More on this topicNet zero carbon buildings standard to launch by end of 2025  The NZCBS or ‘the standard’, was issued in draft as a ‘pilot’ version last September. The standard is voluntary and is designed to guide the UK’s built environment towards net zero carbon buildings by 2050 through a series of energy and carbon emissions targets or ‘limits’ for construction projects. These limits reduce year-on-year as we approach 2050. The standard has the potential to transform carbon reduction across the built environment industry by giving a framework for emissions reduction. But it is currently held back by several serious flaws. These are possible to fix, and I believe that these improvements will help make the standard more accessible, more usable and more consistent with the UK’s 2050 trajectory to net zero carbon.   The first three letters ‘NZC’ or ‘net zero carbon’ suggests a focus on carbon. However, the standard’s focus is on energy use, plus construction or ‘upfront’ emissions. It is proposed that this will change in the future to ‘lifecycle embodied’ emissions, but at no stage will there be limits for ‘whole life carbon’ (WLC) – in other words, for the total greenhouse gas emissions associated with a building throughout its entire life cycle, encompassing both embodied and operational emissions.Advertisement The standard appears to deliver on whole life carbon – but actually doesn’t This is both illogical, because the standard asks for the information necessary for WLC to be reported, and confusing. It puts the standard at odds with the intent of the RICS whole life carbon professional standard (RICSPS), and the way carbon reporting is evolving across the built environment industry. The standard has numerous references to the RICSPS and in fact specifically states ‘The standard covers the whole life cycle of a building…’ but then fails to pull this together. This is inherently conflicted. The standard appears to deliver on WLC – but actually doesn’t.  The solution is for the standard to focus on two limits for every project; energy use, measured in kWh, and WLC, measured in kgCO2e. This would ensure that minimising energy use and carbon reduction are on an equal footing for every project. There would also be continuity between design stage assessments, which are WLC-focused, and post-completion assessments. Such reform would also ensure that the limits in the standard for the built environment align with both the UK’s net zero carbon trajectory, and national energy efficiency requirements. Crucially these two limits would be simple, clear and comprehensive.  WLC reporting has the benefit of being a clear concept that answers the simple question ‘What is the carbon cost of my building?’ Strangely, the standard asks for all the elements of WLC reporting but does not then require them to be aggregated, nor does it provide limits. The current ‘upfront embodied only’ limits distort the design process, as they embed short-term thinking. Advertisement Further, the separate limits for energy use and embodied carbon promote siloed thinking. These two strands must be brought together to optimise carbon reduction and resource efficiency over the entire life cycle of a building. WLC assessment and reporting specifically promote this holistic approach.   Another key improvement would be to have a single combined limit for both new build and retrofit for every use type. In the pilot version, the standard has separate limits for retrofit and new build. This unintentionally encourages demolition. The emissions costs per square metre of comprehensive retrofits can be very similar to new build. However, in the standard the retrofit square metre limits are up to 30 per cent lower than new build, making them more difficult to achieve. Therefore, where there is a choice between an extensive retrofit, or a new build, it is easier to get compliance by choosing the new build route. In this scenario, a new build will comply whereas a retrofit will fail Separate limits prop up business-as-usual and present an opportunity for those who wish to demolish because it allows them to game the system. They would achieve this by showing that a maxed-out retrofit scheme will not meet the standard’s retrofit limits, whereas a new build will meet the (easier) new build limits. In this scenario, a new build will comply whereas a retrofit will fail. In reality, retrofit is almost always the lower carbon route and should be encouraged. A single WLC limit would make retrofit the easier route to compliance and would also have the virtue of simplicity and clarity. The pilot version of the standard has a complex series of adjustments for different retrofit scopes which would all become unnecessary. It may superficially seem sensible to have separate limits, but this is not born out by practical experience.  Another issue that is not addressed at all by standard is the comparative total carbon costs of a retrofit vs new build on a given site. The standard focuses on square metre rates (kgCO2e/m²). What this ignores is that it is the total carbon emissions of a development that really matter. Invariably, the reason for demolition is to develop a new building that is much larger than the existing. This means that even if the square metre rate for a retrofit was higher than the new build, the retrofit may still be lower in terms of total emissions as the scheme will be smaller. In addition, whatever the carbon emissions, reuse of buildings is generally a much more resource-efficient and circular approach, compared with new build.  My suggestions would help make the standard less complex, more accessible, and more relevant. The pilot version has several areas that I believe are unnecessarily complicated and consequently are a barrier to take-up. For example, there is a section on ‘RPEP’, ‘ERP’ and ‘ORP’ (do you know what these are?) which is very complicated and difficult to understand and surely could be simplified. It would also be less confusing if the standard aligned directly with the RICSPS, rather than having a number of divergences. These discrepancies just confuse and undermine the consistency and authority of WLC assessment and reporting. This is detrimental to the goal of maximising carbon reduction. The standard’s assessments only take place once a building is operational, which is quite a burden for bother owner and occupier. The standard should therefore be made as accessible and as simple as possible or it won’t be used. Only a major edit will resolve these issues.  For a more detailed analysis of the NZCBS, see www.TargetingZero.co.uk Simon Sturgis is a leading authority on whole-life carbon design who served on the carbon accounting task group developing the Net Zero Carbon Building Standard   2025-04-25 Simon Sturgis comment and share