A pilot version of the UK’s first cross-industry Net Zero Carbon Buildings Standard was launched on Tuesday 24 September 2024. The UK Net Zero Carbon Buildings Standard (hereafter referred to as “the Standard”) has been created to enable our industry to robustly determine whether our built assets are net zero carbon, and in line with UK’s climate targets.
Leading organisations BBP, BRE, The Carbon Trust, CIBSE, IStructE, LETI, RIBA, RICS and UKGBC have joined forces to champion this initiative. The Standard is the first of its kind and has been developed through the combined efforts of property owners, industry experts and a number of organisations including Greengage, who have been working in the field of decarbonisation and will play a critical role in the delivery and the success of the Standard. This has allowed for a practical approach and a commitment to its delivery.
The Standard provides clear, consistent definitions and trajectories for net zero carbon aligned buildings. They are science-based and align asset-level requirements with the system-level changes needed for a net zero carbon UK. Up to this point, in the UK, net zero targets were available for a limited number of asset classes including offices, schools and homes. For all other asset classes, the industry has predominantly relied on the Carbon Risk Real Estate Monitor (CRREM) net zero trajectories to set targets, which is better suited as a stranding risk assessment tool. The Standard now covers 13 sectors (see below) and provides separate guidance for new builds and retrofits.
Who is this for?
The Standard will be relevant for anyone who wants to fund, procure, design, retrofit or specify a net zero carbon building, and for anyone who wishes to definitively demonstrate that their building is net zero carbon aligned. As a robust industry-backed initiative, the Standard should be useful to policymakers as it outlines what is needed to support the UK’s net zero carbon transition.
General principles
The Standard defines net zero carbon (NZC) as achieving balance between the greenhouse gases emitted into the atmosphere, and those removed from it. The scope of the Standard is the construction and use of buildings in the UK. It has been designed keeping in mind the sectoral budgets available to the UK to limit the increase in global average temperature to 1.5⁰C above pre-industrial levels. Some key technical principles of the Standard include:
- The Standard takes a whole life carbon approach to net zero and includes both operational and embodied carbon.
- It prioritises energy efficiency and eliminating the performance gap by using measured performance data.
- It prioritises the reuse of existing buildings and assets.
- It enhances renewable energy generation.
- It encourages demand management, so that buildings can support electrification and grid decarbonisation.
Claiming compliance with the Standard
There are two routes to claiming compliance with the Standard:
- Requirements for a ‘Net Zero Carbon Aligned Building’ claim – all requirements of the Standard must be met except for offsetting.
- Requirements for a ‘Net Zero Carbon Aligned Building (plus offsets)’ claim – all requirements of the Standard must be met.
Limits, targets and the net zero trajectory
A range of limits (maximum value) and targets (minimum value), relating to energy and carbon emission metrics are included within the Standard. The most fundamental of these are the embodied carbon and operational energy limits. Separate limits have been set for new builds and retrofits. The limit also differs for each of the building sectors.
A trajectory is provided for the sector groups, with operational energy and embodied carbon limit values for each year up to 2050. They are both expressed as intensity (kWh/m² and kgCO₂/m²). The operational energy limits within a sector remain unchanged between 2040 and 2050, acknowledging a need for properties to ideally achieve net zero carbon a decade sooner than the previously agreed 2050 mark, in order to align to the 1.5⁰C target.
Assessments will need to be carried out annually to demonstrate compliance to the relevant limits and targets. For a building to be deemed as net zero, it must also comply with additional targets and limits relating to renewable energy, refrigerants, heating delivered, and district heating and cooling networks where applicable. There is also a requirement for net zero buildings to have no fossil fuel. The Standard also sets reporting requirements around key metrics for compliance. A summary of these is provided in the diagram below.
Operational energy
Operational energy limits have been developed for 30 different building types and sub-types, with different limits for new buildings and existing/retrofit projects.
All operational energy limits are to be verified based on actual metered data in use. Most operational energy limits are based on an energy use intensity (EUI) metric in kWh/m²(GIA)/year.
For new buildings, operational energy limits will become more onerous from 2025 to 2040. The 2025 limit is representative of best practice today, with the 2040 limit being the future exemplar performance level. The EUI limit applicable for the project will depend on the year of commencement on site.
Some of the operational energy limits differ from previous guidance from initiatives such as LETI and the RIBA 2030 Climate Challenge. For new homes, the 2040 EUI limit for both sub-types (single family homes and flats) is 35kWh/m²/year in line with LETI and the RIBA 2030 Climate Challenge, however the 2025 limit is higher (45 and 40kWh/m²/year respectively). Conversely, the 2025 and 2040 EUI limits for new schools are more onerous than previous LETI and RIBA guidance.
For retrofit, the standard sets different operational energy limits depending on whether the project follows a ‘step by step’ retrofit approach or a retrofit ‘in one go’ approach. The 2040 limit is the same in both cases, however if the ‘step by step’ approach is followed, a higher EUI limit would be acceptable after first verification, with a retrofit plan to achieve the specific EUI limit by 2040. This is illustrated in the graph below from Annex A of the Standard.
Embodied carbon
The Standard has set out separate benchmarks for both retrofit and new build projects and within these, set individual targets for 15 different building types, from single family homes to science and technology buildings, up to 2050. For new build projects, the Standard currently only focuses on upfront carbon (A0-A5 excl. sequestration) and aligns with the current LETI and RIBA target parameters of excluding external works from all buildings and excluding all loose FF&E product/materials from all buildings, save for offices, culture, worship and entertainment. All calculations are expected to be aligned with the guidance set out within RICS PS 2nd edition.
Furthermore, products/materials associated with on-site electricity generation shall also be excluded from the main assessment and a comparison undertaken against the on-site electricity upfront carbon limit of 750kgCO₂e/kWp (A0-A5 excl. seq) for photovoltaics, but no limit applied to wind turbines and hydroelectrical plants. This is to facilitate an analysis to examine whether the operational carbon payback would outweigh the embodied carbon implications associated with such systems.
The benchmarks have been designed to become more stringent over time, with embodied carbon targets starting out in line with modern day best practice targets and eventually decreasing and becoming reliant on low/zero carbon technologies. For instance, a shell and core office in 2024-2025 should target 475kgCO₂e/m² (A0-A5 excl. seq), in comparison to targeting 35kgCO₂e/m² (A0-A5 excl. seq) in 2050. The scope of some unit sizes being excluded from assessment, for instance on areas of buildings occupied by a single tenant, is also set to decrease with the release of future versions of the Standard.
In comparing the targets against already existing standards, LETI proves the best control for this as they also focus on upfront carbon emissions. The majority of new build 2025 targets prove less stringent than the current LETI ‘C’ banding, save for single family homes which prove slightly more onerous. Whilst the Standard is to be a nationwide standard, in planning terms it is also worth acknowledging that the LETI ‘C’ banding currently aligns with the ‘aspirational’ threshold of the GLA targets (however these may be subject to change as they currently align with RICS v1). As such, it is deemed that the new build 2025 targets should be very achievable where a concerted effort is made on projects to achieve real carbon reductions in following the embodied carbon reduction hierarchy.
- Follows RICS PS 2nd edition;
- Currently only assessed against upfront carbon and excludes external works and any loose FF&E;
- On-site electricity generation assessed separately against an upfront carbon limit; and
- Benchmarks to become more stringent each year and capture more elements for assessment, but currently approximately aligned with LETI bandings ‘C-D’.
Refrigerants
Any systems with a total global warming potential (GWP) >3,000kgCO₂e are required to report their refrigerant leakage in any assessment. A limit has also been set on the max GWP any refrigerant installed (excl. industrial processes) should also meet at 677kgCO₂e; this falls in line with the limit of R32.
- Scope of assessment of GWP 3,000kgCO₂e; and
- GWP limit of 677kgCO₂e, in line with R32. This would not apply to existing systems that were installed before the release of the Standard.
Renewable energy
Minimum onsite renewable energy targets are applicable to both new build and retrofit projects, to encourage onsite renewable energy generation to be maximised.
The target is based on kWh/m² of building footprint/year, and varies depending on the location of the building and building type.
A lower target may apply due to site specific constraints (e.g. related to planning or lack of suitable roof area)
District heating and cooling networks
For projects that are connecting to district heating and cooling networks, there is a limit on carbon intensity of the heat/coolth delivered by the network, with slightly different limits for new and existing networks.
The carbon intensity limits for district heating/cooling will evolve as the grid decarbonises.
New networks will need to be fossil fuel free, however existing networks that currently use fossil fuels would still be allowed as long as the carbon intensity limit is met, and they have a decarbonisation plan to be fossil fuel free by 2040.
Other metrics
The following additional metrics are also covered in the Standard:
- An annual space heating delivered to the building (in kWh/m²/year) applies to new buildings in certain sectors. Space cooling delivered to the building and peak space heating/cooling energy (in W/m²) also needs to be reported.
- Operational water use needs to be reported but no limits set to comply with the Standard.
- Peak energy demand needs to be reported but no limits set to comply with the Standard.
Approach to offsetting
Carbon offsetting is optional under the Standard and compliance can be claimed with or without offsets. Where offsetting is claimed, limits must be met before offsetting can be claimed. The scope of offsetting is limited to:
- Upfront embodied carbon emissions due to new, mixed new/retrofit, retrofit works or reportable works.
- Operational energy use carbon emissions.
- Operational water use carbon emissions.
- Refrigerant leakage carbon emissions.
The Standard also sets requirements for sourcing of carbon credits and the quantity of credits that must be purchased.
What’s next?
The pilot version of the Standard provides the technical specifications, which can be adopted onto projects and into project briefs. It’s ready for the industry to start using. A pilot testing scheme is expected to be launched in early 2025, when buildings can be put forward to be used as pilot projects. There will be a selection process to enable a range of buildings from different sectors; at different stages of design, construction and occupation; and in both new build and retrofit. The feedback from the pilot testing will be incorporated into the publication of Version 1 of the Standard, expected late next year.
Version 1 will also include the methodology for the Standard to differentiate between areas or between responsibilities (e.g. for base build or for tenanted offices to assess their performance separately).
It has also been announced that once sufficient data is collected, future limits will be set for the following:
- Life cycle embodied carbon
- Space heating delivered (additional building types)
- Electricity demand management
- EUI limits (additional space types)
Can I submit a building for net zero verification now?
No not yet. Buildings will be able to be verified as meeting the Standard after the launch of Version 1 (expected late 2025). Version 1 will include details of how to verify against the Standard and provide guidelines on how it should be communicated that a building has met the Standard, including mandatory disclosure requirements.
This article has been co-authored by Amrita Dasgupta Shekhar, Rodrigo García Priego and Cameron Parker.
