The Net Zero Carbon Buildings Standard and the proposed Part Z

1 Similarities and differences in brief
2 The Net Zero Carbon Buildings Standard (NZCBS)
3 Proposed UK building regulations Part Z
4 Related articles on Designing Buildings
5 External links

[edit] Similarities and differences in brief

The Net Zero Carbon Buildings Standard (NZCBS) and the proposed amendments to the Building Regulations 2010 known as Part Z are two initiatives that have been developed over a similar timeframe with some of the organisers being involved in both initiatives. Both NZCBS and Part Z look towards reporting of whole-life carbon emissions (embodied and operational), anchored in the RICS Whole Life Carbon Assessment methodology, setting limits for upfront embodied carbon (modules A1–A5). NZCBS applies strict science-based caps whilst Part Z proposes regulatory limits, initially more lenient but intended to ramp up over time and both reference guidance from established institutions such as RICS, RIBA, CIBSE, IStructE, LETI, and UKGBC.

Crucially the difference between NZCBS and Part Z is that one is a voluntary standard that has already been launched with pilots being carried out, the latter aims to introduce a standard as a mandatory requirement of the Building Regulations from 2026-2028. The NZCBS would be applicable to all buildings types and cover relatively ambitious targets for all major sources of carbon within the built environment to evidence net zero with the definition aligned with scientific carbon budgets and 1.5 °C trajectory. Part Z has a clear focus on introducing a requirement to the building regulations that covers embodied carbon, which is currently not included in the regulations, thus becoming a mandatory requirement, similar to the assessments of operational energy that are currently required.

For more information see the sections below or follow these links https://www.nzcbuildings.co.uk/ and https://part-z.uk/

[edit] The Net Zero Carbon Buildings Standard (NZCBS)

The Net Zero Carbon Buildings Standard (NZCBS) was first discussed in 2022, with a cross-industry partnership of leading organisations announcing they were joining forces to develop the UK’s first standard for identifying and verifying buildings as net zero carbon. A long-awaited clear standard needed by the industry, the ‘NZCBS’ aimed to set out a single, agreed set of performance targets for different asset types, to enable buildings claiming net zero carbon to demonstrate that they meet science-based decarbonisation trajectories. In November 2022 a call all for evidence was launched.

Consultations were carried out through 2023 with the voluntary framework led by BBP, BRE, CIBSE, Carbon Trust, IStructE, LETI, RIBA, RICS an UKGBC. The asset-level standard was designed to incorporate and address all major sources of carbon within the built environment. These include embodied carbon from materials and construction processes, operational energy use, and the integration of renewable electricity generation. The limits and thresholds set being derived from the UK construction sector’s allocation of the remaining national carbon budget, ensuring that the requirements are firmly science-based and reflect the urgency of climate goals.

The Standard recognises the diversity of the UK building stock, and as such will set tailored requirements for different asset types, whether they are new-build, existing, or retrofit projects, covering all major sectors that make up the majority of buildings in the UK, such as housing, offices, hotels, sports and leisure facilities, and more. To be classified as a “Net Zero Carbon Aligned Building” under this voluntary framework, an asset must comply with all the mandatory limits and criteria that are outlined in the standard. The classification providing a trusted benchmark, to ensure that claims of net zero carbon within the construction and property industries are robust, consistent, and in line with international climate commitments.

After some time developing the standard and its supporting documents, the NZCBS pilot version was launched in September 2024, a single, consistent definition of what “net zero carbon” means for buildings, to ensure the definition is scientifically aligned with the 1.5°C trajectory set out in the Paris Agreement. To be classified as an "Aligned Building” under the framework, an asset must comply with all the mandatory limits and criteria outlined in the standard. As such the classification intends to provide a trusted benchmark, ensuring that claims of net zero carbon within the construction and property industries are robust, consistent, and in line with international climate commitments.

The standard includes free guidance documents and a detailed proforma excel spread sheet which can be access here. At the time of the launch Katie Clemence-Jackson, Chair of the Standard’s Technical Steering Group, said:

“The Standard has been created not just using industry data on what is achievable, but also cross referencing this with ‘top down’ modelling of what is needed to decarbonise our industry in line with 1.5°C aligned carbon and energy budgets. It covers all the major building sectors, as well as both new and existing buildings.With access to the Standard, the built environment industry is equipped to target, design and operate buildings to be net zero carbon aligned, driving the positive change that we need to meet our climate goals. I would like to thank all our volunteers from across the built environment who have contributed their time, experience and knowledge to allow us to develop a robust Standard. This has been an immensely collaborative process, and we couldn’t have achieved it without your support.”

David Partridge, Chair of the Standard’s Governance Board, said: “The Standard brings together data from thousands of buildings submitted by professionals from across the built environment and will be an important step towards a net zero carbon economy. I encourage everyone within the built environment and real estate sector, from investors, funds and lenders, through developers to building designers, managers and contractors, to start to use the pilot version of the Standard. We will shortly be launching a pilot testing programme to glean feedback on applying the process on real projects.”

[edit] Proposed UK building regulations Part Z

In July 2021, the construction industry proposed Part Z, an amendment to the UK building regulations to regulate embodied carbon on all major construction projects. The amendment, if introduced (currently only an industry proposal, and not backed by government), would require whole life carbon assessments and compliance with embodied carbon limits for projects greater than 1000m2 (or 10 dwellings). The proposal was publicly launched in Westminster in March 2022 as one which would require developers to assess and report on the emissions embodied in the construction of a new building, and would allow for limits to be set on those embodied emissions, which could be ratcheted down over time, as low-carbon materials and processes improve.

The proposal was written by 5 construction industry professionals: Will Arnold (Head of Climate Action at the Institution of Structural Engineers), Tim den Dekker (Associate Architect at Feilden Clegg Bradley Studios), Dr Jannik Giesekam (Research Fellow at the University of Strathclyde), Dr Julie Godefroy (Head of Sustainability, Chartered Institution of Building Services Engineers and London Energy Transformation Initiative) and Simon Sturgis (Architect, Carbon Consultant, Royal Institute of British Architects & Royal Institution of Chartered Surveyors).

The principle of introducing embodied carbon regulations is supported by over 150 leading organisations involved in the UK building industry (statements available at https://part-z.uk/industry-support). These include The Institution of Civil Engineers (ICE), The Chartered Institution of Building Services Engineers (CIBSE), Chartered Institute Of Building (CIOB), The Institution of Structural Engineers (IStructE), The Royal Institute of British Architects (RIBA), The Royal Town Planning Institute (RTPI), The Chartered Institute of Architectural Technologists (CIAT), The Steel Construction Institute (SCI), The Structural Timber Association (STA), UK Green Building Council(UKGBC), Off-Site Homes Alliance (OSHA), Construction Industry Council (CIC), along with many others and numerous leading firms.

In July 2025 President of the Chartered Institute of Architectural Technologists (CIAT) Eddie Weir PCIAT, said:

"I’m delighted that CIAT has joined the many other industry bodies already supporting the campaign for 'Part Z'. Architectural Technology is all about creating buildings that perform to the highest standards, meeting the needs of people and planet. Building Regulations set requirements for the in-use performance of buildings, but 'embodied' emissions make up an increasingly large share of the climate impact of a building over its lifetime. This is a huge gap, and closing it is essential to achieving the emissions reductions we need to see in the built environment sector over the coming 25 years."

"Chartered Architectural Technologists work tirelessly with clients and professional colleagues across the sector to deliver the best performing, most sustainable buildings possible. Until 'Part Z' is established as a regulatory requirement, I encourage our members and affiliates to do all they can to minimise embodied carbon in the buildings they design."

Chis Halligan MCIAT, Chair of the CIAT Climate Society, said:

"The decisions we make over the next few years will have a profound impact on our climate, our communities and our wellbeing for decades, perhaps centuries, to come. We know we need to reduce the emissions associated with construction; if cement were a country, its carbon emissions would be third only to the USA and China."

"But to deliver the best outcomes we need to go further, embedding sustainability as a design objective from the outset, rather than treating it as a bolt-on or optional extra. That way, we can deliver buildings which stand the test of time, tread lightly upon the planet, and deliver safety and resilience for building users and wider communities."

"'Part Z' only addresses embodied carbon, but by forcing designers and developers to consider sustainability from the outset, it can help raise ambitions across the sector, driving lasting change and preventing a race to the bottom. That means it’s a great place to start."

Caroline Gumble, Chief Executive Officer at CIOB, said on the proposal: “Sustainability and the push to achieve net zero have, quite rightly, taken their place as priorities in construction.

“CIOB is supportive of regulatory moves which enable a focus on embodied carbon, not just operational carbon emissions, and add weight to its consideration as part of the construction and development process. Sustainability is already something which informs much of our work - and will for years to come - and we have been clear to our members that opportunities to take a more environment-centred approach, combined with practical measures and clarity in legislative requirements, should be welcomed. The industry needs to walk the walk on minimising climate change, not just talk the talk, and we expect CIOB members to update their knowledge through CPD and understand how they can make a meaningful positive contribution to achieving net zero.”