Building Performance Evaluation (BPE)* shouldn’t be treated as an extra, it needs to become an integral part of the design process. But what exactly is it and how should we be doing it?
BPE is becoming far more common because there has been significant increase in funding** and its inclusion in RIBA’s Stage 7 has signalled to the design profession the importance of fully integrating BPE into the design process. However, despite its inclusion into RIBA’s work plan, there is still some confusion over the actual process of undertaking a BPE. So what is it and how should we be doing it?
BPE is not a new idea. Many other industries invest time and resources evaluating the end product, notably manufacturing where this process gave rise to ISO 9000. By checking their products against a series of metrics, such as length, weight, or finish, manufacturers can keep an eye on their processes and ensure that the end product continues to meet the brief. Of course the manufacture of 100’s or 1000’s of identical products makes this process of evaluation far simpler than evaluating the inherently bespoke buildings that we create, but the principles of self-evaluation are essentially the same.
Many firms will already undertake an informal BPE in the form of a “lessons learnt” review, using interviews and walkthroughs to get a sense of the building's success. These studies are very useful, but the informal approach makes it difficult to translate the findings between projects, with the collection of data often limited to only a few occupants and perhaps focused on specific aspects of the scheme. This inability to translate lessons between projects creates a risk that the findings will stay within a small project group, preventing benefits to the wider practice.
Formalising the process can overcome some of these barriers to dissemination and this is where a BPE really stands apart from a traditional “lessons learnt” review. Using robust analytical techniques creates a transparency that enables anyone to understand the results. This then generates greater confidence in how these lessons can be applied to their projects. These techniques do not have to be much different or more complex than those already widely used. Typically they will include interviews, walkthroughs, questionnaires and environmental measurement. By anchoring these tools within a defined process or framework, projects can be directly compared not only within one firm/practice, but also across disciplines and the wider industry.
This defined framework of the BPE does not have to be prescriptive, but instead can be designed to set up the process of evaluation, focusing on the occupants and the energy use, and then the interplay of the technologies employed in the building. The occupant satisfaction and the energy consumption are the outcomes of the building and understanding how the building affects these outcomes is the crux of BPE. The BPE can thus be designed as a two-step process:
1. Understand the outcomes (occupant satisfaction and energy consumption)
2. Determine the impact of the building on the outcomes
There is a tendency for BPE studies to be very technical, measuring every conceivable aspect of the built environment, but we need to understand what this technical data will tell us about the building and its performance. These technical measurements should be used to support the attitudes of the occupants or explain the energy consumption, providing an extra dimension of understanding. For example our work at Brighton Aldridge Community Academy (BACA) found that the occupants felt the hall area was cold, which prompted a focused investigation into conditions and highlighting a problem with the fresh air control system. Measuring the temperature of each space in a large school, such as BACA, would have given us a great picture of the whole building, but we might not have realised the impact of the low temperatures in the hall on the occupants. BPEs should not be generating data for data’s sake, but should be telling us the story of the building and this is very hard without understanding the outputs.
BPE studies pave the way for truly sustainable buildings, not just in terms of energy, but also in terms of social sustainability. The findings from BPE studies provide hard evidence we can build on and can help to create a cycle of continuous improvement that has benefits far beyond individual schemes and impacting the wider environment
Joe Jack Williams
You may also be interested to read:
‘Measured Response’ by Peter Clegg, RIBAJ November 2015
* Building Performance Evaluation (BPE) is a form of Post-Occupancy Evaluation (POE) which can be used at any point in a building's life to assess energy performance, occupant comfort and make comparisons with design targets.
** Due to the push from the well-funded Innovate UK BPE programme continuing the exemplary work of the PROBE studies.
Image: Brighton Aldridge Community Academy ©Tim Crocker