Carbon footprinting: commercial property

A (carbon) step closer

18 May 2010

Roger Waterhouse continues his search for 'invisible' carbon footprints and invites commercial property managers to get involved

In my previous article (Green is the new (carbon) black, page 29, BSJ, May/June 09), I discussed the importance of establishing the carbon footprint of a construction project. This was based on the need to minimise carbon emissions wherever possible and that some leading project managers believed government controls are needed to measure these emissions over the project period (see Figure 1 - shown here as the 'Before use' stage of the full building life cycle).

Figure 1: Building life cycle stages and elements (source: A Framework for Common Metrics for Buildings, SBA 2009)

I also talked of a carbon register format, which showed the activities, emissions sources, carbon ownership and reduction potential, etc, in order to tabulate and then measure the amounts of carbon being produced during the project stage. This identified carbon sources as 'direct', 'indirect' and 'external indirect', which included embodied and associated carbon emissions (e.g. transport).

However, before the measurement of these emissions could take place, there was a need to establish an approved metric if the resulting quantities were to be accepted as an internationally agreed standard of measurement.

The environmental ratings agencies, the SBA and the UNEP-SBCI have developed a common method for measuring carbon emissions

Such an agreement was finally reached in December 2009. It began in March 2009, when an alliance of environmental ratings agencies - the BRE Trust and the US, UK and Australian Green Building Councils - signed a memorandum of understanding. This joined with the work of the Sustainable Buildings Alliance (SBA) whose members of the core group for common metrics include the BRE, CSTB in France, DGNB in Germany, FCAV in Brazil, ITC in Italy, NIST in the US and VTT in Finland. Schemes operated by these groups have previously taken varying approaches that made international comparisons difficult.

However, this work has now received important support from the United Nations' Sustainable Buildings and Climate Initiative (UNEP-SBCI), which also proposes 'a common carbon metric to support greenhouse gas emissions reductions through accurate measurement of energy efficiency in building operations'.

Together, the environmental ratings agencies, the SBA and the UNEP-SBCI have developed a common method for measuring carbon emissions. This covers:

Assessing performance at the building level (bottom up)

This measures the building's energy/water/waste consumptions from

  • building-incorporated services, e.g. space/water heating/cooling, water and sewerage, lifts, etc
  • non-incorporated services, e.g. IT, refrigerators, maintenance and repair, transport to and from the building, etc.

Assessing performance at the regional level (top down)

This considers key issues to assess the overall performance of particular types of buildings, including those at regional and national levels, which provide information needed by policymakers.

The actual measurement that has been agreed is the mass of CO2 equivalent (kg CO2-eq, i.e. the unit of greenhouse gas emissions based on impacts over a 100-year period) emitted per m2 per year, therefore:

Common Carbon Metric (CCM) = kgCO2-eq/m2/annum per building type

The next stage

We are now ready to use these agreed common metrics for the first time and work towards measuring the total emissions of a building's life cycle. This will include the important carbon footprint of the project or the Before use stage.

However, to begin the process, for reasons of accessibility (see under Embodied carbon, below) it has been decided to begin measuring the operation of building-incorporated services (within the green 'Use' stage in Figure 1), as quantities for activities within this period should be more readily obtainable. These will include:

  • energy (with sources) consumed for
    • heating/cooling/ventilation
    • lifts, escalators, etc
  • water consumption
  • waste.

More details are contained in the SBA's A Framework for Common Metrics for Buildings report, but some useful units of measurement are indicated in Figure 2.

Figure 2: A typical 'Presentation of results' table from the SBA's A Framework for Common Metrics for Buildings

Industry invite

At the January 2010 meeting of the RICS Sustainability Working Group, Martin Townsend of the BRE was invited to present a paper based on the above mentioned SBA report. This was well received and laid the foundation for an agreement between RICS and BRE to invite members to participate in a nationwide emissions survey (see panel).

The aim is to progress the measurement of carbon emissions, by establishing actual consumptions of activities associated with the building-incorporated services using existing data. This will be an important step towards establishing carbon footprint guidelines for buildings. In return, participants will receive information concerning the general analysis, although individual data will be treated confidentially where requested.


All commercial property/portfolio managers (for class A and B - retail/office/industrial) are invited to participate in this nationwide survey and contribute as soon as possible so that the use of the CCM can be further tested to measure emissions from the operation of buildings over a 12-month period.

For more information, contact Martin Townsend, Director of BREEAM, BRE Global, T +44 (0)1923 664676

Embodied carbon

It is hoped the results from the operational/'Use' period will provide empirical evidence of realistic performance and hence of potential carbon emissions (as far as can realistically be measured at present).

However, to establish the full life cycle footprint or trace the footprints for each of the three stages (especially the project/Before use stage) it will be necessary to establish a metric for embodied carbon. This includes the full manufacturing process (commencing with the mining of any raw materials) and all transportation associated with the supply and distribution process throughout manufacture to end product.

Although calculations for these emissions have been undertaken for a limited number of products, an international metric for embodied carbon still has to be agreed. Nevertheless, some organisations claim to have already established their own (e.g. Davis Langdon, The Road to Green Property). However, it is important for a systematic analysis to be established internationally to ensure consistency across calculations and talks are ongoing by the above referred parties to achieve this.

Once agreement for this metric has been achieved, it should open the way for assessments or values to be agreed for key elements (e.g. reinforced concrete, steel, cement, timber, plastics, clayware, etc) up to more complex components and systems (e.g. cladding, glazing, heating and ventilation).

This should then allow emissions comparisons of structural and M&E systems, components and cladding, and roofing systems to be made so that clients' project managers and designers can evaluate the total carbon footprint created by each option. It is probable that guidelines will be established by governments, possibly by building volumes or areas that (together with costings) will shape the future of not only the appearance of our buildings but of life cycles, materials/raw material sources and their travel distances from projects, etc.

Although calculations for these emissions have been undertaken for a limited number of products, an international metric for embodied carbon still has to be agreed

Similarly, energy is likely to be evaluated not just by kWh (see Figure 2) but by proportion of 'renewability' contained within that metric. Equally, there could be guidelines or controls over water and waste consumptions during all three phases of the project life cycle contained in Figure 1.

However, it would be a mistake to assume that the road ahead was straightforward when it comes to comparing the CO2 emitted during the manufacture and delivery of two similar products from two countries. Many of the material and product supply chains are complex and contain huge uncertainties. Multiple variables will need to be established and agreed upon before a realistic system of comparisons can be made.

For example, in terms of transportation emissions, how do we compare a product shipped from Africa with a similar one transported by road or rail from Europe or central Asia? And how do we measure the waste consumed and the difference between machines driven by oil or coal?

Carbon footprints of buildings may be invisible, but unless they are considered when designing for sustainability, then preventing the collapse of our ecosystem could be seriously impeded. Achieving international agreement is therefore vital. The Common Carbon Metric now has to be tested and this can continue while progress is made towards an international agreement for the Embodied Carbon Metric. For the time being, however, we are at least, a (carbon) step closer.

Roger Waterhouse is Vice Chair of the Project Management Professional Group, a member of the RICS Sustainability Working Group and a Consultant in Project Management with the College of Estate Management

Further information

Related competencies include: M009, T003, T013, T021 and T022