Material selection is one of the most visible parts of embodied carbon reduction. Concrete, steel, timber, masonry, insulation, façades, glazing, finishes and services can all influence the carbon profile of a building.

But low embodied carbon design is not simply a matter of choosing a list of “green materials”. A material that performs well in one project may not be the right choice in another. Structural requirements, durability, fire performance, moisture risk, maintenance, availability, cost, thermal performance and lifespan all matter.

The most useful approach is to understand where carbon is concentrated in the project and then review material choices in relation to design, compliance and long term building performance.

In Brief

Low embodied carbon materials are only useful when they suit the project.

Lower carbon materials may include lower carbon concrete mixes, efficient steel use, responsibly sourced timber, recycled content products, reused materials and durable systems with long service lives.

The right decision depends on the building type, structure, climate, compliance pathway, durability requirements and the available product data.

Embodied Carbon

Why materials matter in embodied carbon

Embodied carbon is shaped by the materials used to construct a building, the quantities required and the carbon intensity of those materials. A small quantity of a high impact material may matter less than a large quantity of a moderate impact material. This is why quantity and specification need to be reviewed together.

For many projects, carbon hotspots may be found in structure, concrete, steel, aluminium, façades, glazing, finishes and services. The pattern depends on the building type and the assessment scope.

An embodied carbon report can help identify which materials are driving impact before project teams focus on substitutions or specification changes.

Concrete

Lower carbon concrete needs careful specification.

Concrete can be a major contributor to embodied carbon, particularly in slabs, foundations, columns, cores and structural systems. This is partly because concrete is often used in large quantities.

Lower carbon concrete strategies may include reducing unnecessary concrete volume, reviewing structural efficiency, using supplementary cementitious materials where appropriate, specifying lower carbon mixes and considering project specific performance requirements.

Concrete decisions must still satisfy structural, durability, curing, fire, exposure and construction requirements. Lower carbon concrete is not just a product choice. It is a coordination issue between design, engineering, supply and construction.

Steel

Steel impact depends on quantity, source and design efficiency.

Steel can be carbon intensive, but it is also strong, durable and often structurally efficient. The embodied carbon outcome depends on how much steel is used, how efficiently it is designed, the production route, recycled content and the availability of product specific information.

Design strategies may include optimising spans, reducing over specification, coordinating structural systems early, using reused or recycled content steel where suitable and requesting Environmental Product Declarations where available.

The goal is not always to remove steel. The goal is to use the right amount of the right material for the building system.

Timber

Timber can support lower carbon design, but context matters.

Timber and engineered timber can be useful in lower embodied carbon construction, especially where they replace more carbon intensive materials and are sourced responsibly. Timber may be used in framing, flooring, wall systems, roof structures, mass timber systems, joinery and internal finishes.

However, timber still needs to be assessed against fire, moisture, durability, acoustic, structural, termite, maintenance and supply chain requirements. It should not be treated as automatically suitable for every building type.

A well considered timber strategy can reduce carbon, but it needs to be integrated into the project from the beginning.

Recycled Content

Recycled content can help, but it needs evidence.

Products with recycled content can sometimes reduce embodied carbon, particularly where they reduce demand for virgin materials or make use of existing material streams. Examples may include recycled steel content, recycled aluminium, recycled aggregates, recycled plastic products, carpet tiles, plasterboard content or reused building elements.

The carbon benefit depends on the product, manufacturing process, transport, quality, durability and the assumptions used in the assessment. Recycled content should be supported by supplier information, product data or Environmental Product Declarations where available.

Claims should be checked carefully. The strongest material decisions are supported by evidence, not just marketing language.

Reuse

The lowest carbon material may be the one already there.

Retaining existing buildings, structures and materials can sometimes avoid significant new embodied carbon. This is why adaptive reuse, refurbishment and careful demolition planning are becoming more important in low carbon design.

Existing structure, brickwork, steel, timber, façades, flooring, fixtures and other materials may be candidates for retention or reuse depending on condition, performance and compliance requirements.

Reuse must still be assessed for suitability, safety, durability and future performance, but it can be one of the most powerful embodied carbon strategies when it is feasible.

Envelope

Insulation and envelope materials need whole building review.

Insulation, membranes, cladding, linings and façade systems all have embodied carbon impacts. At the same time, they may influence operational performance, comfort, condensation risk, durability and compliance.

A lower carbon insulation product may still need to meet fire, moisture, thermal, acoustic and installation requirements. A façade material may carry a higher embodied carbon impact but contribute to durability or thermal performance depending on the design.

Envelope materials should be reviewed as part of a whole building approach rather than selected by carbon number alone.

Finishes

Finishes and fitout can matter, especially when they are replaced often.

Some finishes may seem minor compared with structure, but replacement cycles can change their lifecycle impact. Flooring, ceilings, plasterboard, joinery, paint, furniture, tenancy fitouts and internal linings may be replaced more often than structural elements.

Durable products, modular systems, reused materials, low waste installation, repairability and product data can all help improve the carbon profile of fitout decisions.

This is especially relevant in commercial buildings where fitout cycles may occur more frequently over the building’s life.

Evidence

Material decisions should be supported by data.

Lower carbon material selection is strongest when it is supported by reliable data. This may include Environmental Product Declarations, supplier information, verified product data, quantity information and clearly documented assumptions.

Without clear data, it can be difficult to know whether one material choice is actually better than another in the context of the project.

For practical inputs, read What Information Is Needed for an Embodied Carbon Report?.

Project Context

Why simple material lists can be misleading

Lists of low carbon materials can be useful as a starting point, but they can also oversimplify the issue. A material’s embodied carbon depends on quantity, source, manufacturing, transport, lifespan, maintenance, replacement and end of life assumptions.

A material with lower upfront carbon may not always be the better choice if it performs poorly, fails early, requires frequent replacement or creates compliance issues. Likewise, a material with a higher carbon intensity may be justified if it enables durability, structural efficiency or long service life.

The right question is not only “which material has the lowest carbon?”. It is “which material strategy gives this project the best long term outcome?”.

Summary

Low embodied carbon materials need careful, project specific review.

Lower carbon material choices may include lower carbon concrete, efficient steel use, responsible timber, recycled content products, reused materials, durable finishes and well considered envelope systems.

The best choices depend on the whole building. Structure, durability, compliance, availability, operational performance and lifecycle assumptions all need to be considered alongside embodied carbon.

Next Step

Need to understand which materials are driving embodied carbon in your project?

Certified Energy can review your project documentation and help identify embodied carbon hotspots across materials, structure, façade systems and construction scope.