Why is embodied energy important?

One of the main focuses in the construction industry in recent years has been the desire to create energy efficient buildings. The next step in the push for "greener building" is embodied energy, which the current definition of a zero carbon building does not account for. The publication of the Emerging Findings report in Spring of this year by the UK Government's Innovation and Growth Team contains recommendations to reduce carbon emissions by measuring and accounting for embodied energy. The report also suggests this strategy to tackle embodied energy should be incorporated into the Treasury's Green Book for public sector procurement. It would seem that regulation of embodied energy is inevitable, and is likely to be a finding in the final report of the Innovation and Growth Team due to be published later this year.

What is embodied energy?

Embodied energy is the total energy consumed in the extraction, manufacture and transportation of the materials (such as cement, steel, wood) used in a building. While the previous focus has been on the operational energy used by a building, taking into account the embodied energy of a building will give the full carbon footprint of a building - often called a "cradle to grave" analysis.

The amount of embodied energy in a building will have a strong relationship with the building type and use: the Royal Institute of Chartered Surveyors' tool for calculating embodied energy suggested that embodied energy contributed to:

  • 60% of the lifetime carbon footprint of a warehouse (as this type of building consumes a small amount of operational energy);
  • compared with 30% of the carbon footprint of a dwellinghouse; and
  • 20% of a supermarket's footprint.

The key factor is the carbon impact of a material over its lifetime - the RICS tool allocates a particular lifespan to different building elements, to take account of the fact that while some materials may last hundreds of years, a central plant, for example, may only last 20 years. The University of Bath's Sustainable Energy Research Team has been working on a database that details the embodied energy and carbon of a large number of building materials. Other tools are in the process of being developed, but at present we still require robust, objective criteria to determine the amount of embodied energy related to a building, that can be universally applied. In the future it is hoped that software will be created that allows users to adjust various elements of their planned building in order to reduce its "cradle to grave" carbon footprint.

Practical and legal implications?

What practical steps can be taken to reduce the embodied energy footprint of a building, and what effect may such steps have on construction contracts? One method of limiting embodied energy is to re-use materials from buildings that are being demolished, rather than manufacturing new construction materials. However, developers will need contractual comfort from the contractor/professional team that the re-used materials are suitable for use for the relevant construction element of the building. This may be problematic, however, as it is unlikely that a contractor will assume the same responsibility for re-used materials as it would do for new materials: in the latter case, a contractor will have recourse to the supplier of the materials should they prove to be unsuitable. Similarly, consultants are only likely to sign off on re-used materials to a limited extent. Developers may therefore find they have less legal recourse against their contractor and professional team in relation to buildings that incorporate re-used materials. This may potentially affect the marketability of buildings from the point of view of funders, or institutional purchasers.

Clearly, if a developer wishes to address the question of embodied energy in the procurement of a building, it is critical that the developer's requirements are notified as early as possible to the design team and the contractor. Incorporating embodied energy obligations in building contracts and professional appointments is a useful way of ensuring that the team is focused on this objective, and often provokes debate as to whether, or how, such an objective can be achieved.

This still leaves open the question of what the contractual consequences of a failure to achieve a certain embodied energy target would be. This question will probably remain unanswered in the short term until suitable tools and objective criteria for assessing the embodied energy of a building are developed. Such tools will provide assistance in quantifying the impact on the value or marketability of a building if an embodied energy target is not met, and will therefore result in the corresponding contractual obligations becoming more meaningful.

Locally sourced materials

Materials sourced locally have a lower transportation footprint than those sourced from further afield, and would seem therefore to be a reasonable approach to take, when trying to reduce embedded energy levels. However, a requirement to use locally sourced materials will also give rise to legal questions in both the public and private sector: an obligation to use a local supplier might lead to a potential conflict with the EU procurement regulations; while a similar requirement in the private sector may be interpreted as requiring "nominated suppliers", or may interfere with a contractor's established supply chain. Many UK developers and retailers have a recognised supply chain which they use on their projects. If most of these are based in, for example, the south east of England, this may need to be considered if a new development is being constructed in the north of Scotland.

Environmental targets

It is now common for construction contracts to take into account a developer's requirement to achieve particular environmental targets such as BREEAM ratings. The latest revision of the JCT/SBCC standard form building contracts provide for an opt-in sustainable development and environmental considerations provision which requires the contractor to suggest economically viable amendments to the Works, that may result in an improvement in environmental performance of the carrying out of the Works or the completed Works. Should objective criteria to measure embodied energy be accepted in the construction industry, it is hard to envisage how the embodied energy in construction materials would not be caught by an environmental provision such as the one in these standard form contracts.

To read the Innovation and Growth Team's Emerging Findings Report click here.