Every building project carries an environmental cost.

Materials need to be extracted, manufactured, processed and transported before they ever reach a construction site. That means a significant part of a building's carbon footprint can exist before the building is even occupied.

This is where reclaimed materials become particularly interesting.

What is embodied carbon?

Embodied carbon refers to the greenhouse gas emissions associated with a building material across stages such as extraction, manufacture, transport, construction, maintenance and eventual end of life.

Unlike operational carbon, which relates to the energy used while a building is occupied, embodied carbon is largely tied to the materials and construction process itself.

This means that when a new brick, beam, tile or stone product is manufactured, some carbon has already been emitted before that material becomes part of a building.

The growing focus on whole-life carbon is encouraging the construction industry to consider these emissions more carefully.

Reuse changes the starting point

A reclaimed material begins its next use from a very different position to a newly manufactured product.

The material already exists.

The extraction and original manufacturing required to create it happened during its first life.

If that material can be recovered, prepared and reused in another project, some of the demand for producing an equivalent new product may potentially be avoided.

The important point is that reuse can provide an opportunity to extend the useful life of a product that has already been manufactured.

Whole-life carbon is changing how materials are assessed

The construction industry's understanding of carbon is increasingly moving beyond energy bills and heating efficiency.

RICS guidance on Whole Life Carbon Assessment considers emissions across a building's entire life cycle, including the manufacture of construction products, replacement, demolition, reuse, recycling and recovery.

This wider perspective makes decisions around material reuse increasingly relevant.

Instead of asking only how efficiently a completed building will operate, project teams are also being encouraged to think about where its materials came from and what happens to them later.

The scale of construction material use matters

Construction operates at an enormous scale.

That means the carbon and resource implications of material choices are repeated across thousands of individual projects.

Recovering one pallet of bricks or one batch of stone may seem small in isolation.

Repeated across refurbishment, redevelopment and demolition projects, however, greater material reuse could become much more significant.

Bricks show the difference between reuse and recycling

Bricks provide a useful example of why reuse can be different from recycling.

A brick removed carefully from a building can potentially be cleaned, sorted and reused in its original form.

If the same brick is crushed during demolition, it may still avoid landfill by becoming aggregate or another recycled material.

But the original product has been lost.

Reuse attempts to preserve more of the work, material and manufacturing already embodied within the finished brick.

Timber has an additional carbon story

Timber is particularly interesting because wood stores carbon absorbed during the growth of the tree.

Timber Development UK has argued that keeping timber within the built environment for longer can extend that period of carbon storage while also reducing pressure on virgin timber resources.

Research into reclaimed timber in the UK has also found that the main barriers to reuse are often practical rather than purely technical.

These practical issues can all affect whether reusable wood actually reaches another project.

Stone can remain useful for generations

Natural stone can also have an exceptionally long useful life.

Paving, walling stone, architectural pieces and other products may remain suitable for reuse long after the original building or landscape has changed.

Where existing stone can be recovered and reused appropriately, it provides an alternative to immediately extracting and processing new material.

Its durability is one of the reasons stone can move through multiple uses over a very long period.

Deconstruction can preserve more material value

The carbon opportunity around reclaimed materials often begins before demolition.

Traditional demolition can make material recovery difficult if products are broken, contaminated or mixed together during the process.

Deconstruction takes a more selective approach by identifying potentially reusable materials before work begins and removing them carefully where practical.

Pre-demolition audits can support this process by recording the materials inside a building and identifying possible reuse opportunities.

The example shows why understanding what exists inside a building before demolition can be so valuable.

Transport still matters

Reclaimed does not automatically mean low carbon.

A material that requires extensive transport, specialist processing or repeated handling can still carry a significant environmental cost.

Heavy materials such as stone are particularly sensitive to transport distance because moving them requires energy.

This means local and regional reuse can be especially attractive where suitable stock is available nearby.

Preparation can create additional impacts

Recovered materials may also require work before they are ready for another project.

These processes can involve labour, energy and cost.

They do not remove the potential environmental benefit of reuse, but they are part of the overall calculation.

The condition of the material matters

A reclaimed material only provides value if it remains suitable for its next use.

Damaged, contaminated or heavily deteriorated products may not be appropriate for reuse.

Structural materials may require assessment, testing or grading before they can safely be specified.

The aim should therefore not be to reuse every material regardless of condition.

It is to identify products that still have useful life remaining and preserve that value wherever practical.

Better information could improve carbon decisions

One of the difficulties with reclaimed products is that information can be inconsistent.

A buyer may know that reclaimed stock exists but have little information about its dimensions, quantity, location, condition or previous use.

That uncertainty can make professionals more likely to select a standard new product instead.

Reuse can also reduce demand for new resources

The carbon argument is only one part of the environmental case for reclamation.

Reusing existing products can also reduce the immediate need for new raw materials.

This is the basic principle behind a more circular approach to construction: extract as much useful life as possible from materials that already exist.

Reclaimed materials are not a complete solution

It is important not to overstate the role of reclamation.

The UK construction industry will continue to require large quantities of new material.

Reclaimed stock can be inconsistent, quantities can be limited and some products will simply not meet the requirements of a particular project.

Reuse should therefore be considered one part of a wider strategy.