A practical guide for sustainability professionals: where to find EPDs, what data to extract, how to read a GWP table, and when to use generic factors vs manufacturer-specific values.
An Environmental Product Declaration (EPD) is a standardised document that quantifies the environmental impact of a product across its life cycle. For embodied carbon analysis, EPDs following EN 15804+A2:2019 are the gold standard — they report impacts across all life cycle modules using a consistent methodology.
For most early-stage BoM analysis, you need three things from an EPD:
| Data point | What it is | Where to find it in the EPD |
|---|---|---|
| GWP A1–A3 required | Global Warming Potential for the production stage — manufacturing, raw material extraction, and transport to factory gate. The most important number for BoM analysis. | Results table, row labelled "GWP-total" or "GWP", column "A1–A3" or "A1-A3 sum". Units: kg CO₂e per declared unit. |
| Declared unit required | The unit the EPD is expressed per. Usually kg, m², m³, or piece. Critical for unit conversion in your BoM. |
Product description section, often near the top of the EPD. Look for "Declared unit" or "Functional unit". |
| Density useful | Product density in kg/m³. Needed if the declared unit is m² or m³ and your BoM quantities are in kg, or vice versa. | Product description section. May be labelled "bulk density", "apparent density", or given as mass per declared unit (e.g. "16 kg per m²"). |
| C1–C4 & Module D optional | End-of-life stage impacts and net benefits beyond system boundary. Not needed for A1–A3 analysis but useful for whole-life carbon. | Same results table as A1–A3, columns C1, C2, C3, C4, and D. |
ef value. Older EPDs following EN 15804+A1 report a single "GWP" value — this is equivalent to GWP-total for most materials.
EPDs are published by EPD programme operators — independent organisations that verify EPDs against ISO 14025 and EN 15804. The main registries are:
Many major manufacturers now publish EPDs directly on their product pages. Rockwool, Paroc, Saint-Gobain, BASF, Kingspan, ArcelorMittal, Holcim, and others maintain dedicated EPD libraries. If you can't find an EPD via a programme registry, check the manufacturer's sustainability or technical documentation section. Search for "[product name] EPD PDF" and you will often find it.
EN 15804 EPDs follow a standardised results table structure. Here is what each column means:
ef.c1–c4.d but excludes from project totals.ND (Not Declared) means the manufacturer has not provided data for that module — not that the impact is zero. For early-stage analysis, you can treat ND as zero with a note in your assumptions. For formal reporting, ND modules must be handled according to the project's assessment rules.
Negative GWP values are valid and correct. They most often appear in Module D (recycling credit), and occasionally in biogenic carbon-storing materials like timber (where carbon sequestered during growth is released or stored). A negative value in A1–A3 for a timber product typically means the product stores more carbon than is emitted during manufacturing — this is real but contested in how it should be counted.
m² or m³ and your BoM quantities are in kg, you need the product density. Multiply: GWP (kg CO₂e/m²) ÷ (density kg/m² or kg/m³ × thickness) to get kg CO₂e/kg. Alternatively, keep quantities in m² or m³ to match the EPD's declared unit — this is often cleaner.
Two types of GWP data are available for embodied carbon analysis. Understanding the difference is essential for knowing when to use each.
| Generic factors (e.g. EPiC 2024) | Manufacturer EPDs | |
|---|---|---|
| Accuracy | Industry average — correct order of magnitude | Product-specific — most accurate available |
| Availability | Immediate — no searching required | Requires finding and reading each EPD |
| Geographic scope | Country/region average (EPiC = Australian supply chain) | Specific to manufacturer's plant and supply chain |
| Time to use | Seconds | 5–15 minutes per product |
| Accepted for formal reporting | Generally not — indicative only | Yes, when verified and current |
| Useful for | Early design, material comparison, budget estimates, design decisions | BREEAM credits, planning conditions, contractor BoMs, procurement specifications |
| Risk | Can over- or under-estimate by 30–200% for specific products | Low if EPD is current and scope matches your application |
Use generic factors when: you are comparing material options at concept stage, you don't yet have a confirmed specification, you need a quick order-of-magnitude check, or no relevant EPD exists for the product.
Use manufacturer EPDs when: the product specification is confirmed, you are preparing documentation for BREEAM, LEED, or a planning condition, you want to reward a supplier's low-carbon product with accurate numbers, or the project brief requires product-specific data.
A practical step-by-step workflow for assembling embodied carbon data for a bill of materials at early design stage.
From drawings, specifications, or engineer's schedule: list each material/product with its quantity. Use the units that match the EPD declared unit where possible (m² for boards and insulation, m³ for concrete, kg for steel, pcs for windows and doors). At concept stage, area and volume from the model is usually enough.
Concrete, steel, timber, and insulation typically account for 80–90% of embodied carbon in a building. Start with these. Finishes, services, and fit-out can follow. Use a 20/80 rule: find EPDs for the 20% of materials that represent 80% of mass or expected carbon.
For each priority material: check EPD programme registries first. If no relevant EPD exists or the specification isn't finalised, use the equivalent FastLCA generic factor and note it as "generic — EPiC 2024". Record the source and date for every value.
For each EPD: open the PDF, find the results table, read the GWP-total A1–A3 value, and note the declared unit. Use the FastLCA EPD Extractor to do this quickly and format it for your database. Check the units carefully — an error here flows through all calculations.
If your BoM quantity is in kg but the EPD is in m²: multiply GWP/m² by the number of m², or convert using density × thickness. FastLCA handles unit conversion automatically when density is provided. For manual calculations: total GWP = quantity × GWP per declared unit.
Note which values are generic vs product-specific, the date you retrieved the EPD, and any assumptions on density or unit conversion. This is essential for audit trails and allows others to verify or update the analysis. FastLCA stores source references for every line item.
The FastLCA EPD Extractor reads GWP values directly from EN 15804 EPD PDFs and formats them for your FastLCA Google Sheet database — no manual copying of numbers.
Drag and drop or click to upload. The extractor reads the PDF in your browser — the file is not sent to any server. Processing takes 2–5 seconds.
The extractor shows GWP-total A1–A3, C1–C4, and Module D. The EPD registration number and publication year are auto-filled where found in the PDF text. Click any cell to correct a value if needed.
Add product name, ID, category, manufacturer, declared unit, density, and the EPD URL. This becomes the full database row. The ID is a short unique key you choose (e.g. paroc_extra_100mm).
Click "Build Google Sheet row" to preview all 19 columns, then "Copy row to clipboard". Open your FastLCA Google Sheet → Section B → click first empty cell in column A of the next empty row → Ctrl+V. All 19 columns paste at once.
The EPD Extractor is a separate tool hosted at /FastLCA_EPD_Extractor_v2.html. Upload it to your GitHub repo alongside index.html to make it available.
EN 15804+A2 reports four GWP indicators: GWP-total, GWP-fossil, GWP-biogenic, and GWP-LULUC. Always use GWP-total unless the project brief specifically requires a different indicator. GWP-fossil alone understates total impact for biogenic materials; GWP-biogenic alone can be negative and misleading out of context.
This is the most common numerical error. An EPD may say "2.3 kg CO₂e" — but per what? Per kg? Per m²? Per piece? Always read the declared unit and convert your BoM quantities accordingly before multiplying. A 12mm plasterboard EPD declared per m² cannot be directly multiplied by a weight in kg without conversion.
EN 15804 EPDs are valid for 5 years. After expiry, the EPD is no longer verified as current. Check the "valid until" date in the EPD document. For formal reporting, expired EPDs should be flagged and the project team should seek an updated version.
A1–A3 covers production only. Whole-life carbon includes A4 (transport), A5 (construction), B-stages (use), C-stages (end of life), and Module D. For embodied carbon BoMs at design stage, A1–A3 is standard — but be explicit about this scope boundary in any reporting.
ND (Not Declared) means the manufacturer chose not to report that module — it does not mean the impact is zero. For sensitivity analysis, consider testing with estimated values for key ND modules. For formal reporting, follow the project's Assessment Methodology Rules.
EPiC values (hybrid LCI) and EN 15804 EPD values (process-based LCI) are not directly comparable. Hybrid values are systematically higher because they capture more of the supply chain. If your BoM mixes both, note which values come from which source and be consistent in how you present comparisons.
Use FastLCA to calculate GWP for construction assemblies — add your own EPDs or use the built-in EPiC 2024 generic factors.
Open FastLCA calculator Open EPD Extractor