Embodied energy

The embodied energy of a building is a calculation of all the energy used to produce the materials that make up the building. It includes the energy used in mining, manufacturing and transporting the materials, as well as the services in the economy that support these processes.

The total embodied energy of a building is the total energy needed for:

• production of all the materials used in the initial construction (initial embodied energy)
• production of all the materials used in repairs or renovations over the life of the building (recurrent embodied energy)
• transport of materials to site
• energy used on-site during construction, repairs or renovations.

The choice of materials and construction methods can significantly change the amount of energy embodied in a building, because embodied energy varies enormously between materials. Different materials also have different capacities to be reused or recycled, which can help recover the embodied energy at the end of a building’s life.

Source: Murray Hall

Embodied energy and operational energy

Embodied energy is just one part of the energy use of a building. The other is operational energy – the energy that is used to run the home, including for lighting, appliances, heating, and cooling.

When you are buying, building, or renovating a home, it is worthwhile considering both the embodied energy of the materials and how they affect the operational energy use. Comparing materials based on their lifecycle energy performance will consider initial and recurrent embodied energy as well as their operational energy use. The Low Energy Building Assembly Selector can be used for this purpose.

For example, large amounts of thermal mass (for example, concrete), which is high in embodied energy, can significantly reduce operational heating and cooling needs in well-designed and insulated passive solar houses.

As buildings become more efficient in operation, the embodied energy proportion of the total energy use increases. This can be even more pronounced where additional materials (for example, insulation, double glazing, thermal mass) are added to the building to achieve operational energy savings.

For example, initial and recurrent embodied energy may represent just over 50% of the total life cycle energy of a typical brick veneer house over a life of 50 years – see following graph. The rest of the life cycle energy is taken up by operational energy. By contrast, the embodied energy proportion can approach 100% for zero-operational energy buildings, because less operational energy is required to run the home.

Source: Operational energy based on Weterings and Tustin (2017) and initial and recurrent embodied energy based on Crawford (2014) (average initial embodied energy of 13.4GJ/m², average recurrent embodied energy of 8GJ/m² for 50 years) and average floor area based on ABS/CommSec (2018) (new detached housing of 230.8m²).

Calculating embodied energy

Assessing the embodied energy of a material, component or whole building is a complex task. Every building is a complex combination of many materials, each with a production history and a contribution to the embodied energy of a building. Embodied energy can also vary for the same type of product because the efficiency of processes, sources of energy, and transport of materials can vary between manufacturers.

International standards have been developed for calculating the embodied energy of products (for example, ISO 14067:2018 Greenhouse gases – Carbon footprint of products – Requirements and guidelines for quantification). However, there are different methods used for the calculation. This means that some caution is required when using embodied energy values from different sources. For example, ‘hybrid analysis’ combines detailed data on processes used to manufacture particular products with background data of industry interactions. This method gives more comprehensive estimates of embodied energy than other methods as it captures a larger number of processes.

The calculation of embodied energy is often performed within a lifecycle assessment (LCA) framework (ISO 14040:2006 Environmental management — Life cycle assessment — Principles and framework). LCA considers a range of environmental impacts and is used for developing product labels and Environmental Product Declarations (EPD). International standards are available for developing EPDs of construction materials (refer to References and additional reading).

Your choice of materials should consider both the embodied energy of the materials and how the materials affect the design and operational energy of the building. In general:

• reduce materials with high embodied energy, unless they play a role in reducing operational energy; this may include sourcing local materials to reduce energy for transportation
• reuse existing materials, reducing the need for new materials
• choose new materials that have a high proportion of recycled content
• design for a long building life as well as disassembly for ease of reuse and recycling.

This general guidance may mean different material selections in different climates. Although materials with high thermal mass typically have high embodied energy, they can deliver operational energy savings when used in the right climates with the right passive design principles. However, used in the wrong climates or without regard for passive design principles, high thermal mass can add to the embodied energy of the building. It can also increase operational energy use and reduce thermal comfort.

Take care not to use materials that have more embodied energy than is required for the intended purpose. For example, there is little point in using a highly durable material with a high embodied energy, for example a floor covering, if the user intends to replace the flooring in a few years.

Photo: Maxiwall (© Big River Group)

Embodied energy of common materials

Generally, the more highly processed a material, the higher its embodied energy. Buildings typically use a large amount of materials with relatively low embodied energy (for example, bricks and timber) and smaller amounts of materials with high embodied energy (for example, steel).

Because most of the embodied energy of materials results from the manufacturing process, energy efficiency improvements within the manufacturing industries can make the most significant contribution to lowering the embodied energy of materials. Energy sources used to manufacture materials are also important to consider, given the large difference in environmental impact between renewable and fossil fuel-based energy sources.

Embodied energy values for some Australian materials are given in the following table, expressed as the amount of energy (in megajoules) per kilogram. However, these figures should be used with caution because:

• the actual embodied energy of a material will vary depending on where and how it is produced
• materials manufactured with recycled content will have lower embodied energy, and savings will vary depending on the proportion of recycled content and manufacturing processes used
• materials of high monetary value, such as stainless steel, are almost certain to have been recycled many times, reducing their embodied energy compared with virgin materials.

Embodied energy of common building materials*

*Note: These figures should be used with caution. See text above table. Source: Crawford, Stephan and Prideaux (2019).

For most people, it is more useful to think in terms of building components and assemblies (for example, walls, floors, roofs) rather than individual materials. The embodied energy per square metre of construction for different assembly types can then be compared. The following tables show the embodied energy values for different types of floors, walls and roofs.

Embodied energy for assembled floors

Source: Crawford (2019)

Embodied energy for assembled walls

Source: Crawford (2019)

Embodied energy for assembled roofs

Source: Crawford (2019)

Reuse and recycling

Many building materials can be reused or recycled. Savings from recycling of materials varies considerably, with savings up to 95% for aluminium, but only 20% for glass. Also, some materials may require reprocessing before they are reused which will add to the energy cost, particularly if long transport distances are involved.

Although embodied energy is an important environmental issue, the full range of environmental effects associated with building construction, use, and end-of-life, should be considered when choosing a building material. Environmental effects would include aspects such as water use, land use, raw material depletion, release of pollutants and greenhouse gas emissions, and biodiversity and habitat loss.

• Australasian EPD Programme (2018). Environmental product declarations Australasia.
• CommSec (2019). Australian houses shrink: smallest in 17 years [PDF].   
• Crawford RH (2014). Post-occupancy life cycle energy assessment of a residential building in Australia. Architectural Science Review 57(2):114–124.
• Crawford RH (2019). Embodied energy of common construction assemblies (Version 1.0). The University of Melbourne, Melbourne. 
• Crawford RH, Stephan A and Prideaux F (2019). EPiC database (Version 1.0). The University of Melbourne, Melbourne.
• ISO 14040 (2006). Environmental management: life cycle assessment – Principles and framework. International Organisation for Standardisation, Geneva.
• ISO 14067 (2018). Greenhouse gases: carbon footprint of products – Requirements and guidelines for quantification. International Organisation for Standardisation, Geneva.
• ISO 21930 (2017). Sustainability in buildings and civil engineering works: core rules for environmental product declarations of construction products and services. International Organisation for Standardisation, Geneva.
• The University of Melbourne (2019). Low energy building assembly selector. 
• Weterings T and Tustin J (2017). Energy consumption benchmarks: electricity and gas for residential customers, ACIL Allen Consulting, Melbourne, Victoria.

Learn more

• Explore the Energy section to find ways to reduce the operational energy use of your home
• Read Passive heating and Passive cooling for tips on the best materials to use in your home
• Explore Waste minimisation for more ideas on how to reduce, reuse and recycle when building or renovating

Authors

Principal author: Robert Crawford 2020

Contributing author: Murray Hall 2020