Project Carbon Budgets

A project carbon budget is a target for total embodied carbon across all materials in a building project. It is typically expressed in kgCO₂e per square metre of gross internal floor area, making it comparable across projects of different sizes.

Think of it as analogous to a cost budget. It sets a ceiling that procurement decisions are measured against. Without one, there is no framework for evaluating whether a material choice moves the project in the right direction.

Carbon budgets are increasingly required by clients, planning authorities, and rating systems. The GLA in London requires whole-life carbon assessments for referable applications. BREEAM awards credits for demonstrated embodied carbon reduction. LETI and RIBA 2030 publish voluntary targets that many practices have adopted.

A carbon budget needs to be ambitious enough to drive better decisions but realistic enough to be achievable with available materials and construction methods.

Published benchmarks provide useful starting points, though they vary by building type, structural system, and assessment boundary.

On Matera, project-level carbon tracking works by aggregating the embodied carbon of every material added to your project's bill of materials. As you add products and quantities, the running total updates to show where the project stands against any target you have set.

Waste factors are applied to reflect realistic site quantities rather than net material. If your project specifies a 10% waste factor for timber, the carbon calculation uses the gross quantity (net × 1.10) rather than the theoretical minimum. This produces a more honest estimate.

The project summary breaks the total down by material, showing each item's contribution, data quality, and lifecycle scope. This makes it easy to identify which materials are driving the total and where the biggest reduction opportunities exist.

When a project carbon summary shows a total like '420 kgCO₂e/m² (12 of 15 materials included)', it means three materials could not be included in the calculation. This is not a bug - it is a design choice to be transparent about what is and is not in the number.

Materials may be excluded for several reasons: no product has been selected yet, the selected product has no carbon data, the quantity has not been entered, the units are incompatible, or the carbon data scope does not match the project's reporting boundary.

Each excluded item is listed with its specific reason, so you know exactly what to address. The goal is to progressively reduce exclusions as procurement advances - from early-stage estimates with many gaps to detailed specifications with verified data on most items.

Matera's CSV export produces a structured record of the project's carbon assessment. It includes material-level detail (product, quantity, carbon intensity, data quality tier, lifecycle scope, waste factor, and total contribution) as well as project-level summary data.

This export is designed to feed into the reporting workflows that sustainability consultants and project managers already use. It can support BREEAM Mat 01 evidence submissions, RIBA stage reports, and client sustainability updates.

The audit trail means every number is traceable back to its source. If a client or assessor asks why a figure was used, the export shows the product, the data quality tier, and the lifecycle scope - not just a bare number.

A carbon budget is a living document. It should be revisited at key project milestones.