Embodied Carbon Explained

Two types of building carbon

Every building has two carbon footprints. Operational carbon is the CO2 emitted by heating, cooling, lighting, and powering the building throughout its life. Embodied carbon is the CO2 emitted by making, transporting, installing, maintaining, and eventually demolishing the materials the building is made from.

For decades, the industry focused almost exclusively on operational carbon - better insulation, more efficient boilers, solar panels. That focus has been enormously successful. But as operational energy use falls towards zero (through Passivhaus, heat pumps, and grid decarbonisation), embodied carbon has become the dominant share of a building's total lifecycle emissions.

In a well-insulated new build today, embodied carbon can account for 50-70% of the building's total carbon footprint over 60 years. In a net zero energy building, it can be over 90%. This is why material selection has moved from a secondary concern to a primary design decision.

Operational carbon

Energy used to heat, cool, light, and power a building
Addressed through energy efficiency and renewables
Regulated by building standards (Part L, EPC)

Embodied carbon

Emissions from materials, transport, and construction
Addressed through material choices and design
Currently unregulated in most jurisdictions

By the numbers. Embodied carbon is 'locked in' at the point of construction. Once a material is manufactured and installed, its carbon impact cannot be undone. Operational carbon, by contrast, can be reduced over time through retrofitting and grid decarbonisation.

What counts as embodied carbon

Embodied carbon is measured through Lifecycle Assessment (LCA), typically reported in Environmental Product Declarations (EPDs). The key metric is Global Warming Potential (GWP), expressed in kilograms of CO2 equivalent per declared unit (e.g., per m², per kg, or per m³).

EPDs follow the lifecycle stages defined in EN 15804. The most commonly reported figure covers stages A1-A3: raw material extraction, transport to the factory, and manufacturing. This is called the 'cradle to gate' carbon footprint. But the full picture is broader - transport to site, construction waste, replacement cycles, and end-of-life processing all add to the total.

Topic	Detail
A1-A3 (Cradle to gate)	the manufacturing footprint. Always reported in EPDs and the most commonly compared figure.
A4 (Transport to site)	depends on distance and mode. Locally sourced materials often have a meaningful advantage here.
A5 (Construction)	site waste, cutting, fixing. Materials with high waste rates (e.g. plasterboard offcuts) carry a hidden carbon cost.
B4 (Replacement)	the carbon cost of replacing materials that do not last the building's design life. Critical for finishes, sealants, and shorter-life components.
C1-C4 (End of life)	demolition energy, transport to waste processing, and the emissions from disposal or recycling.
Module D (Reuse and recycling credit)	potential carbon savings if the material is recycled or reused. Reported separately because it is a future benefit, not a current impact.

Watch out. Be careful comparing EPDs with different lifecycle boundaries. An A1-A3 figure cannot be fairly compared with an A1-C4 whole-life figure.

Where carbon hides in construction

Not all materials contribute equally. Understanding where the carbon hotspots are helps you focus effort where it has the most impact.

Structure

Concrete, steel, and masonry in foundations, frames, and floors - typically 50–70% of total embodied carbon.

Envelope

Cladding, glazing, insulation, and roofing. Significant due to large surface areas.

Finishes

Flooring, plaster, paint, and ceiling systems. Lower per-unit carbon but high total area.

Services

MEP systems - ductwork, pipework, wiring. Often overlooked but can contribute 10–15%.

Tip. Start with structure. If you only have time to address one thing, reducing the embodied carbon of the structural frame will have more impact than optimising every other element combined.

How to compare products by embodied carbon

Comparing embodied carbon between products requires discipline. These rules will prevent the most common mistakes.

Topic	Detail
Same functional unit	compare the amount of material needed to perform the same function. 1 kg of timber vs 1 kg of steel is meaningless; a timber frame vs a steel frame designed to the same structural specification is meaningful.
Same lifecycle stages	if one EPD reports A1-A3 and another reports A1-A5, the numbers are not comparable without adjustment.
Same data quality	product-specific EPD data is more reliable than generic database averages. Compare like with like.
Include replacements	a material with higher upfront carbon but a 60-year lifespan may have lower lifetime carbon than a cheaper product replaced every 20 years.
Consider Module D cautiously	recycling credits are theoretical future benefits. They depend on recycling infrastructure and markets that may or may not exist in 60 years.
Check the carbon data date	manufacturing processes and energy mixes change. EPD data older than five years may no longer reflect current production.

Practical strategies to reduce embodied carbon

You do not need to be a carbon expert to make better choices. These strategies are practical and can be applied to most projects.

Topic	Detail
Build less	the lowest-carbon material is the one you do not use. Question whether every element is necessary. Can you refurbish instead of demolish and rebuild?
Build efficiently	reduce over-specification. Structural engineers often apply generous safety factors that increase material quantities. Value engineering with carbon as a criterion can yield significant savings.
Substitute materials	where performance allows, choose lower-carbon alternatives. Timber instead of steel for framing, GGBS concrete instead of CEM I, wood fibre instead of PIR insulation.
Verify claims	insist on product-specific EPDs rather than generic industry data. Generic or outdated averages can significantly misrepresent a product's actual carbon footprint.
Source locally	shorter transport distances reduce A4 emissions. This is particularly relevant for heavy, high-volume materials like aggregates and concrete.
Specify for longevity	choose durable materials that will not need replacing during the building's design life. Higher upfront carbon can mean lower lifetime carbon.
Design for disassembly	mechanical fixings instead of adhesives, modular construction, and material passports enable reuse at end of life, reducing the need for virgin materials in future projects.
Document trade-offs	record the reasoning behind material choices for future reference. Carbon is one factor among many, and the rationale should be transparent.

Common mistakes

Understanding what not to do is as important as knowing best practice. These are the most frequent errors in embodied carbon assessment.

Comparing products with different declared units (e.g., per kg vs per m²)
Using generic or outdated industry-average data instead of product-specific EPDs
Ignoring replacement cycles - a product that lasts 60 years has a different lifecycle impact than one requiring replacement every 20
Overlooking biogenic carbon claims without verifying the accounting methodology
Treating embodied carbon in isolation from other performance criteria like durability, fire safety, and cost

Using carbon data on Matera

Matera displays embodied carbon data where suppliers have provided it. Look for EPD-verified figures, which are third-party checked, versus self-declared data. Use the comparison features to evaluate materials side by side, and always check the functional unit and lifecycle stages before drawing conclusions.

The carbon data quality guide explains how to assess the reliability of the data you see. The project carbon budgets guide helps you set targets and track progress across a whole project.