Building performance evaluations (BPEs) are becoming an increasingly important part of construction work. They allow project teams to consider factors which might impact the health and wellbeing of occupants and are an essential tool in identifying and addressing any performance gap between the design and actual energy performance of buildings. For this reason, BPEs form a key part of the work to decarbonise our built environment both for new build, and refurbishments. They are also a necessary part of new standards and specifications including the Retrofit Framework laid out in PAS 2035: 2023 and PAS 2038: 2021.
At present, however, there are several different BPE methodologies, each with slightly different approaches. This lack of consistency can make it challenging to cross compare between different buildings and provide useful information to owners and occupiers. To address this, the British Standards Institute (BSI) has introduced a new British Standard, BS 40101: 2022, designed to provide a clear uniform approach to BPEs.
What is BS 40101?
BS 40101 provides a clear specification for carrying out building performance evaluations in occupied and operational buildings.
It looks to mainstream BPEs by providing a single, versatile process which can be used across a range of buildings at different use stages. It is hoped this will allow project teams to gain a more accurate understanding of how their buildings actually perform in the real world, and where improvements can be made. It is also designed to give building owners and occupiers greater confidence in the performance of their building.
The standard covers:
- The planning of BPE studies for new and existing buildings.
- A process for identifying what type of BPE is required for a project.
- What data needs to be captured and how this should be recorded.
- A set of normalised performance parameters to be derived from the data.
- An evaluation process to allow the comparison on a project with similar reference cases.
- Clear roles and responsibilities for the Building Evaluator.
When should BS 40101 be used?
BS 40101 can be used to support a variety of processes including:
- The design, specification and construction of new buildings – linking into the RIBA Plan of Work.
- Guiding energy retrofit processes on existing building under PAS 2035 and PAS 2038.
- Insurance assessments of buildings.
- Reviews of the condition of properties by bodies such as housing associations who have responsibility for the welfare of occupants.
- General assessments of building stock to compile statistics such as fuel poverty.
In the future, it could also help to support new approaches to driving energy retrofits such as mortgage products which provide improved rates based on the energy performance of a home.
Does BS 40101 require a BPE for each building?
The standard states that for multiple similar buildings – referred to collectively as a cohort – additional evaluative data is gathered on a sample for an Early Occupation BPE or an in-use BPE. This deeper understanding that is obtained on a sample through the BPE enables the evaluator to assess whether the buildings are representative of the whole cohort.
What types of building performance evaluation are covered in BS 40101
BS 40101 includes three main types of BPE:
Early Occupation
New buildings and ones that are undergoing significant construction work will need an Early-Occupation BPE to spot any issues that may emerge. These BPEs may involve evaluating the servicing or set up of appliances, or challenges of use, such as poor handover information surrounding the indoor environmental controls. The early occupation period is classed as the first 3 months of a building’s use.
In-use
An In-use BPE is conducted on buildings or cohort samples before improvement works, for example, to inform the planning of large-scale retrofit or refurbishment programmes. They also constitute the ‘before’ comparison prior to the renovation. This BPE is carried out over a 12-month period at any time during the life of a building, so long as it is occupied.
Investigative
Investigative BPEs covers the tests and measurements that go beyond the BPE (either Early-Occupation or In-Use) to investigate specific aspects of performance in more depth. They are essentially a means of troubleshooting any problems identified in either the Early Occupation or In-use evaluations. As such, they typically follow after an Early Occupation or In-Use BPE and may be carried out on buildings which did not form part of the evaluation sample set.
