Net Zero Carbon Verification

Hero Bennett

Sustainability Leader

Max Fordham LLP

The last year has seen an array of projects and buildings claiming to be net zero carbon, however looking beneath the surface there is not always a solid foundation to these claims. Just as a business would seek to have a third-party audit to verify carbon targets, third-party verification is a necessary step to present a credible case for claiming net zero carbon status.

UKGBC Net Zero Carbon Buildings: A Framework Definition

The currently accepted standard in the UK is the UK Green Building Council Net Zero Carbon Framework Definition. It is well-defined for offices where minimum standards of operational energy have been published – these need to be met in practice to verify your building as net zero carbon in operation. For other building types, there is much less clarity and levels of efficiency that need to be met are subjective.

The new UK Net Zero Carbon Building Standard is expected at the end of 2023. A cross-industry collaboration that will replace the UK Green Building Council’s Framework definition with levels of construction and operational carbon defined for different building types for both new buildings and refurbishments.

The main principles are expected to follow those of the UK Green Building Standard and therefore following these while also considering the consultation information of the new UK Building Standard is the best way to design for the emerging standard.

The UK Green Building Council’s (UKGBC) net zero carbon framework currently requires public disclosure through a readily accessible location, in most cases an annual sustainability report or organisation’s website. A third-party audit is also required to provide transparency on the sources and processes used to determine the net zero carbon balance.

Third Party Audit

The third-party audit should come from an independent professional organisation that is familiar with reporting and the framework. It is anticipated that in the future a more robust audit route will be introduced, in all likelihood this will align with either existing or emerging reporting or certification methodologies.

For offices, the consultation version of the UK Net Zero Carbon Building Standard reinforces the alignment with the NABERS standard. NABERS UK Design for Performance is a process that enables developers and owners to achieve a rating for the energy efficiency of new office buildings based on the in-use energy data. For example, if an office building can demonstrate being designed or measured in-use as achieving a NABERS 5.5* rating it can claim net zero carbon levels of efficiency.


In terms of operational carbon, the UKGBC’s NZC framework is not a design standard but an operational one requiring annual verification based on metered energy consumption (Scope 1 and 2 building emissions only) and applies equally to new builds and existing buildings. Energy consumption can vary in buildings from year to year, as tenants and systems come and go. The robustness of the UKGBC standard is underpinned by the requirement for annual verification.

For a new build the verification report could be combined with an aftercare appointment where an appointed professional has the responsibility for reviewing energy meters regularly throughout the year and helping to optimise the building to reduce emissions. At the end of year one of operation there will be a year’s worth of energy data and the verification report can be written. It may well be the case that the required level of operational energy efficiency is not met after one year and so many clients are implementing aftercare processes for two or three years post-completion.

Additionally, for new builds operational carbon status can only be claimed when Net Zero Construction is met. Minimum reporting of the embodied carbon of the building is required in line with the RICS Professional Statement ‘Whole life carbon assessment for the built environment’ at RIBA Stage 6 (Handover). This is important as it requires working with the contractor to understand which materials actually went into the building, rather than using a theoretical design stage assessment. This should ideally be carried out by the original embodied carbon consultant who has access to the design stage models but could also be a contractor requirement to undertake a new embodied carbon assessment. There are emerging technologies helping contractors to track the embodied carbon of products brought to site.

All reporting should also demonstrate carbon offsets purchased to achieve the net zero carbon balance and their alignment with the UKGBC’s requirements.

Global Net Zero Carbon Projects

Some countries have their own net zero carbon standards to comply with the World Green Building Council’s Advancing Net Zero programme, often linked to local certification schemes. The Institute of Living Futures claims to have produced the first international net zero carbon standard. Like the UKGBC framework it requires offsetting embodied carbon as well as basing energy consumption on metered operational energy one-year post occupancy. As it is focused on new builds, reporting is only based on year one performance. Verification is carried out by the institute itself for a fee based on the size of the building.

Honesty and Transparency

There is a significant amount of greenwash which can be applied under the heading of net zero carbon, however the approach of measuring, reporting and auditing the impacts of our existing and new buildings set out by the UKGBC encourages honest reflection and public review. Shining light on our buildings’ energy consumption and carbon footprints will undoubtedly lead to better understanding of our buildings’ climate impacts and the need to take effective steps to reduce these impacts and to become net zero carbon.