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Our experience of NABERS UK so far – Part 2

In April 2021 I joined the NABERS UK Independent Design Review (IDR) panel. The panel members are responsible for carrying out formal reviews of NABERS Design for Performance (DfP) projects to assess whether the building is likely to achieve its target rating in practice.

We, at Inkling, have seen a lot of interest in this new service.  I have completed 7 IDRs now with several more scheduled.

In March 2023 I wrote about our experience of NABERS reviews so far. This is an update with further thoughts on the process and what we’ve learned.

A fan coil system with separate outside air modelled in IES VE software

Quality of modelling is key – the model provides an estimate of in-use energy and, resultingly, the building’s potential NABERS UK rating. Therefore it is key to the DfP process that any recommendations related to the modelling should be addressed as a priority to ensure there is confidence that the rating can be achieved in operation. The designed building and its systems should be represented accurately. For example, actual design ventilation flowrates should be used in the model and not defaults as this would lead to inaccurate fan energy usage.

Prioritise actions – the independent design review will generate a large number of recommendations. It is therefore crucial that the reviewer identify which of these recommendations are most important in achieving the targeted NABERS rating. It is also likely that some recommendations will not be able to be implemented on this project and may instead act as design guidance for future projects, which is in line with NABERS’ role of bridging the performance gap between design and in-use energy performance.

Be clear about next steps – after the formal IDR has been carried out it is important that the reviewer ensure that the design team are clear about both what the next steps are and who is responsible for completing each of them. A document summarising the next steps and clarifying important actions is helpful, alongside a meeting to discuss this and answer any questions raised by the IDR.

Keep up the momentum – the clear actions and recommendations outlined in the previous step help to progress the NABERS process but it is still important to keep up communication with the design team and ensure that there are no unforeseen blockers delaying the process. Timescales vary between projects and for projects with longer timescales there may also be some re-calibration required within the IDR recommendations as knowledge develops. For example, where a clarification or formal ruling has been made by NABERS UK.

Cover of the NABERS UK Guide to Design for Performance Version 2.0

Guidance versions –we have recently seen the release of NABERS UK version 2.0, which incorporated guidance covering the whole building and tenancy ratings. Aside from a correction to the modelling margin calculation, there were no changes to the base building rating guidance. However it is possible that future updates to NABERS UK may incorporate more substantial changes. Therefore, the management of version changes should be considered in the DfP process, particularly considering that for some projects the DfP process takes some months and may span guidance versions. Although there will be a transition period for updated guidance, the review process may not be concluded during this time.

We are all learning – NABERS UK and DfP is a relatively new scheme and a major, and exciting, departure from compliance-based design into performance-focused design. As this is a novel scheme (for the UK), there are many lessons left to learn and this learning phase will continue for some years. In the next few years, as DfP Design reviewed projects have their in-use performance rated for the first time, the findings can be fed back into the DfP process to make it more robust.  For the IDR panel members, learning includes calibration between previous and current IDRs to ensure consistency, clarification with NABERS/ BRE on areas where the documentation is not clear and discussion with other IDR panel members to ensure consistency between reviewers.

If you would like to talk to us about your NABERS UK project and how we can support you then please get in touch with us at

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