Embodied Carbon Calculator

Embodied carbon is the greenhouse gas emissions from extracting, manufacturing and transporting a construction material, measured in kgCO2e (kilogrammes of carbon dioxide equivalent) per kg of material. The factors here are cradle-to-gate (life-cycle modules A1–A3 in EN 15978 / EN 15804) — raw-material supply, transport to factory, and manufacturing. Whole-life assessments (RICS, LETI, RIBA 2030) also add later stages such as on-site construction (A5), in-use (B) and end-of-life (C).

Softwood’s cradle-to-gate A1–A3 factor in the ICE Database v4.1 is about 0.31 kgCO2e/kg (the older v3 figure was ~0.263) — the fossil energy used to fell, saw and kiln-dry it. The carbon the tree absorbed during growth (~1.6 kgCO2e/kg of biogenic carbon) is real but, under EN 15804+A2, it is declared in a SEPARATE module rather than netted off the A1–A3 figure, because it is released again at end-of-life if the timber is burned or left to decompose. This calculator shows the positive A1–A3 value so timber is on the same basis as every other material; count the biogenic storage separately in a whole-life study.

Per kg (ICE v4.1 cradle-to-gate, primary/virgin where applicable): primary aluminium (~13.1), copper (~3.83), PIR insulation (~3.48), general structural steel (~1.55), mineral wool (~1.28), float glass (~0.85). Recycled aluminium drops to ~0.5 and recycled steel to ~0.45. Per m² of building, concrete often dominates the total despite its low per-kg factor (~0.15) because of the sheer volume used.

Key strategies: use timber instead of steel/concrete where structurally sensible, specify recycled-content materials (recycled aluminium and EAF steel are far lower), reduce overspecification, minimise waste, source locally to cut transport, use lower-carbon concrete mixes (GGBS or PFA cement replacement), and design for deconstruction and reuse.

The Inventory of Carbon and Energy (ICE) database, created at the University of Bath and maintained by Circular Ecology, is the most widely used source of embodied-carbon factors in the UK. The current version is v4.1, released 29 October 2025 (it updated GGBS, concrete and asphalt methodology). It gives cradle-to-gate kgCO2e/kg values for hundreds of materials. For procurement or compliance, use product-specific EPDs where available.

Yes — pick the “Timber (softwood)” material for a quick sawn-timber estimate, or use the Custom Factor field with a figure from a product EPD for engineered/mass timber such as CLT (cross-laminated timber) or glulam (glued-laminated timber). Mass timber A1–A3 factors are HIGHER than plain sawn softwood because of the structural adhesive and extra processing (pressing, planing, kiln-drying): published European EPD/ICE figures for glulam and CLT typically fall in roughly 0.3–0.5 kgCO2e/kg cradle-to-gate, versus around 0.07–0.31 kgCO2e/kg for sawn softwood. Because the exact value depends on the manufacturer, adhesive and recycled energy mix, the honest approach is to enter the specific A1–A3 figure from the product EPD or the IStructE/Arup mass-timber carbon-factor review rather than a single generic number.

No — the timber factors here are cradle-to-gate A1–A3 fossil-processing emissions only, on the same basis as concrete and steel, so the headline number is a positive (emitted) value. The biogenic carbon a growing tree absorbs (~1.6 kgCO2e per kg of wood) is real, but under EN 15804+A2 it is declared in a SEPARATE “climate change – biogenic” category rather than netted off A1–A3, and that stored carbon is treated as released again in the end-of-life modules (C1–C4). Over a sustainably-sourced product’s full life cycle the biogenic balance is net zero, so you should track stored carbon as its own line in a whole-life study, not subtract it from the A1–A3 result.

Usually yes for the structural frame, but compare like-for-like. Per kg, structural steel (~1.55 kgCO2e/kg ICE v4.1) and primary aluminium (~13.1) are far higher than any timber, while concrete is low per kg (~0.15) but used in huge volumes. Per m² of completed frame, peer-reviewed and IStructE studies generally show a mass-timber (CLT/glulam) structure with a markedly lower cradle-to-gate (A1–A3) embodied carbon than an equivalent steel or reinforced-concrete frame — One Click LCA, for example, reports a structural-timber office around 23% lower GWP than steel and ~14% lower than concrete across A1–A5 plus later stages. Use this tool per material/element and add the elements up; for a compliant building total follow the RICS Whole Life Carbon Assessment, 2nd edition (mandatory for RICS members from 1 July 2024) and product EPDs.