Materials & Embodied Carbon · EN 15804+A2
Embodied Carbon — Timber & Bio-Materials Calculator (CLT / Glulam / Softwood / Hardwood)
Audit-grade cradle-to-grave embodied carbon for engineered and sawn timber, plus bio-based insulation, to EN 15804+A2 and EN 15978. Module A1–A3, C3, C4 and D reported as separate life-cycle lines, with the biogenic carbon term split from the fossil term per the EN 15804 GWP identity. AR5 GWP-100 throughout. Factors from ÖKOBAUDAT 2024. Module D never nets into the A–C total.
Modular life-cycle architecture (EN 15804+A2 / EN 15978):
Embodied carbon is reported by life-cycle module, not as a single aggregate.
This calculator computes (A1–A3) product stage (cradle-to-gate);
(C3) waste processing and (C4) disposal at end-of-life; and
(D) benefits and loads beyond the system boundary (reuse, recovery,
recycling). The headline reportable figure is the cradle-to-grave
A–C total. Module D is reported on its own line and is never
added into A–C.
Product stage (A1–A3): Cradle-to-gate emissions from raw-material supply, transport, and manufacture. For timber these values are net-negative per cubic metre because the EN 15804 A1–A3 figure includes the biogenic carbon taken up by the growing tree. Factors are ÖKOBAUDAT 2024 EN 15804+A2 / EF 3.1 datasets, declared per m³.
Biogenic vs fossil split (the EN 15804 identity): GWPtotal = GWPfossil + GWPbiogenic + GWPluluc. The calculator surfaces the GWPbiogenic term separately from the fossil-plus-land-use remainder so you can see how much of the net-negative A1–A3 figure is sequestered carbon (released again at end-of-life) versus a genuine fossil reduction. Biogenic carbon is reported, not netted into a “carbon-negative” headline.
End-of-life (C3 / C4): C3 (waste processing) captures the release of the stored biogenic carbon when timber is incinerated or decays — which is why C3 is positive and broadly offsets the negative A1–A3 figure over the full life cycle. C4 (final disposal to landfill) exists only for the engineered-panel and wood-fibre rows in this dataset; sawn timber and the agri-fibre insulants carry no C4 row.
Module D (reuse / recovery credit): Net benefit from reuse, energy recovery, or recycling beyond the system boundary. Reported as a separate line per EN 15804+A2. Under both EN 15978 and RICS Whole Life Carbon Assessment, Module D is disclosed alongside — never inside — the A–C total.
Scope boundary: embodied carbon in purchased construction materials sits in Scope 3 Category 2 (capital goods) for the asset owner, or Category 1 for a contractor purchasing for resale. This calculator computes the material embodied carbon; mapping to a Scope 3 category is a boundary decision set in your inventory methodology. Excluded: the construction process stage (A4–A5), in-use stage (B1–B7), and operational energy — those belong to a whole-building assessment (EN 15978).
A–C (cradle-to-grave) is the recommended, complete view. A1–A3 alone omits the end-of-life release of stored biogenic carbon.
Add a material and enter a quantity above to calculate
Results appear instantly. Timber stores biogenic carbon (A1–A3 is often negative) but releases it at end-of-life — the whole-life boundary toggle, the biogenic-vs-fossil split, the module breakdown and the full audit trail appear after calculation.
Results are indicative whole-life (EN 15804+A2 / EN 15978) embodied-carbon estimates for timber, engineered-wood and bio-based insulation products, reported as GHG Protocol Scope 3 Category 2 (Capital Goods) on an AR5-100 GWP basis. Factors are ÖKOBAUDAT 2024 generic / average datasets. Module A1–A3 is net of the biogenic carbon the plant stored during growth (EN 15804+A2 GWPbiogenic), so it is typically negative for timber — but that carbon is a temporary store, released back to atmosphere at end-of-life (module C3) unless the product is reused or landfilled. Report A–C (cradle-to-grave), not A1–A3 alone, for a complete inventory. Module D (energy-recovery / reuse credit) is reported separately under EN 15804 and is never netted into A–C. The result excludes A4 transport to site, A5 installation, and B in-use. A biogenic-storage claim is only defensible for legally and sustainably sourced timber (FSC / PEFC chain-of-custody). Confirm quantities, densities and factors against product-specific EPDs and your own records, and where material proceed to third-party verification under EN 15978 / ISO 14064-3.
Timber is the one structural material whose cradle-to-gate carbon figure is negative — a cubic metre of cross-laminated timber carries roughly −660 kg CO₂e at module A1–A3, because the EN 15804 product-stage figure includes the carbon the tree absorbed while growing. That single fact drives most of the misreporting in timber Scope 3 inventories.
A negative A1–A3 number is not a carbon-negative building product. The stored biogenic carbon returns to the atmosphere at end-of-life (module C), the reportable figure is the cradle-to-grave A–C total — not A1–A3 alone — and Module D never nets into it. This calculator computes A1–A3, C3, C4 and D as separate EN 15804+A2 lines, splits the biogenic term from the fossil term, and shows why two of the bio-based insulants here are net-positive.
Cross-laminated timber has an A1–A3 embodied carbon of about −660 kg CO₂e/m³ — net-negative because EN 15804 counts the tree’s biogenic carbon uptake. Over the full life cycle (A–C) that stored carbon is released again, so the cradle-to-grave figure is near-neutral, not negative.
A timber element’s net-negative A1–A3 value reflects biogenic carbon that is released again when the material is incinerated or decays at end-of-life (module C). The figure you disclose to EN 15978, RICS WLCA, or a Scope 3 inventory is the cradle-to-grave A–C total. Module D — the reuse or energy-recovery credit — is reported on its own line and never added into A–C. This calculator enforces that separation automatically.
Roll up to a whole-building EN 15978 assessment →
What Is Embodied Carbon in Timber and Bio-Materials?
Embodied carbon is the greenhouse gas associated with producing, transporting, maintaining, and disposing of a material — as distinct from the operational carbon of running the building it sits in. For construction materials it is quantified using Environmental Product Declarations (EPDs) prepared to EN 15804+A2, which divides the life cycle into modules: A1–A3 product stage, A4–A5 construction, B1–B7 use, C1–C4 end-of-life, and D for benefits and loads beyond the system boundary.
This calculator covers the modules that are intrinsic to the material itself — A1–A3, C3, C4, and D — for engineered timber (CLT, glulam, LVL, OSB, plywood), sawn softwood and hardwood, and a set of bio-based insulants. It expresses every result in kg CO₂e using IPCC AR5 100-year global warming potentials, consistent with the ÖKOBAUDAT 2024 datasets it draws from.
Cradle-to-Gate (A1–A3) vs Cradle-to-Grave (A–C)
Cradle-to-gate (A1–A3) is the most frequently quoted embodied-carbon figure, and for timber it is the most frequently misread. A1–A3 is net-negative per cubic metre because EN 15804 includes the biogenic CO₂ the tree sequestered during growth. The cradle-to-grave figure (A–C) adds the end-of-life modules, where that stored carbon is released — so the honest, reportable number is the A–C total, which for most timber products lands close to neutral rather than negative.
Why Timber Is the One Material That Can Show a Negative Product Stage
Concrete, steel, and aluminium have no biogenic carbon term — their A1–A3 figures are unambiguously positive (a cubic metre of ready-mix C30/37 is about +196 kg CO₂e, structural steel about +0.56 kg CO₂e per kg). Timber is different: the wood holds carbon drawn from the atmosphere, and EN 15804 records that uptake as a negative contribution at A1–A3. This is an accounting convention, not a free emission reduction — the section below explains why.
Included vs Excluded
| Included in this calculator | Excluded — assess elsewhere |
|---|---|
| A1–A3 product-stage embodied carbon (per m³) | A4 transport to site and A5 construction/installation — project-specific |
| Biogenic carbon term, split from the fossil term | B1–B7 in-use stage (maintenance, replacement, operational energy) |
| C3 waste processing at end-of-life | Whole-building aggregation — use the EN 15978 Whole-Building LCA Calculator |
| C4 final disposal (engineered panels and wood-fibre only) | Sequestration permanence / carbon-credit claims — outside EN 15804 |
| Module D reuse/recovery credit (separate line) | Forest land-use-change emissions — see the FLAG Emissions Calculator |
The Biogenic Carbon Problem — Why Timber Is Reported Differently
Biogenic carbon is the single concept that separates a correct timber inventory from a misleading one. Under EN 15804+A2, the GWP of a product is reported as the sum of three terms: fossil, biogenic, and land-use-and-land-use-change. The identity is exact:
GWPtotal = GWPfossil + GWPbiogenic + GWPluluc
For a cubic metre of CLT, the EN 15804 A1–A3 total is about −660 kg CO₂e, of which the biogenic term is roughly −754 kg CO₂e. The fossil-plus-land-use remainder is therefore positive — close to +94 kg CO₂e — representing the real fossil energy used to harvest, dry, glue, and press the timber. The product looks net-negative only because the biogenic uptake outweighs the fossil processing energy at this single stage.
The biogenic carbon recorded as negative at A1–A3 is released again at module C when the timber is incinerated or decays. Treating the A1–A3 figure as a permanent reduction double-counts a carbon flow that the life cycle later reverses. Report the A–C total; disclose the biogenic term separately so reviewers can see what is sequestered versus what is genuinely avoided.
The Unit Trap on the Biogenic Field
One technical subtlety matters for anyone reading the raw EPD or factor data: the biogenic carbon value in the underlying dataset is the EN 15804+A2 GWPbiogenic indicator expressed in kg CO₂e per m³, even where a field label abbreviates it as “kg C-biogenic”. It is already a CO₂-equivalent quantity — do not multiply it by 44/12 or by a 3.667 carbon-to-CO₂ factor a second time. Doing so inflates the biogenic term by a factor of nearly four and is one of the errors in the audit checklist below.
Permanence and the 100-Year Question
EN 15804 and ISO 14067 permit biogenic carbon storage to be credited only where storage persists — the common reference period is 100 years. A timber element reused or kept in service beyond that horizon can support a storage claim; one incinerated after a 30-year building life cannot. This calculator does not award a storage credit by default: it reports the biogenic term transparently and leaves the permanence judgement to your assessment methodology, consistent with the conservative EN 15804 default.
CLT, Glulam, Softwood and Hardwood — Factors Side by Side
All factors below are ÖKOBAUDAT 2024 datasets prepared to EN 15804+A2 / EF 3.1, at AR5 GWP-100, declared per cubic metre, and classified as Scope 3 Category 2 for the asset owner. Values are sourced from MasterBrain v2025.80.
| Product | A1–A3 | C3 | C4 | Module D | Biogenic (in A1–A3) | Density (kg/m³) |
|---|---|---|---|---|---|---|
| CLT (cross-laminated timber) | −660.1 | 753.4 | 0 | −409.9 | −753.8 | 470 |
| Glulam | −608.4 | 753.4 | 0 | −409.9 | −753.2 | 470 |
| Softwood (sawn) | −629.4 | 863.0 | — | −274.8 | −845.9 | 529 |
| Hardwood (sawn) | −1019.3 | 1142.0 | — | −382.3 | −1119.8 | 716 |
| LVL (laminated veneer lumber) | −400.9 | 785.0 | — | −199.9 | −763.3 | 465 |
| OSB (oriented strand board) | −639.3 | 983.2 | — | −165.5 | −986.7 | 600 |
| Plywood | −660.1 | 753.4 | 0 | −409.9 | −753.8 | 470 |
| Cellulose insulation | −72.72 | 84.14 | — | −24.65 | −82.47 | 45 |
| Wood-fibre insulation | −253.4 | 322.4 | 0 | −236.0 | (none) | 200 |
| Straw insulation | −98.03 | 148.12 | — | −54.35 | −145.12 | 100 |
| Expanded cork | −85.08 | 128.32 | — | −24.98 | −126.48 | 80 |
| Hemp-fibre insulation | +58.26 | 75.48 | — | −19.10 | −5.50 | 38 |
| Flax-fibre insulation | +64.07 | 76.07 | — | −19.10 | +0.33 | 38 |
All values kg CO₂e/m³ except density. “—” indicates the dataset carries no C4 row (no value is invented for it). C4 exists only for CLT, glulam, plywood, and wood-fibre in this dataset. Source: ÖKOBAUDAT 2024 (EN 15804+A2 / EF 3.1), AR5 GWP-100, via MasterBrain v2025.80.
The Declared Unit Is per m³ — Convert Mass via Density
Every factor here is declared per cubic metre, not per kilogram. To convert a mass quantity (for example a delivered tonnage on a purchase order) to volume, divide by the product density in the final column. A 12-tonne delivery of CLT at 470 kg/m³ is 25.5 m³, not 12 units of anything — entering mass where the calculator expects volume is a common and large error. The calculator handles the conversion when you select the input unit; spreadsheet-based assessments must do it explicitly.
Engineered vs Sawn — Why Processing Adds Carbon
Sawn hardwood shows the most negative A1–A3 figure (−1019.3 kg CO₂e/m³) largely because of its high density (716 kg/m³) — more wood mass means more biogenic carbon per cubic metre. Engineered products carry more fossil processing energy: LVL and OSB require veneer peeling or strand drying plus resin and pressing, which is why LVL at −400.9 is markedly less negative than sawn softwood at −629.4 despite similar density. The bar chart below contrasts the A1–A3 product-stage figure across the structural range.
A1–A3 product-stage embodied carbon, kg CO₂e/m³ (more negative = more biogenic carbon held at the gate). Bars scaled to the most-negative value. Not a whole-life ranking — see Module C.
Module C and Module D — End-of-Life and the Reuse Credit
The product stage tells only part of the story. What happens to the timber at end-of-life — and what credit, if any, is claimed beyond the system boundary — determines the honest whole-life figure.
C3 and C4 — The Stored Carbon Comes Back
Module C3 (waste processing) is positive for every timber product because end-of-life treatment — incineration, or aerobic decay — releases the biogenic carbon that A1–A3 recorded as negative. For CLT, C3 of +753.4 kg CO₂e/m³ broadly offsets the −660.1 product stage, leaving a small positive A–C total per cubic metre. Module C4 (final disposal to landfill) is present only for the engineered-panel and wood-fibre rows in this dataset and is zero in those rows; sawn softwood, hardwood, LVL, OSB, and the agri-fibre insulants carry no C4 line at all.
Module D — Reported, Never Netted
Module D captures benefits beyond the system boundary: the avoided burden when timber is reused, recycled, or recovered for energy. It is reported as a separate line under EN 15804+A2, EN 15978, and RICS WLCA. The reason it is never added into A–C is integrity: Module D represents a benefit in a different system (a future product, or a displaced energy source), not a reduction in the assessed building’s own footprint. Netting it in would let an end-of-life assumption flatter the asset’s reported carbon.
Landfill (C4)
Biogenic carbon stays largely locked in anaerobic conditions, but methane risk and no energy recovery. Module D credit is minimal. Lowest beyond-boundary benefit of the three routes.
Incineration with energy recovery
Releases the stored biogenic carbon at C3, but displaces fossil energy — yielding the Module D recovery credit (for CLT, −409.9 kg CO₂e/m³). Reported separately, never inside A–C.
Reuse
Defers the C3 release entirely and supports a biogenic-storage claim if permanence holds. The strongest whole-life outcome, but conditional on the timber’s actual second life being documented.
Bio-Based Is Not Always Carbon-Negative — Hemp and Flax
The assumption that any plant-derived material is automatically carbon-negative is wrong, and the factor table proves it. Hemp-fibre insulation (+58.26 kg CO₂e/m³) and flax-fibre insulation (+64.07 kg CO₂e/m³) are net-positive at A1–A3. Their biogenic uptake is small in absolute terms — hemp’s biogenic term is only −5.50 kg CO₂e/m³ and flax’s is fractionally positive at +0.33 — because these are low-density products (38 kg/m³) holding little carbon per cubic metre, while the processing energy to ret, decorticate, and bond the fibres is comparatively high.
A “natural”, “bio-based”, or “renewable” descriptor says nothing about embodied carbon. Cork (−85.08), straw (−98.03), and cellulose (−72.72) are net-negative at A1–A3; hemp and flax fibre are net-positive. When the carbon performance of the insulation layer matters to a specification, compare the EN 15804 A1–A3 and A–C figures directly rather than relying on the material’s bio-based provenance.
This does not make hemp or flax poor choices — both have moisture-buffering and health attributes that fall outside a carbon metric, and both still earn a small Module D recovery credit (−19.10 kg CO₂e/m³). It makes the point that embodied-carbon decisions belong to the EPD figures, not to a material’s general reputation.
Timber vs Concrete vs Steel — The Substitution Case
The structural case for timber rests on substitution: replacing a high-carbon frame material with one whose product stage is net-negative. The contrast is real, but it must be made on a like-for-like functional basis, not a naïve per-cubic-metre or per-kilogram comparison.
A cubic metre of CLT and a cubic metre of concrete do not perform the same structural job — a timber floor plate and a concrete slab spanning the same bay carry different volumes. Comparing −660 kg CO₂e/m³ (CLT) against +196 kg CO₂e/m³ (ready-mix C30/37) without normalising to the same load, span, and fire/acoustic performance overstates the timber advantage. Always substitute on a defined functional unit.
With that caveat stated, the directional product-stage contrast is stark. For a like-for-like structural comparison, run the matching materials through their dedicated calculators and compare A–C totals on a common functional unit:
Timber (this calculator)
A1–A3 net-negative; A–C near-neutral after end-of-life biogenic release. Module D recovery credit reported separately. Best product-stage profile of the three frame materials.
Concrete
No biogenic term; A1–A3 unambiguously positive (ready-mix C30/37 ≈ +196 kg CO₂e/m³). SCM substitution (GGBS, fly ash, LC3) is the main lever — model it in the concrete calculator.
Steel & aluminium
No biogenic term; recycled-content route drives most of the variance. Primary vs recycled is the decisive factor — model it in the steel & aluminium calculator.
For a building-level substitution study that aggregates all three across the full A–D module set on a consistent boundary, use the EN 15978 Whole-Building LCA Calculator rather than comparing single-material outputs by hand.
Worked Example — CLT-and-Glulam Floor Frame
This example takes the calculator’s shipped default — a floor frame of 50 m³ CLT panel and 10 m³ glulam beams — through the full module chain. All factors are ÖKOBAUDAT 2024 via MasterBrain v2025.80.
EN 15804, EN 15978 and RICS — Which Standard Governs What
Three standards govern timber embodied carbon at different scales. Understanding which applies prevents the common error of quoting a product EPD figure as if it were a building result.
| Standard | Scale | What it governs |
|---|---|---|
| EN 15804+A2 | Product | Core rules for construction-product EPDs — the module structure (A–D), the biogenic/fossil/luluc GWP split, and the declared-unit conventions this calculator uses. |
| EN 15978 | Whole building | Aggregates product EPDs across all modules and elements into a building-level assessment, adding A4–A5 construction and B1–B7 use-stage. |
| RICS WLCA | Whole building (practice) | The UK practice methodology layered on EN 15978 — defines reporting scope, benchmarks, and how Module D is presented separately in a whole-life assessment. |
| ISO 14067 | Product (carbon footprint) | Product carbon-footprint quantification, including biogenic carbon and storage-permanence rules consistent with the EN 15804 treatment. |
EPD Module Map
An EN 15804 EPD reports up to four module groups. This calculator covers the material-intrinsic ones: A1–A3 (product), C3–C4 (end-of-life), and D (beyond boundary). The construction stage (A4–A5) and use stage (B1–B7) are project- and building-specific and belong to a whole-building assessment under EN 15978, not to a single-material calculation.
Audit Checklist — Seven Common Timber Embodied-Carbon Errors
Embodied-carbon assessments are increasingly subject to third-party review under EN 15978, RICS WLCA, or ISO 14064 verification. The seven items below are the most frequent sources of restated timber figures.
Data Sources, Factor Provenance and Uncertainty
The complete underlying reference — every factor in this section, versioned with full source provenance and downloadable as CSV with a citable Zenodo DOI — is published as the Ökobaudat embodied carbon factors dataset.
Factor Provenance
All embodied-carbon factors are sourced from MasterBrain v2025.80 and traceable to their underlying datasets:
- Timber and bio-insulation A1–A3, C3, C4, D factors — ÖKOBAUDAT 2024, the German federal construction-materials EPD database, prepared to EN 15804+A2 / EF 3.1, declared per m³, AR5 GWP-100.
- Module structure and biogenic/fossil/luluc split — EN 15804+A2 core EPD rules.
- Whole-building aggregation rules — EN 15978 and RICS Whole Life Carbon Assessment.
- Cross-reference embodied-carbon dataset — the open ICE database provides an independent UK-focused check on the ÖKOBAUDAT figures where products overlap.
Uncertainty
EPD-derived factors are dataset-specific average values, not measured site data. Generic ÖKOBAUDAT timber datasets typically carry an indicative uncertainty in the ±20–30% range at A1–A3, driven mainly by forestry region, drying energy source, and (for engineered products) resin content and pressing energy. Where a product-specific EPD exists for the actual supplied material, it supersedes the generic factor and tightens the estimate. Treat the calculator output as an EN 15804-consistent baseline, to be refined with supplier EPDs for material categories that dominate the assessment.
Version and Update Schedule
Factor data is sourced from MasterBrain v2025.80 (June 2026). ÖKOBAUDAT is revised periodically as new EPDs are published and as the underlying EF background dataset updates; the data version badge in the calculator footer reflects the live MasterBrain version in use.
Frequently Asked Questions
At the product stage (A1–A3) timber shows a net-negative embodied-carbon figure — about −660 kg CO₂e/m³ for CLT — because EN 15804 counts the biogenic carbon the tree absorbed while growing. But that stored carbon is released again at end-of-life (module C) when the timber is incinerated or decays. The cradle-to-grave A–C figure is therefore near-neutral, not negative. Timber is low-carbon relative to concrete and steel, but a negative A1–A3 number is not a carbon-negative building.
Cross-laminated timber has an A1–A3 product-stage embodied carbon of about −660 kg CO₂e/m³ (ÖKOBAUDAT 2024, EN 15804+A2, AR5 GWP-100). Its C3 end-of-life figure is about +753 kg CO₂e/m³, so the cradle-to-grave A–C total is a small positive per cubic metre once the stored biogenic carbon is released. The Module D reuse/recovery credit (about −410 kg CO₂e/m³) is reported separately and not added into A–C.
EN 15804+A2 splits a product’s GWP into fossil, biogenic, and land-use terms: GWPtotal = GWPfossil + GWPbiogenic + GWPluluc. The split matters because biogenic carbon is a temporary store that reverses at end-of-life, whereas fossil emissions are a permanent addition to the atmosphere. Reporting them separately lets a reviewer see how much of a timber product’s negative product-stage figure is sequestered carbon (later released) versus a genuine fossil reduction.
Module D records benefits beyond the assessed system’s boundary — the avoided burden when timber is reused, recycled, or recovered for energy in a future product or process. Because that benefit accrues to a different system, EN 15804+A2, EN 15978, and RICS WLCA all require it to be reported on a separate line rather than netted into the cradle-to-grave A–C figure. Netting it in would let an end-of-life assumption reduce the assessed building’s own reported footprint.
No — both are net-positive at A1–A3. Hemp-fibre insulation is about +58 kg CO₂e/m³ and flax-fibre about +64 kg CO₂e/m³. They are low-density products (around 38 kg/m³), so they hold little biogenic carbon per cubic metre while the energy to process and bond the fibres is comparatively high. Cork, straw, and cellulose insulation, by contrast, are net-negative at A1–A3. Bio-based provenance alone does not determine embodied carbon — the EN 15804 figures do.
Divide the per-m³ factor by the product density. CLT at −660.1 kg CO₂e/m³ and 470 kg/m³ works out to about −1.40 kg CO₂e/kg. To go the other way — converting a delivered tonnage to the volume the calculator expects — divide the mass by the density: a 12-tonne CLT delivery is 12,000 ÷ 470 ≈ 25.5 m³. Entering mass directly against a per-m³ factor mis-scales the result by the density value, which is one of the most common errors in spreadsheet-based assessments.
They operate at different scales. EN 15804+A2 governs individual product EPDs and the module/biogenic conventions this calculator applies. EN 15978 aggregates those products into a whole-building assessment, adding construction (A4–A5) and use (B1–B7) stages. RICS Whole Life Carbon Assessment is the UK practice methodology layered on EN 15978, defining reporting scope and benchmarks. Use this calculator for product-level timber figures, then roll them up under EN 15978 or RICS WLCA for a building-level result.
Methodology Notes and Limitations
EPD-average factors, not site data. All values are ÖKOBAUDAT 2024 generic datasets. Where a product-specific EPD exists for the supplied material, it supersedes the generic factor and should be used for any category that dominates the assessment.
Declared unit is per m³. Convert mass inputs to volume using the published density before applying a factor. The calculator handles this when the input unit is selected; spreadsheet assessments must do it explicitly.
Biogenic value is already CO₂e. The biogenic carbon field is the EN 15804 GWPbiogenic indicator in kg CO₂e/m³, notwithstanding a “kg C-biogenic” label on the raw field. Do not re-apply a carbon-to-CO₂ conversion.
No default storage credit. The calculator does not award a biogenic-storage credit by default, consistent with the conservative EN 15804 treatment of permanence. Storage claims require a documented permanence basis (commonly 100 years) and belong to your assessment methodology.
Material-intrinsic modules only. A1–A3, C3, C4, and D are covered. Construction (A4–A5) and use (B1–B7) stages are project- and building-specific and belong to a whole-building assessment under EN 15978.
C4 coverage is partial by dataset. A C4 row exists only for CLT, glulam, plywood, and wood-fibre in this dataset (value zero in each). No C4 figure is assumed for the products that lack the row.
You have a product-level timber and bio-materials embodied-carbon figure across A1–A3, C3, C4, and Module D. The next steps depend on whether you are comparing materials or aggregating to a building.
Combine the timber result with the concrete and steel calculators on a common functional unit, then aggregate to a building-level figure with the EN 15978 Whole-Building LCA Calculator for a complete whole-life carbon assessment.
Timber is one material in a whole-life assessment. If you are running a substitution study, model the alternative frame materials in the Concrete & Cement and Steel & Aluminium embodied-carbon calculators and compare A–C totals on a defined functional unit. If you are ready to aggregate across the full element schedule, roll everything up in the EN 15978 Whole-Building LCA Calculator — each tool exports a module-resolved breakdown that combines cleanly.
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