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The recently published net zero carbon buildings standard is hugely ambitious in its scope. More than 350 people from all corners of the industry were required to create it and, uniquely, it has set out to align the emissions from buildings with the Paris climate agreement goal of limiting global warming to 1.5°C.

A built environment carbon budget to keep warming within 1.5°C was determined and allocated across 13 building sectors. This is far more than any other net zero scheme, most of which focus on offices, residential, schools and retail.

The standard’s sectors also include science and technology, cultural and entertainment, healthcare and datacentres to name just a few. Embodied carbon data from 800 projects, and operational energy from 3,200, was used to determine the level of carbon performance that could be practically achieved for each sector. This was combined with the carbon budget data to set net zero carbon limits for each building sector – and these get progressively lower each year between 2025 and 2050.

The upfront carbon targets are described as tough but achievable, and recent projects demonstrate this. Eden, a net zero office in Manchester which was completed last year for a budget just 2% more than a standard office, meets the 2027 NZCBS upfront embodied carbon limit.

>> Also read: Why the industry needs another net zero carbon buildings standard 

A significant effort was made to get low upfront embodied carbon right down within the budget but, once the lessons from pioneers such as this become business as usual, meeting the limits will become much easier.

The limits are much more nuanced than those set by RIBA and LETI and the 2030 limits are less onerous too. The challenge will come later; the NZCBS upfront embodied carbon limit for an office completing in 2050 is just 60kg of CO₂/m²_, a 12th of that for 2025. The theory is that the carbon footprint of materials will drop as the grid decarbonises and manufacturing processes become more efficient. 

The standard is a work in progress; the lifecycle embodied carbon limits will be published once sufficient data is available

There are no lifecycle embodied carbon limits yet, which haas been  flagged by a blank page in the published standard. The standard is still a work in progress and the lifecycle embodied carbon limits will be published once sufficient data becomes available.

Some of the upfront embodied carbon limits will need adjusting thanks to a paucity of existing data in sectors such as science and technology and data centres. And the diversity of science and technology facilities means closer definition is needed to be meaningful; there is a big difference between a dedicated life science facility handling dangerous pathogens and a university science department with general laboratories, teaching space and offices.

The abundance of data available for offices means that the standard has set upfront embodied carbon limits for the shell and core and the whole building. As the standard develops, separate limits for the shell and core and fit-out of other building types may be set where design and construction responsibilities are split between landlord and occupier.

The standard also includes upfront embodied carbon limits for retrofit projects which is welcome as these are not generally available.

Operational energy limits are expressed in kW/m²/yr in recognition of the limited supply of renewable energy, with the limits based on a renewable energy budget for the built environment. There are limits for retrofit projects, including those retrofitted in stages rather than in one go. Like the upfront embodied carbon limits, these are stretching but achievable, and they reduce over time, although not as drastically as the reductions are based on improvements in the efficiency of building services and small power equipment.

There are limits to efficiency improvements – LEDs are already close to the theoretical maximum. ºÃÉ«ÏÈÉúTV services are already very efficient, which means that improving the efficiency of, say, ventilation systems may only be achievable by increasing the size of air-handling units and ductwork for more efficient airflow. This comes with a space and carbon cost as more space is needed for plant. The standard also requires building operators to report on operational carbon emissions.

There are targets for onsite renewable energy generation and limits for the global warming potential of refrigerants.

A potential barrier is certification is only granted once 12 months of operational energy data is available which isn’t much use for marketing a building to potential occupiers

The next steps are to establish a verification process for certification and the identifying of pilot projects to test the requirements. The data from these will be used to inform the first full version of the standard, which is expected to be ready towards the end of next year.

A building can only be certified after 12 months of operation, so it will be some time before the first certified buildings come on stream. The standard also sets limits for annual, delivered space heating. This requires heat meters which are not widely specified, which means pilot buildings are probably still under construction. That in turn means there will not be any certified buildings until 2027.

The big London developers are supporting the standard and have the resources needed to deliver buildings and go through the process to meet it. Whether it receives wider support remains to be seen – one potential barrier is that certification is only granted once 12 months of operational energy data is available, which is not much use for marketing a building to potential occupiers.

The standard will also be competing against NABERS, which offers interim certification at design stage. This currently only covers UK offices but it could be extended to other sectors relatively easily – as it already is in its native Australia – meaning much of the information needed is already available.

A building that meets the standard is described as net zero aligned. This means that all buildings must meet the standard if the UK is to stay within its carbon budget for the built environment. That is a monumental challenge – but the NZCBS is at least a good start.