Why we need to focus on embedded energy in buildings

No building or development project can be deemed to be environmentally sustainable without an assessment of its life cycle environmental performance. This so often fails to be done, or even thought about. But this is changing. A new report lists resources to help developers, quantity surveyors and planners take this forward.

A crucial aspect of life cycle performance is energy use, i.e. the embodied energy. Embodied energy refers to the energy used in the manufacturing of the materials used in the project, in transportation to the site, construction, maintenance and the removal and disposal or recycling of materials and restoration of the site at the end of its life.

If this is added to operational energy, i.e. the energy used by the occupants of the building or development, then we can really have a much better idea of whether or not a project is ‘zero or low energy’, or even ‘negative energy’, (which could happen if the structure locked up atmospheric carbon in its materials (for example timber, timber products, straw, etc.).

A new white paper produced by CBx represents an attempt to scope existing resources, datasets and legislation for calculating embodied energy. It includes work by the UK Green Building Council, which has identified 15 challenges to keeping embodied energy low. Of these the top four are:

1. Consistency in method
2. Availability of comparable data
3. Industry attitude
4. Worries about the extra cost and complexity.

Embodied carbon example for a new air-conditioned office. Source: Embodied Carbon Industry Task Force Recommendations – June 2014

The context

As building regulations force improvements in the operational energy efficiency of buildings, the embodied energy of those buildings becomes significantly more important and has also in practice been seen to be actually increasing.

The report notes:

“In many cases designers will employ a high-tech approach in order to minimise operational consumption, using highly processed materials, complex plant equipment and a sophisticated, automated control system. In terms of whole life performance, this tends to shift the carbon cost from operational consumption to the end body carbon of the building fabric.”

Standardisation of the industry reporting of embodied energy is urgently needed.

The report also notes that the Royal Institute of Chartered Surveyors (RICS) has produced guidance on a method for the calculation of embodied carbon from cradle to end of life across four main sectors, with case studies.

These illustrate that, over a 30 year period, around 50% of the total carbon is tied up in embodied (vs. operational) activities, which includes the embodied carbon of the initial materials, emissions during construction and the maintenance & repair cycle.

Furthermore, the embodied vs. operational split differs from sector to sector:

• Embodied carbon is greater in buildings housing low energy-intensive activities such as warehouses.
• In supermarkets it is roughly 50%.
• In offices it accounts for over half the whole life carbon cost.
• In a semi-detached house it is much higher than 50%.

Graphs of average embodied carbon in different types of development or building. Source: RICS.

In the UK the property industry is lagging behind industries such as highways, rail and the water industry in reducing embodied energy. This is because the relevant bodies include embodied carbon calculations in their design, refurbishment and maintenance proposals and because there has been work on to calculate the carbon factors for components such as pumps.

Proportion of total UK CO2 emissions that construction can influence (split into in-use emissions for residential and non-residential buildings and construction-related emissions) Source: Department for Business Innovation and Skills.

Resources

A number of metrics, tools and data sources exist:

• There is a British Standard 15978 which sets out a framework for the analysis of embodied carbon. This is the standard upon which all life-cycle cost analysis is based [paid BS link here];
• The RICS method is applicable all over the world and simplifies Life-cycle Cost Analysis for quantity surveyors;
• An embodied carbon calculator provided by the Environment Agency [this is an XLS spreadsheet];
• Architype released their bespoke calculator RAPIERE;
• The ICE database [Inventory of Carbon and Energy although this is now seven years out of date];
• The Franklin Andrews System and Black Books;
• The Chartered Institute of Building Services Engineers have produced TM56 which aims to help engineers and consultants to understand the principles of resource efficiency.

Data sources in the future will come from Environmental Product Declarations (EPD). These are verified documents that report environmental data of products based on life cycle assessment (LCA) and other relevant information.

The US has hundreds of these already registered, while Germany has close to 1000. The UK lags behind with only seven.

Building Information Models (BIM) (proprietary software) sometimes have embodied carbon capabilities, thus facilitating more accurate and less time consuming calculations.

Life cycle assessment is already standardised through a range of ISO documents, including ISO 14040:2006 and ISO 14044:2006, which cover principles, framework requirements and guidelines and, published six years later, ISO/TR 14047:2012 and 14049:2012, which help with applying the earlier standards the impact assessment and inventory analysis.

Legislative and other requirements

Legislative requirements for reporting embodied carbon are few and far between. In the UK there is no requirement in Part L (Conservation of fuel and power) Building Regulations. In the eco-building accreditation system BREEAM there are one or two credits available per project.

The Green Guide to building materials is tangentially linked to embodied carbon including the requirement as a proportion of an A-rating.

Brighton, the UK’s first declared ‘one planet’ city requires an embodied carbon plan from developers in planning applications. [See linked article below for more.]

Examples:

London 2012 Olympic Stadium

Achieved a 38% reduction in embodied carbon through:

• 100% recycled aggregates;
• Cement substitutes;
• Reuse of ‘waste’ steel from a local gas pipeline.