The British Standard everyone should be talking about


Industries such as aviation, car or phone manufacturers would never think of developing a new product without understanding the performance and weaknesses of previous models. So why is it that the construction industry is so bad at examining its products in use and learning from them?

What is Building Performance Evaluation?

Building Performance Evaluation (BPE) refers to the analysis of a building’s performance across numerous parameters such as energy use, CO2 levels and user comfort. Going also by the term Post Occupancy Evaluation (POE), Building Performance Evaluation refers to the evaluation of a building’s performance across numerous parameters, typically over a period of time. BPE distinguishes itself from POE because you don’t need to wait until the building is complete to begin the process. At Architype we have been using evaluation to constantly improve how buildings work and to help avoid the typically woeful industry-wide performance gap. This gap can be summarised by the performance targets estimated at design stage that are rarely achieved once the building is in use. For example, research commissioned by Innovate UK in 2016 illustrated that the performance gap in non-domestic UK buildings was two to ten times greater than the design intent; we simply cannot afford to allow performance gaps to continue if we are going to achieve climate targets.

In our experience, it is much more effective to commit to evaluation from the outset of the project to deliver a high performing building. One that doesn’t waste energy or resources, that isn’t costly to maintain, and is a delight to experience, with great acoustics, natural daylight and fresh air.  

From my own industry experience, I have seen evaluation techniques being invaluable at analysing the existing building stock of a client, or selected precedent projects, to inform a tailored and rigorous project brief. This is because it more accurately establishes the ultimate spatial and performance requirements – i.e. how much energy do you want to use or how much space do you need for certain tasks.

So if BPE is so powerful, why don’t we see it being used more? This is partly driven by concern amongst some about unearthing defects or performance shortfalls. However, if problems exist, they are there irrespectively and proactively managing them can result in lower overall impact in the long term. Helping to identify these can prevent minor defects from accumulating to become significant problems e.g. unnecessary operational costs or damage from water ingress.  

For more of an introduction into what Building Performance Evaluation offers, take a look at our new one-pager. 

Graph of seven years’ energy monitoring of the exemplar Enterprise Centre, UEA, showing the variation in usage of Energy Use Intensity between 43.3 – 66.6 kWh/m2/yr.  These results give all seven years a DEC ‘A’ rating, and for comparison it should be noted that best practice energy for existing university buildings is roughly four times greater at between 162 -223 kWh/m2/yr (NZCBS CIBSE analysis). 

Building Performance Evaluation and Net Zero Carbon

With the international pursuit of net zero carbon solutions, it is inevitable that the next decade will see many new ideas being explored to reduce both operational and embodied impacts. Building Performance Evaluation offers the key to evaluating whether these efforts hit the targets we need and offer clients and project teams a robust process to demonstrate that their buildings ‘walk the talk’.


The publication of the British Standard 40101 (BS40101) in 2022 has brought a much-needed standardisation, providing confidence to clients and highlighting what they can expect from Building Performance Evaluation. It establishes three tiers of scope; Preliminary, Light, and Standard, clearly outlining the activities both for evaluating individual buildings, and cohorts of buildings – ideal for estate-wide retrofit evaluations. We’ve created the workflow diagram below for communicating to clients how we sequence these various activities.    

An example workflow of activities for the qualitative aspects of Building Performance Evaluation, as supported by the requirements of the British Standard 40101. A separate workflow captures the longer-term requirements for quantitative environmental monitoring. The standard allows flexibility to tailor evaluation to exactly meet client needs. 

Even more powerfully than this, BS40101 provides an approachable ‘how-to’ manual of undertaking evaluation and should be seen by the industry as a powerful enabler in getting buildings to work better. It demystifies what evaluating building performance consists of, splitting tasks into qualitative studies like user feedback workshops, and quantitative studies like energy meter readings and CO2 monitoring, as demonstrated on our initial Passivhaus schools here.  

We have been using the BS40101 standard on current projects including the analysis of three recently completed primary schools for the City of Edinburgh Council who have used the findings of evaluations across their schools to iteratively inform the briefs for the next generation of schools. Findings spanned how and why spaces were being used in alternative ways to their design intent, including implications for procurement decisions, and the environmental characteristics and performance of spaces and systems. 

Multiple user workshops of three Primary Schools for the City of Edinburgh Council: the same questions were put to a range of building users to gather views on a variety of bespoke and standard topics. 

Beyond the three established tiers are a wealth of investigative BPE options that BS40101 outlines, intended to support further bespoke evaluation into specific building aspects which may have only come to light through the initial programme. For example, BS40101 can be deployed in various permutations to align with specific objectives such as the relationship between perceived user thermal comfort, heat demand data, and in-situ U-value measurement. We have employed these investigative options on our completed projects, such as using an array of sensors paired to our cloud-based portal allowing clients and our designers to quantitatively understand performance in use and help identify optimisations. This was recently deployed at the Welshpool Church in Wales Primary School where the small power energy usage was able to be halved, contributing towards achieving savings of £60,000 a year in running costs when compared to a typical school in the area.  

Example from Architype’s cloud-based portal for environmental monitoring, showing Example from Architype’s cloud-based portal for environmental monitoring, showing our Hereford studio. This portal is used as a client-facing and designer-supporting tool on a range of recent projects and our studios and allows snap-shot overviews of temperature, humidity and CO2 levels, along with Excel exports for detailed analysis. 

Next steps for the industry

Standardisation of evaluation means that workflows, techniques, and lessons learned can be applied and shared more consistently, supporting vital industry progress. We have already seen it provide greater clarity to clients, and we hope that it can also help more designers and consultants begin providing this service and learning from its powerful findings.  

We believe the British Standard 40101 has the potential to increase the uptake of evaluation across the built environment to support the outcomes we need to achieve, both for people, but more importantly for the planet.  

Seb Laan Lomas is an associate, Passivhaus designer and member of our Perform+ consultancy team. If you are interested in discussing how Building Performance Evaluation could help optimise your projects or assets, our Perform+ team are happy to help. For a free one-hour chat about your challenges and opportunities, please contact:

More information

For those interested in learning more, the Built Performance Network is a valuable community, membership organisation, and one-stop-shop of resources, Energy People Buildings is a highly informative book, and RIBA has published numerous guides over the years including the Plan for Use guide.