At present, in the UK, there is no single agreed definition of what constitutes a net zero building. In recent years, developers, clients and project teams have committed to delivering, or operating, net zero carbon buildings. But claims of net zero can be based on any one of a plethora of different guidelines and standards, all with different scopes and targets.
Initiatives include the Riba 2030 Challenge, the UK Green Building Council (UKGBC) framework, the NABERS UK star ratings and the Low Energy Transformation Initiative (LETI) – in addition to the CRREM Global Decarbonisation Pathways and Science-Based Targets for existing buildings.
In 2022, a cross-industry group, involving major organisations such as BBP, BRE, the Carbon Trust, CIBSE, IStructE, LETI, RIBA, RICS, and UKGBC, launched a project to develop a definitive, industry-recognised net zero carbon buildings standard (NZCBS). This highly collaborative effort has been guided by the aim of unifying the existing initiatives, while providing clarity, consensus, consistency and credibility as to what defines a ‘net zero’ building. A beta (test) version of the standard is due to be published this spring.
Net Zero Carbon Buildings Standard: Key details
The NZCBS will be a voluntary standard that provides a clear definition of net zero and robust targets for new building projects, existing buildings and retrofits. It will be a single reference point for any developer wishing to demonstrate that their development or building has achieved net zero carbon.
As a start point, a net zero building is defined by one whose operational and embodied carbon performance is within limits which allow the UK built environment to stay within its own allocation of remaining carbon budget, in order to limit global warming to 1.5°C this century.
To assess this, the key metrics specified in the standard include an operational energy demand (kWh/m2/year) target (the energy needed to run buildings) and an embodied carbon (kgCO2e/m2) target (the sum of the energy used to create the building).
The standard will set out building performance criteria, but not advocate specific design approaches such as Passivhaus. It will be overseen, and managed, by a Technical Steering Group and Governance Board formed from the cross-industry group responsible for developing the standard.
Accelerating the UK’s built environment net zero journey
The hope is that the NZCBS will help to accelerate industry progress towards decarbonisation and ensure alignment with the UK’s wider climate goals. It comes at a time when the sector is under scrutiny, from its own institutions, about the need to increase the pace of decarbonisation.
In late 2023, in the first update to its Net Zero Whole Life Carbon Roadmap report, the UKGBC said that the built environment must decarbonise nearly twice as fast to meet agreed industry carbon reduction targets for 2025.
2023 also saw the RICS launch the second edition of its Whole Life Carbon Assessment for the Built Environment (WLCA) standard, reflecting an increased focus on embodied as well as operational carbon. Importantly, the updated, global standard provides a more developed understanding of the carbon costs and benefits of design choices in construction and infrastructure projects and assets. The new NZCBS incorporates the RICS WLCA standard’s methodology to assess upfront, embodied, operational, user and whole-life carbon.
The NZCBS is the most thorough attempt to date by industry to set science-based net zero carbon limits and targets for UK buildings; other sector specific net zero building standards do exist (see box below ‘Setting a precedent’).
While it is a voluntary standard, there is potential for the NZCBS to be used to support policymakers in setting robust requirements that deliver buildings aligned with a 1.5°C decarbonisation pathway for the UK. The standard’s targets will necessarily be challenging, requiring a shift away from traditional practices in the construction and operation of new and existing buildings. But the looming climate crisis demands nothing less than a complete reset of priorities in our approach to how we construct and run our buildings.
Box: Setting a precedent: Net Zero Building Standards in the UK
The new net zero carbon buildings standard (NZCBS) will be the UK’s first cross-industry standard for all major building types, based on a 1.5°C trajectory. However, there are sector specific standards that share the same overarching goal:
- The NHS Net Zero Building Standard provides technical guidance to support the development of sustainable, resilient, and energy efficient buildings that meet the needs of patients now and in the future. The Standard applies to all investments in new buildings and upgrades to existing facilities that are subject to HM Treasury business case approval process and are at pre-strategic outline business case approval stage from 1 October 2023 onwards.
- The Net Zero Public Sector Buildings Standard is a voluntary standard, owned by the Scottish Government and applicable to public sector new build and major refurbishment projects.
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