Glass building in front of clouds
The so-called ‘performance gap’ measuring the difference between how a building is designed to perform and how it actually behaves is a well-documented problem that has plagued the industry for years.
In 2011, a study of 28 buildings constructed under the Department of Energy and Climate Change’s Low Carbon Buildings Programme, carried out by the Carbon Trust, found that operational energy use was up to five times higher than estimates during design. Furthermore, 75% of the designs did not perform as well as expected when compared with industry benchmarks.
Given that buildings contribute about 25% of total UK greenhouse gas emissions, it is critical that future waves of low carbon buildings perform as intended to keep the nation on track to meet a legally binding target to hit net zero by 2050.
Verification is a key part of the problem, with building performance measurements based on theoretical design-stage models and predicted emissions data. When specification choices for many products, materials and systems have not yet been made.
A new technical standard, the UK Net Zero Carbon Buildings Standard (UKNZCBS), aims to tackle this issue and bridge the performance gap by imposing limits on operational and embodied carbon that are verified based on real-world building data.
Developed by a technical steering group including RICS, RIBA, CIBSE, IStructE and LETI, with input from more than 350 experts, the voluntary standard (launched in March) requires one year of metered data after a building is fully occupied. Furthermore, embodied carbon is assessed using measured quantities rather than design estimates.
Surveyors in various roles will be critical to the success of the UKNZCBS. They are needed to measure the performance of projects applying for net zero status, verify compliance, and get building owner and building manager clients onboard with the new standard.
Fabrizio Varriale, place and space analyst at RICS, says: “Surveyors providing advice on property and managing assets are in a good position to say, ‘this is the way to demonstrate we are doing our bit for the climate’. And in a way recognised by the rest of the industry that is much better aligned with our carbon targets than other schemes.”
Building consensus
The UKNZCBS builds on the work of previous collaborative initiatives, such as the Net zero carbon buildings: A framework definition and the Net zero whole life carbon roadmap, to create the UK’s first single, agreed methodology to define net zero buildings.
The Standard outlines science-based limits, targets and reporting requirements for new and existing buildings, aligned with the national commitment to limit average global temperature rise to 1.5C above pre-industrial levels, also accounting for the future decarbonisation of energy supply.
The UKNZCBS builds upon existing standards by combining real data on existing building performance with a new methodology that defines the built environment’s allocation of the UK’s national carbon budget. This was further broken down into specific limits for each sector of the industry, such as commercial and residential property.
“It means we've been able to look at what's actually feasible based on real building data and what's necessary to stay within the carbon budget,” says Katie Clemence-Jackson, CEO of Net Zero Carbon Buildings Standard – the company set up to own and manage the Standard. “It’s not a magic formula, quite a lot of judgement had to be applied to set those limits, we've had to think about the pathway for the whole built environment, uptake and the trajectory of adoption over time.”
Performance levels set out in Version 1 of the Standard cover the whole carbon lifecycle. Maximum limits are imposed on upfront emissions involved in manufacturing and construction, and on annual emissions from energy consumption during building operations. Participating organisations must also exceed minimum targets for on-site renewable electricity generation.
The methodology for measuring energy and carbon is based on RICS' Whole life carbon assessment for the built environment and thresholds vary based on whether it’s a new build or a refurbishment and on building type. For example, maximum energy use in a new build office starting in 2026 is set at 88kWh/m2 per year, and for a new primary school it is 45kWh/m2 per year. Limits become more stringent over time to align with the UK’s 2050 net zero targets. For example, the office limit is set to drop to 45 kWh/m² per year by 2040.
Evidence needed to support a building owner’s claim that their asset is net zero compliant will be gathered and assessed by various construction professionals, opening up various opportunities for chartered surveyors.
“Completing an embodied carbon assessment means having as-built quantities of materials, which surveyors will collect as part of the quantity surveying service,” says Varriale. Similar to EPC assessors, professionals including surveyors, may provide services verifying compliance with the Standard, or verifying a particular aspect of the claim made through the application. For example, operational energy or embodied carbon.
Varriale notes that surveyors in the role of facilities manager or asset manager may also be involved in providing detailed breakdowns of energy use and energy bills – required as part of the reporting process for operational energy, depending on the building type.
Surveyors providing advice on property and managing assets are in a good position to say, ‘this is the way to demonstrate we are doing our bit for the climate’.” Fabrizio Varriale, RICS
Real-world trials
The pilot version of the standard was put through its paces on 216 projects over a four-month period last year. It had input from developers, designers and building owners, to understand the challenges and how it could be adapted ready for the launch of Version 1, which was published in March.
According to Virriale, participants in the trials felt that limits on upfront carbon and operational energy were achievable, but there was some variation across different building sectors and building typologies.
“Some signalled difficulties where a building has special uses that increase energy consumption, for example tech buildings with a lot of special equipment that increase energy demand,” says Varriale.
The trials revealed concerns over how the Standard should be applied in sectors where there are different areas of responsibility for managing buildings. For example, in the office sector there's often a split between landlords and tenants, with neither party having control over the other’s space.
Version 1 of the UKNZCBS delineates between landlord and tenant spaces when claiming to become a net zero carbon building, whereas the pilot version only allowed applications for an entire building.
According to Clemence-Jackson, others in the trial experienced difficulties gathering metered data to demonstrate energy use, particularly in the homes sector due to data privacy concerns.
Challenges were also uncovered around information handover, and which professionals are responsible at different work stages. “There were some concerns around the contractual implications of being able to meet performance in use when construction contracts are often set up to handover at a particular point and when the in-use phase is governed differently,” says Clemence-Jackson.
While the pilot outlined how verification might work, Version 1 of the Standard introduces third-party verification to provide clear and indisputable proof that a building is net zero carbon aligned: an objective of the Standard since its inception. The verification administrator will also develop a training and accreditation scheme that will open up verification services to the wider industry.
Among other modifications introduced is a process of ‘equivalence’ that will enable the application of other schemes and standards, such as NABERS UK or Passivhaus to demonstrate that certain requirements of the UKNZCBS have been met.
Furthermore, alongside evidence of measured performance after at least one year of occupation, introducing ‘validation’ at practical completion will ensure a building is on the right track to achieving the Standard. “We received a lot of feedback, particularly from the commercial sectors, that to get funding for buildings and to lease them, it is important to be able to say, at the point of handover, that they are on track to achieve net zero,” says Clemence-Jackson.
Ambitious low carbon building standards are an important catalyst for industry change, but a lack of political consensus around climate change policy in the UK could be problematic if, for example, a change of government were to occur at the next general election. Both Reform UK and the Conservatives want to scrap net zero by 2050 and the Climate Change Act 2008.
“Whatever the political discussions, it doesn't change the science of climate change, which is becoming increasingly noticeable in the UK through things like extreme weather events,” says Clemence-Jackson. “The industry has come together for this Standard, which shows there's an appetite and a demand for it. Regardless of political developments, we know that momentum is not slowing.”
