BS 40101:2022 Introducing a first British Standard on evaluating building performance

We’re launching a new standard this month on building performance evaluation. This blog post explains the thinking behind the standard’s creation, what it contains, and why it will be valuable to a host of users.

BSI’s newest standard was first proposed by the Retrofit Standards Task Group, a body set up by BSI as the standardization work-stream of the Each Home Counts review. Each Home Counts was a government-commissioned review of consumer advice, protection, standards and enforcement in relation to UK home energy efficiency and renewable energy measures. It asked how consumer decisions are supported when they seek to install measures, and what ensures the right measures are fitted in the right way.

Building on the review’s recommendations, the Retrofit Standards Task Group identified the need for a standard that simply gives well-considered and comprehensive guidance on how to evaluate the energy efficiency of existing buildings. But at the same time it seemed to make sense to include evaluation of new buildings as well. Thereafter it was also felt that building evaluation should include not just energy performance but other facets of performance, including how buildings affect their occupants. Pioneering work had already been done on how to assess indoor environmental quality as it affects the health and well-being of building occupants and building fabric. The decision was made to incorporate this content in the new standard. The result is: BS 40101:2022 Building Performance Evaluation.

Guidance on how to evaluate building performance

BS 40101:2022 has a simple aim: it gives guidance on how to evaluate building performance. But this is a complicated area. Thus the standard covers the what, why, when, how and who of building performance evaluation.

“What” relates to what needs to be tested or evaluated depending on the physicality of the property, the performance parameters of interest and the reason or reasons for the evaluation. Which brings users neatly on to “why” evaluate performance in the first place. This must be determined. Is it to verify performance or measure performance before or after improvement works? To investigate suspected underperformance or to inform the design of a new building or building type? The standard also gives guidance on tracking performance over time, e.g. for annual reporting or periodic building MOTs.

“When” is another question that needs to be answered. Evaluation activities may be conducted before works, “in process”, at completion of works, or 6-12 months after completion. They may be triggered by construction stages, a prescribed timetable, to aid the specification of other building(s) and/or if performance concerns are raised by occupants, users or other stakeholders.

Next is “how” the evaluation should be conducted and escalated if required – including ongoing adoption of new methods, technologies and techniques. The standard also prescribes the accuracy, granularity and format in which test and measurement data should be captured and held.

Finally “who” outlines the expertise required to conduct and interpret evaluation activities and to take responsibility for checking the relevant performance parameters and investigating any underperformance found to identify the root cause. 

The standard also takes account of building occupants/operators and occupation patterns including density, both in evaluating that the building performance is fit for purpose in respect of its occupants and occupation and in incorporating occupant (user) feedback and insights to identify and help investigate performance concerns. 

Important benefits

Once deployed, it’s envisaged that BS 40101:2022 can help deliver a number of important benefits. For one thing, this standard can help tackle a major issue in the built environment which is determining the relative influence of design versus built performance in construction projects, known as the performance gap. This knowledge can help drive efficiency and productivity.

This new standard can in addition help to progress the transition to net zero and support sustainable growth by identifying and verifying more sustainable buildings; driving improved energy efficiency; informing the design of new buildings and the retrofit of existing buildings; investigating underperformance; providing data for ongoing measurement and monitoring to optimize performance; and helping promote a wider understanding of building energy efficiency performance.

In addition, BS 40101:2022 can help drive improvements in the health and well-being of building occupants; help users develop expertise in building evaluation; improve the efficiency of building evaluation; and better manage risks in relation to building evaluation.

All told this is an important and wide-ranging new tool for the construction industry and design professionals to work with.