Industry-led UK Net Zero Carbon Buildings Standard pilot launched
The UK Net Zero Carbon Buildings Standard Guide: Part 1: Key principles and overview
Contributor
Hareth Pochee
MPhys
Principal Engineer
The pilot version of the UK Net Zero Carbon Buildings Standard (the Standard) was published in September 2024. The full document can be downloaded here.
The Standard has been produced by a range of industry professional organisations including RIBA (architecture), IStructE (structural engineering), CIBSE (services engineers) and RICS (surveyors), along with a large team of other industry organisations and professionals.
It aims to set out unambiguously, for a wide range of scenarios, the characteristics that buildings and building projects need to be aligned with the UK’s strategy to become net zero carbon by 2050. The Standard builds upon and supersedes previously published approaches such as the UKGBC Net Zero Carbon Building Framework, the RIBA Climate Challenge and the various LETI design guides.
Read more from our guide:
Part 1: Key principles and overview
Part 2: Embodied carbon
Part 3: Operational energy
Part 4: On-Site renewable generation
Part 5: Operational Water Use
Part 6: Fossil fuel free
Part 7: Electricity demand management
Part 8: District heating and cooling networks
Part 9: Space heating and cooling
Part 10: Refrigerants
Part 11: Carbon offsetting
1. Key principles and overview
Net zero aligned, offsetting is optional
The preceding UKGBC NZC Building Framework didn’t specify many limits for operational energy or embodied carbon but required projects to achieve net zero (carbon emissions) by purchasing carbon offsetting.
The new UK NZC Buildings Standard approach is different; it includes mandatory limits for a range of buildings’ characteristics such as operational energy consumption and upfront embodied carbon but offsetting is not required, it is optional. Hence the terms Net Zero Carbon Aligned and Net Zero Carbon Aligned Plus Offsets are defined as the correct ways to describe the intended outcomes.
Plugging holes
The Standard has made great progress addressing a range of known problems with previous schemes such as the range of building types, different targets for new build and retrofit, how to deal with projects on district heating systems, addressing refrigerant gas global warming potential etc.
Types of buildings
Previously published guidance (such as UKGBC Framework) covered a small range of building types, such as homes, schools, offices and NHS buildings. The new Standard provides requirements for approximately 30 building types, including commercial, culture and entertainment, data centres, healthcare, higher education, homes, offices, retail, schools, sports and leisure and storage and distribution.
For projects with mixtures of types, the Standard takes a floor area-weighted average approach.
Types of build projects (works types)
The Standard provides requirements for a range of different project types including:
- New Build
- Retrofit in One Go
- Retrofit Step by Step
- Office fit-out scenarios
The Standard sets out how to classify projects as one or more of the above works types depending on the extent of different types. Different works types have different performance requirements such as operational energy and embodied carbon limits.
Characteristics considered
|
Characteristic |
Selected requirements (not a comprehensive list) |
|
Fossil fuel free |
· In general, buildings to not use fossil fuels during their operation · Some exceptions, for example back up power for life-safety type systems |
|
Embodied carbon |
· Limits for Upfront Embodied Carbon (A1-A5) based on as-built model · Different limits for different building types and works types · Methods for office shell and core and fit out type projects · Range of exclusions such as external works and renewable energy systems |
|
Operational energy |
· Limits for the annual building energy consumption based on as-measured building in use data · Different limits for different building types and works types · Retrofit limits are less stringent than New Build ones · kWh/m²/yr is the basis in most cases · New build values thought to be around 60% to 80% less than typical existing building stock · The limits are tied to the year of construction or retrofit. A project keeps its initial limit value for subsequent years of NZC assessment. |
|
Renewable electricity generation |
· Requirements for the amount of on-site renewable electricity generation based on as-measured in use data · 30 to 75 kWh/m² building footprint / year depending on location and building type · A range of dispensations for issues such as site constraints and network capacity |
|
District heating or cooling networks |
· Limits on the carbon intensity of heating and cooling networks · Different limits for existing or new networks · For heating the limits are based on the carbon intensity of a heat pump with SCOP of 2.8 and some network losses |
|
Space heating and cooling |
· Limits of 15 to 20 kWh/m²/yr heating delivered to the building (depending on building type) · Limits for delivered cooling and peak heat demand (W/m²) proposed for future versions |
|
Refrigerant gases |
· Limits on the GWP of refrigerant gases used · 677 kgCO2e/kg, which corresponds to that of R32 |
Text
Approach and verification
As far as possible, the Standard is based on actual, as measured data (rather than theoretical models). For example, as measured operational energy consumption over a 12 month period. An exception is embodied carbon, which cannot be directly measured, only calculated in theory because (most of) the emissions occur remotely, from factories.
Similar to the UKGBC Framework, the Standard will require building projects to undergo third party audits to verify that the relevant standards have been met. The specific requirements have not yet been published but are anticipated to be so in the not-too-distant future.
It’s anticipated that the process will require projects to gather the relevant evidence and submit a report to a third party verifier who will then review the information to determine if the requirements of the Standard have been met, allowing a project to claim 'net zero carbon aligned'. For example, this will include as measured meter readings, demonstration of the building use types and floor areas, embodied carbon model reports, district heating carbon intensity data, etc.
Differing from the previous UKGBC approach it appears the Standard is proposing to keep a central register of all projects that submit for verification. There are a range of reporting templates to facilitate this.
Status of the Standard
The document reads quite like the Building Regulations and associated Approved Document, attempting to describe unambiguously what must be done for as many scenarios as possible.
The current status is voluntary. Practitioners and clients might choose to use The Standard or not.
The Standard is in the pilot version, effectively being beta-tested. It is anticipated that the content will change and develop over the coming months to respond to the beta testing findings.
We assume that a key aim for the Standard is for it to become legislation, for example, incorporated into the Building Regulations
Gaining further insight into future developments
In addition to the items described in the 'characteristics considered' section above The Standard requires projects to measure, calculate and report on a range of other issues such as potable water use, lifecycle embodied carbon, embodied carbon with standardised carbon coefficients, peak power demand etc.
In this version of the Standard, these issues do not have limits or targets, but they might do in future versions.
Top tips for using the document
The Standard is a lengthy, complex document that takes some time to understand. The following tips can help you get up to speed:
- To quickly find out what the mandatory design requirements are search for the string "pass/fail metric”
- To find the values of the various targets e.g. operational energy, embodied carbon, renewable electricity, etc. look in Appendix A.
2. Some initial comments on the proposals
Aspects we think work well
In general, we’re right behind this initiative (and were involved in its development), in particular, we like the following aspects:
- Operational energy and upfront embodied carbon targets for a wide range of building types are included.
- Different targets for new build and retrofit.
- The way that operational energy targets get harder if one does the work years in the future, incentivising the owners. of existing buildings to act quickly (because they get easier targets for the next 25 years).
- Targets for on-site renewable electricity generation.
- Fossil fuel exemptions for life safety backup systems.
- Considering refrigerant gas leakage emissions as an individual metric.
- Carbon intensity targets for district heating systems.
- Consideration of building peak electrical demand.
Aspects recommended be considered for further development
- Targets or guidance for community-type buildings.
- The operational energy targets for offices seem like they should be more ambitious.
- The operational energy targets for primary schools look like they might need to be less onerous.
- The refrigerant gas GWP limits should be more ambitious.
- Getting the right balance between high standards, completeness and uptake is a major challenge. It’s vital to keep the costs for clients as low as possible. Bearing this in mind, it’s recommended to consider how the requirements can be simplified and reduced whilst retaining the essential elements, such as the following points.
- Consider making it optional to provide the reporting of the issues without targets, for example: potable water, embodied carbon variants, electricity demand management, etc.
- Consider how to simplify the process but still have value for very small projects < 200m² GIA.
- Remove the requirements to space heating and cooling delivered limits, change it to design guidance/optional relating to how to achieve the project operational energy targets.
- Include targets for building peak winter electricity demand (W/m²), which may make use of guidance on peak heat demand.
3. Examples from our projects
Image
Text
The measured energy performance for two years are 45 and 46 kWh/m² GIA/yr which (just about) meets the proposed 2025 New Build limit but doesn’t meet the limits for projects built after 2026. It seems this might be an issue and the target might need to be less onerous.
That said, the PHPP modelling does suggest that it might be possible to reduce energy demand associated with hot water production if using ASHPs rather than direct electricity and potentially some improvements if ICT equipment becomes more efficient. However, the feasibility of achieving these is somewhat debatable.
Very low GWP heat pumps
We’ve delivered numerous projects using heat pumps with very low GWPs. For example, Wolfson College uses R744 (CO2) air source heat pumps with GWP =1.
Text
Furthermore, we have a growing number of Max Fordham staff who’ve opted to fit their own homes with R290 (propane) air source heat pumps with GWP =3.
These natural refrigerant design solutions have embodied carbon emissions (associated with refrigerant leakage) hundreds of times lower than the target set out by the Standard.
It won’t always be possible to use natural refrigerants on all projects, but we think in many cases it will be.
Perhaps the Standard's approach could be developed to require projects to use natural refrigerant unless they meet one or more exemption criteria, similar to the way the on-site renewable energy targeting works.
Image
