Comparing Materials by Carbon

Two insulation products can both claim a carbon figure and still be impossible to compare directly. One might report in kgCO₂e per kilogram, the other per square metre at a specific thickness. One covers raw material extraction through to factory gate (A1–A3), the other includes transport and installation (A1–A5). One figure comes from a third-party verified EPD, the other from an industry benchmark database.

Without aligning these variables, a lower number does not necessarily mean a lower-carbon product. It might just mean a different measurement basis.

This guide walks through the three alignment steps that make carbon comparison meaningful: scope, units, and data quality.

Lifecycle scope defines which stages of a product's life are included in the carbon figure. The most common reporting boundary is A1–A3, covering raw material supply, transport to factory, and manufacturing. This is the product stage - sometimes called cradle-to-gate.

Matera uses A1–A3 as its primary reporting scope because it is the most consistently available across product types and the stage where material selection has the most direct influence.

Problems arise when one product reports A1–A3 and another reports A1–A5 (which adds transport to site and construction waste). The A1–A5 figure will always be higher, but that does not mean the product has higher production-stage carbon. You are comparing different things.

Declared units vary between products and product categories. Structural timber is typically reported per cubic metre. Insulation is often per square metre at a stated thickness. Paints and coatings may be per litre or per square metre of coverage.

To compare two products that serve the same function, you need to express their carbon in the same functional unit. This often means converting using density (to go between kg and m³) or thickness (to go between m² and m³).

Matera performs this normalisation automatically where the necessary conversion factors are available. When it does, it shows the assumptions used - such as the density or thickness applied - so you can judge whether the conversion is reasonable for your application.

Not all carbon numbers carry the same weight. A product-specific EPD verified by an independent programme operator is the strongest evidence. A generic industry benchmark is useful for early-stage estimates but should not be treated as definitive.

Matera classifies carbon data into quality tiers so you can see at a glance how much confidence to place in each figure.

The compare table on Matera shows carbon data alongside price, certifications, and other product attributes. Each carbon value is accompanied by its lifecycle scope and a data quality badge, so you can see at a glance whether two products are genuinely comparable.

When a scope mismatch exists between products in the same comparison, Matera flags it with a warning. When normalisation has been applied, the basis and assumptions are shown. When data quality differs significantly, the badges make this visible without requiring you to dig into the source documents.

The goal is not to reduce material selection to a single carbon number. It is to make sure that when carbon does influence a decision, the comparison is fair and the limitations are transparent.

Even with scope, units, and data quality aligned, there are pitfalls that can distort a carbon comparison.