What lifecycle stages does this cover?

Stages A1 to A3 only — raw material supply, transport to the factory, and manufacturing. This cradle-to-gate boundary is the most common basis for early-design embodied-carbon comparison. It excludes construction (A4-A5), use (B), and end-of-life (C).

Where do the emission factors come from?

From the Inventory of Carbon and Energy (ICE) database version 3.0 by Circular Ecology, a widely used UK reference for embodied carbon of construction materials, expressed in kg CO2e per kilogram of material.

Why does concrete dominate so many buildings?

Concrete has a modest factor per kilogram, around 0.1 to 0.16, but buildings use enormous quantities of it, so it usually makes up the largest single share of structural embodied carbon. Cement production is the main driver; replacing some cement with GGBS or fly ash lowers it.

How does timber compare?

Timber has a low cradle-to-gate factor — often well under 0.5 kg CO2e per kg — and also stores biogenic carbon while it stands, which some assessments credit separately. Substituting timber for steel or concrete in a frame can sharply cut embodied carbon, subject to structural and fire requirements.

How do I compare against RIBA 2030 targets?

RIBA targets are expressed per square metre of floor area (for example under 625 kg CO2e per square metre for offices). Divide your total embodied carbon by the gross internal floor area to get the per-square-metre figure, then compare to the relevant target band.

Embodied Carbon Calculator (Building Materials)

Embodied carbon — the emissions locked into a building’s materials before it is even used — now rivals operational energy as a target for the construction sector. This calculator totals the cradle-to-gate embodied carbon of a material schedule using the widely cited ICE database, so design options can be compared quickly.

How it works

Each material’s contribution is its mass times its embodied carbon factor, and the building total is the sum:

material CO2e = mass (kg) × ICE factor (kg CO2e per kg)
total = Σ material CO2e over all materials
per m2 = total / gross internal floor area

The factors cover lifecycle stages A1 to A3 (cradle-to-gate), the standard boundary for early-design comparison, so two structural schemes can be weighed on a consistent basis before detailed assessment.

Example and tips

A small structural frame using 50 tonnes of concrete (factor about 0.13) and 5 tonnes of reinforcing steel (about 1.99) carries roughly 6.5 plus 10 tonnes of CO2e — and the steel, though a tenth of the mass, contributes more than the concrete. The largest reductions usually come from cutting cement content, using recycled-content or electric-arc-furnace steel, and substituting timber where structurally viable. Always divide the total by floor area to benchmark against RIBA per-square-metre targets.