The UK Net Zero Carbon Buildings Standard Guide: Part 11: Carbon offsetting

MEng
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:
The new UK Net Zero Carbon Building Standard sets targets for the amount of renewable energy generated on site. Energy can be generated by either Photovoltaics (PV), Wind Turbines, or Hydroelectric Turbines, but PV will be the relevant technology for the vast majority of buildings.
Targets are expressed in terms of generation per m2 of building footprint per year. This means that a 50-storey and two-storey building with the same footprint have the same generation target.
The targets vary depending on region, and building use:
Single Family Homes and Single-Storey Storage and Distribution |
All other Building Types |
|
Scotland |
60 kWh/m² FP/yr |
30 kWh/m² FP/yr |
Middle/North England, Northern Ireland, Wales |
65 kWh/m² FP/yr |
40 kWh/m² FP/yr |
South England |
75 kWh/m² FP/yr |
45 kWh/m² FP/yr |
As an example, a London office building would be required to generate 45kWh/m² FP/yr. Assuming a modest solar irradiance and panel efficiency, this would require around 28% of the building footprint to be PV. This seems to be an achievable value for the majority of buildings.
The Standard does make an allowance for situations where achieving the targets would not be possible, and will accept reduced targets for the following reasons:
If a reduced target is to be used, a statement is to be issued providing justification with appropriate supporting calculations.
The Standard also requires that PV systems have an upfront embodied carbon of no more than 750kgCO₂e/kWp. kWp (kilo-watt peak) is the measure of peak array electrical output. There is no limit for wind turbines or hydroelectric turbines.
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The upfront carbon limit of 750kgCO₂e/kWp seems like it could be reduced. It’s recommended that The Standard consider reducing this in the future.
Attempting to assess upfront carbon compared to lifetime carbon abated for renewable energy generators isn’t trivial (and actually not possible using RICS LCA type approaches) due to the number and type of interrelated influencing factors. However, one can get a feel for the relative impacts of different technologies by looking at other published reports such as the work by Pehl et al published in Nature Energy, and excerpt from which is shown below.
Embodied energy use of electricity production as a percentage of lifetime electricity production. Global average values are shown by secondary energy carrier (coloured bars) for capacities built in 2050. Combined model variations over both regions and technology variants (sample minimum, 25th percentile, median, 75th percentile, and maximum, see Methods) are shown as grey boxplots. Adapted from Pehl et. Al. Nature Energy Article Article Published: 08 December 2017.
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