your site, using your own distance;
• B2–B4 maintenance and replacements over 25 years in your environment;
• C1–C4 end of life, and module D shown in a separate column.

Fill it with your project's numbers. The layout matters more than any single figure, because the per-kilogram value alone ignores mass, life and maintenance.

Corrosion matters here. Where steel needs recoating or replacement in a chemical or marine site, those modules can change the result. Where it does not, they will not. Use your own site data, not a general claim.

EPD comparison checklist

1. Confirm both EPDs follow EN 15804+A2 (or the same PCR).
2. List the modules each declares; mark gaps.
3. Convert each to the same functional unit for your project.
4. Add use-stage maintenance and replacement for your site.
5. Compare GWP-total for A–C; read module D separately.
6. Check data type and validity date.

What to ask a supplier for

If you are comparing quotes for an FRP and a steel option, the request itself decides how useful the answer will be. A vague "send us your carbon data" usually returns a brochure number with no boundary. A precise request gets you something you can check. These are the points we suggest putting in writing.

1. The EPD document itself, not a summary sheet. Ask for the full PDF with its registration number, so you can look it up with the program operator.
2. The declared or functional unit, and the mass conversion factor if the unit is per kilogram. Without it you cannot turn the result into a per-panel or per-meter figure.
3. The modules included. Ask the supplier to list every module that is declared and every module that is marked as not declared.
4. Whether the EPD is product-specific or an industry average, and which plants it covers.
5. The validity dates. An EPD has a set validity period; check that it has not expired.
6. The end-of-life scenario used in modules C and D, in plain words.

For your own project, ask for the same unit on both sides. If one supplier gives a per-kilogram figure and the other a per-square-meter figure, convert both to the same installed item before you look at the totals. For grating, that is often one square meter of panel at the span and load you specified. For a tank or a pipe run, it is the whole item. Keep the converted numbers with the source EPD numbers in one table, so anyone reviewing the comparison can follow each step.

How we customize

FIBROVX makes molded grating, pultruded profiles, water tanks and other FRP items to your drawings. For a carbon comparison, we can give you the item data an LCA practitioner needs, such as mass per item, resin type and glass content, for the items you order. A product-specific EPD is custom / available on request; ask us what can be provided for your project. See custom FRP manufacturing.

FAQ

Does FRP have a lower carbon footprint than steel?

It depends on the functional unit, the modules counted and the site. Compare EPDs on the same function and life, not per kilogram.

What is module D in an EPD?

Benefits and loads beyond the system boundary, such as credits from recycling or energy recovery. Read it separately.

How long is an EPD valid?

Under EN 15804+A2, up to 5 years from issue, then it is reviewed and verified.

What is a declared unit?

The reference quantity an EPD reports per, such as 1 kg, 1 m² or 1 m³. Convert it to your project's function before comparing.

Can I compare two EPDs from different programs?

Only if the ISO 14025 clause 6.7.2 conditions are met. EPDs under the same PCR are easiest to compare.

Related: FRP Grating vs Steel Grating: Weight, Corrosion and Where Each Wins.

Sources

• BRE Global, PCR for Type III EPD of construction products to EN 15804+A2, PN 514 Rev 3.1 (comparability 5.3, GWP indicators, 5-year validity): https://www.greenbooklive.com/filelibrary/EN_15804/BRE-PN514-EN15804-A2-PCR-V3.1.pdf
• Construction Products Association, EPD Comparability: a technical review (2024): https://constructionproducts.org.uk/media/xqnn3jfl/cpa-bp-epd-comparability-a-technical-review-v1-august-2024-final.pdf
• EPD International, What is the requirement for comparability of EPDs?: https://environdec.freshdesk.com/support/solutions/articles/206000057940-what-is-the-requirement-for-comparability-of-epds-
• Bundesverband Flachglas, Bulletin 024/2024 Environmental Product Declaration (Type III, program operator, EN 15804 current version, module groups): https://www.bundesverband-flachglas.de/wp-content/uploads/simple-file-list/bf-bulletins/BF_Bulletin_024-2024_Environmental-Product-Declaration_EPD_EN.pdf
• Bau EPD, project report template to EN 15804+A2 (A1–A3, C1–C4 and D required; EPD types): https://www.bau-epd.at/fileadmin/user_upload/PCR_general_docs_English/BAU-EPD-M-DOCUMENT-13A2-project-report-content-and-format-template-EN15804_A2-version10.0-date-2026-02-19-English-Website.pdf