Embodied Carbon in Buildings

What embodied carbon is

Embodied and operational carbon

A building's environmental impact includes emissions associated with both its construction and its operation.

Operational carbon refers to greenhouse gas emissions associated with operating the building, including energy used for heating, cooling, hot water, lighting and appliances.

Embodied carbon refers to greenhouse gas emissions associated with materials and construction processes across the building's lifecycle. These emissions are commonly expressed as carbon dioxide equivalent, which allows different greenhouse gases to be considered using a common measure.

Upfront embodied carbon generally includes:

• Raw material extraction and processing
• Product manufacturing
• Transport to the construction site
• Construction and installation activities

Whole of life embodied carbon can also include:

• Maintenance and repair
• Material and equipment replacement
• Refurbishment
• Demolition or deconstruction
• Transport and waste processing
• Disposal, reuse or recycling

Upfront emissions occur before occupation, but embodied emissions are not necessarily incurred only once. Later work on the building can add further embodied emissions over time.

Why it matters

As buildings and electricity systems change, operational emissions may fall relative to the emissions associated with materials and construction. The balance differs between buildings and depends on the energy supply, building performance, materials, maintenance, replacement cycles and the period being assessed.

Embodied carbon is therefore worth considering alongside operational energy, comfort, durability, maintenance and the practical needs of the people using the building.

It should not be treated as the only measure of whether a building or material is environmentally preferable.

Why material comparisons require evidence

Some building products can involve energy intensive extraction and manufacturing processes. However, the embodied carbon of a completed building depends on more than the name of the material.

A meaningful comparison considers:

• The quantity used
• Product composition
• Manufacturing process
• Energy sources used in production
• Transport
• Construction method
• Durability and maintenance
• Replacement requirements
• Reuse, recycling and disposal assumptions
• The lifecycle stages included in the assessment

Steel, aluminium, concrete, masonry and timber can have very different results depending on the product, supplier, design and assessment method. No material category should be presented as universally highest or lowest without suitable evidence.

Comparing suitable alternatives

Reducing material quantities, avoiding unnecessary construction, retaining suitable existing elements, selecting products with lower verified emissions and designing for durability may all reduce embodied carbon.

Reused or reclaimed materials may avoid some emissions associated with manufacturing new products. Their condition, processing, transport, treatment, suitability and expected service life still need to be considered.

Timber may compare favourably with other structural options in some projects, but the result depends on forestry practices, processing, treatment, transport, durability, replacement and the method used to account for stored biogenic carbon and end of life outcomes.

The appropriate comparison is between products and systems capable of performing the same required function within the particular building.

Environmental Product Declarations

An Environmental Product Declaration, known as an EPD, provides independently verified environmental information about a product using an established assessment method.

An EPD does not automatically mean that a product has low embodied carbon. It provides information that may help designers and assessors compare appropriate products where the declared scope, functional performance and lifecycle assumptions are compatible.

For a new build or substantial renovation, ask whether product specific EPDs or recognised emission factors have been used in the assessment.

What it means for buyers

How it may influence a property decision

Embodied carbon will not carry the same weight for every buyer. Location, budget, suitability, building condition, planning considerations, maintenance and ongoing costs will often remain more immediate concerns.

For buyers interested in the broader environmental impact of a property, embodied carbon can provide another useful perspective. It is particularly relevant when comparing renovation with demolition, commissioning a new build or undertaking substantial construction work.

It should be considered alongside operational performance, durability, adaptation, maintenance and how well the property meets the buyer's needs.

Retaining and improving an existing home

Retaining suitable parts of an existing building may avoid some upfront emissions associated with demolition and new construction.

The existing structure has already been produced, but future renovation, maintenance, replacement and eventual end of life work can still create additional embodied emissions.

Whether retention produces a better whole of life result depends on:

• The condition of the building
• The extent of work required
• Materials added or removed
• Waste generated
• Expected service life
• Future maintenance and replacement
• Operational performance after the work
• The period and scope of the assessment

Comparing renovation and replacement

Some buildings can be adapted successfully, while others may require extensive work to meet the buyer's needs or address condition, design and performance issues.

A useful comparison considers the retained structure and proposed renovation against demolition and replacement using the same study period and assessment boundaries.

The decision will also involve planning, construction, financial, functional and personal considerations that an embodied carbon assessment does not resolve on its own.

For buyers commissioning new builds

Embodied carbon can be considered during early design by comparing suitable structural systems, reducing unnecessary material use, selecting products with verified environmental information and designing for durability, maintenance and future adaptation.

Rather than prescribing timber, steel, concrete or another material in isolation, ask the architect, designer or lifecycle assessment professional to compare appropriate options for the building.

Useful questions include:

• Has an upfront or whole of life embodied carbon assessment been undertaken?
• What lifecycle stages are included?
• Which material quantities and emission factors were used?
• Were product specific Environmental Product Declarations available?
• What assumptions were made about transport, maintenance, replacement and end of life?
• Were suitable lower emission alternatives considered?

Looking beyond broad sustainability claims

A property may be marketed as sustainable because it has solar panels, an energy rating or particular materials. Those features do not establish the embodied carbon of the building.

Where an embodied carbon claim is made, ask:

• What was measured?
• Which lifecycle stages were included?
• Who completed the assessment?
• What data and assumptions were used?
• Is a report, estimate or certified rating available?

Local context

Material decisions in the Noosa region

Material decisions should respond to the property, climate, site conditions, construction method and expected maintenance.

In the Noosa region, coastal exposure, humidity, termites, bushfire requirements, transport distances and access may be relevant for some properties. A material with lower reported production emissions may not provide the better whole of life result if it is unsuitable for the site, requires frequent replacement or creates additional maintenance.

For a new build or substantial renovation, durability and appropriate detailing should be considered alongside embodied carbon. The environmental result depends on the complete building and its expected life rather than one material label.

Assessment tools in Australia

Australia now has recognised tools and data for assessing embodied carbon.

The National Australian Built Environment Rating System, known as NABERS, provides an Embodied Carbon rating tool for eligible new buildings and partial rebuilds. Certified ratings must be completed by an accredited NABERS assessor and use the applicable rules.

NABERS also publishes a national material emission factors database that may be used where suitable product specific Environmental Product Declarations are not available.

The certified NABERS Embodied Carbon rating is not currently available for Class 1 detached houses. Eligibility, scope and suitability depend on the project, so buyers considering an assessment should confirm the current NABERS requirements and obtain advice from an appropriately qualified professional.

What to verify

Questions for an embodied carbon claim