New rules aim to standardise carbon accounting

In March 2023, climate consultancy Net Zero Now was awarded an Innovate UK grant to develop a new, industry-standard approach for carbon accountants and assessors.

The project aims to allocate emissions factors to products and materials used in construction where no credible environmental product declaration (EPD) is available for them.

Overseen by a steering committee that includes the UK government, RICS, the UK Net Zero Carbon Building Standard, CO2nstructZero, the UK Green Building Council and more, Net Zero Now's proposal is based on a set of rules that will standardise the selection of activity data and emissions factors.

Initiatives such as RICS' own Whole life carbon assessment for the built environment professional standard (WLCA) and the forthcoming UK net zero carbon buildings standard are critical to ensuring that the industry's carbon is measured in a clear and consistent manner.

To quantify the embodied carbon of a building, carbon accountants need to know the inputs – the volume of resources consumed during the build process and any subsequent repair, maintenance and improvement work – as well as the emissions factor of a single unit of those resources.

This factor represents the carbon dioxide or equivalent emissions associated with a tonne of concrete, a building element, a kilowatt–hour of electricity used and so on.

A lack of consistency in the inputs for carbon accounting will therefore mean a lack of consistency in the output, which is not only a barrier to climate action itself but also undermines the credibility of initiatives such as WLCA.

However, a universal dataset for all products and materials does not currently exist, and this leads to discrepancies in reporting.

To address this issue, carbon accountants currently use one of two approaches, or a combination of the two.

The first is a spend-based approach, which assigns emissions based on the financial expenditure on a given service.

This provides consistency but not accuracy, because it assumes an average level of emissions for any specific service and therefore offers no process or incentive for contractors to minimise actual emissions.

For instance, if assessors use an average number for emissions from plumbing based on the amount spent, it would make no difference if the actual emissions were high or low.

As a result, there is no reason for a plumber to invest in reducing their emissions as this would not be recognised or rewarded.

The second approach by contrast uses EPDs to offer accuracy, provided these themselves are calculated correctly. But given that few products have such declarations, there is little consistency in the way emissions factors are being assigned.

Although it is possible to combine these methods, the shortcomings of both in general and the use of averages in particular meant that a new approach was needed.

This should lend consistency to imperfect data, and enable the following:

• more granular and focused measurement of embodied carbon emissions from construction projects, in accordance with WLCA and relevant government regulations
• more accurate measurement of annual carbon emissions from small construction companies, in accordance with the GHG Protocol and relevant regulations.

Using these rules, construction companies will be able to provide carbon quotes based on existing designs, bills of quantities and so on – thereby allowing customers to identify and reward low-emissions contractors – as well as carbon reports based on as-built work.

Technology companies will likewise be empowered to develop carbon accounting software that makes it simple and affordable for construction firms to take credible climate action with legitimacy and transparency.

The latest draft of these rules has been reviewed by the project steering committee and a wide range of other industry stakeholders, with the intention that the final version will be included in RICS training material on WLCA.

In the meantime, professionals are invited to review the rules and offer feedback. Your input is key to ensuring these rules are effective – and empowering the industry to measure and manage its emissions.