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The following BSI references relate to the work on this document:
Committee reference CB/401
Draft for comment 21/30431027 DC

Foreword

Publishing information

This is published by BSI Standards Limited, under licence from The British Standards Institution, and came into effect on 31 January 2022. It was prepared by Technical Committee CB/401, Retrofitting Energy Efficiency Measures. A list of organizations represented on this committee can be obtained on request to its committee manager.

Relationship with other publications

The British Standard is the first in a series of standards which address building performance. Other standards in development include:

BS 40102, Health and well-being and indoor environmental quality in buildings1) – Health and well-being in buildings
BS 40104, Assessment of dwellings for retrofit

Information about this document

This British Standard acknowledges the contribution of the Building Performance Network in developing this British Standard, supported with funding from the UKRI Transforming Construction Challenge.

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0 Introduction

0.1 General

This British Standard is concerned with the evaluation of the performance of buildings at any point during the operational stage of their lives. It provides a tailored and graduated approach enabling the standard to be used across all building types and uses and for a wide range of project or study objectives.

This British Standard uses data gathered from tests and measurements, monitoring, reported experience and observation to evaluate the actual performance of a building or cohort of buildings, and complements other standards, such as BS EN 16798‑1 and BS EN ISO 7730, which derive analytical predictions of performance by calculation and analysis of design.

0.2 Building performance evaluation

The term “buildingperformance” can cover all parameters and descriptors that capture how well the building fulfils its purpose. Buildingperformance evaluation is the term used to describe the gathering of quantitative and qualitative data that characterize the performance of a building (or separate premises within a building) and the interpretation of these data to draw conclusions regarding specific performance attributes and the overall performance of the building.

The study of the performance of buildings and the relationship amongst buildingperformance attributes, building and occupant health, occupant wellbeing, flows of electrical energy, fuel, water, CO₂ and other emissions across the building system boundary has been attracting interest since, at least, the 1970s, with the PROBE [1] studies of the 1990s being the first to report results of professional study on multiple buildings.

Interest in determining the performance of buildings has grown steadily, stimulated by increasing understanding of:

the often substantial difference between design predictions and the actual technical and functional performance of buildings (now referred to as the performance gap);
how buildings, and especially the indoor environments they enclose, affect human health, wellbeing, productivity and learning; and
how building fabric and structure can be detrimentally affected by the environmental conditions created in and by a building through its design, construction and installed services.

The demand for knowledge about the actual performance of buildings is critically important in the context of aspirations by UK and devolved authority governments to upgrade the UK’s building stock to reduce energy demand and improve indoor environments and to ensure both new and existing buildings contribute to meeting the UK’s zero carbon emission commitments.

Understandably, the growing appreciation of the significance of buildingperformance has been mirrored by a developing area of professional practice in buildingperformance evaluation, originating in academic and industrial research, and now forming a body of experienced individuals and companies providing professional services in buildingperformance evaluation (BPE) using a growing toolbox of techniques and equipment.

Over the last decade BPE has become a focus area for both The Chartered Institution of Building Services Engineers (CIBSE) and The Royal Institute of British Architects (RIBA), features in the UK Government’s Transforming Construction Challenge and increasingly underpins initiatives such as the Soft Landings Framework [2] and the Assured Performance Process [3] to deliver better performing new buildings and upgrades of existing buildings. The requirement to evaluate the outcome performance of retrofit improvements is included in PAS 2035 (for domestic scale buildings) and PAS 2038 (for larger non-domestic buildings).

Advances in sensing, monitoring and measurement technology have increased the ease and affordability with which performance measurements can be made and key parameter values monitored, providing better data on which to base buildingperformance evaluation. The roll out of smart meters and the incorporation of energy metering into renewable energy generation equipment and heat pumps increasingly provides time-stamped and time series energy data. Building monitoring systems and devices such as smart thermostats (that are being installed in some new social housing) and CO₂ monitors (since 2020 a regulatory requirement in new-build Scottish housing) herald an era where aspects of monitoring and sensing are automatically embedded within buildings.

The means and rationale for undertaking buildingperformance evaluation are now firmly established. BPE can support a wide range of stakeholders seeking to understand, verify and improve the performance of individual buildings and the wider building stock.

0.3 Why is a British Standard needed?

Whilst the number of BPE projects/studies on individual buildings and groups of buildings continues to grow, there is no consistency in how these projects are carried out and reported and in how the raw data and evaluation results are recorded and stored.

This lack of consistency means that BPE findings are often incompatible, even for an individual performance parameter, making it difficult to revisit findings or re-evaluate a building after time has passed or if a different evaluator carries out a repeat or follow-up study. This limits the benefit of aggregation or meta-analysis and often unhelpfully focuses any review and challenge of BPE findings on the methods and approaches deployed, rather than on the results obtained.

The purpose of this British Standard is, therefore, to:

enable consistency in the evaluation of the performance of buildings and the reporting and recording of evaluation findings and conclusions;
provide a basis for verification of specified performance in new and upgraded buildings in respect of key performance parameters and attributes (e.g. for “pay as you save” finance, performance contracting, performance-linked finance, and potentially for future regulatory compliance);
provide a basis for determining whether the performance specification of a new or upgraded building is achieved in use; and
provide a basis for the identification of improvement options or corrective actions (ranging from setting adjustments to extensive fabric upgrade) and the development of improvement strategies, process improvements, plans and specifications (e.g. in pursuit of transition to net zero carbon).

NOTE The Preliminary Evaluation level included in this British Standard is not likely to satisfy the purposes outlined in b) to d) although it should enable insight based on occupant opinion. Preliminary Evaluation studies carried out in accordance with this British Standard follow the same framework of planning, execution, treatment of data and reporting. Preliminary Evaluation is therefore considered a first step towards more comprehensive BPE.

0.4 What does the British Standard cover?

This British Standard covers:

the planning of BPE studies, including
1. timing: for new buildings or those subject to major refurbishment or retrofit, planning should be carried out at the strategic stage of a construction or refurbishment project (e.g. see BS 8536; RIBA Stage 0 or Stage 1, or Soft Landings Framework plan [2]); and
2. content: based on the purpose of the evaluation and the use and complexity of the building(s);
the choice of comparator cases, including but not limited to:
1. performance specification;
2. design predictions;
3. modelled design;
4. regulatory thresholds;
5. previous evaluation of the same building;
6. evaluation of similar building(s); and
7. industry benchmarks and thresholds set by quality standards;
data gathering relevant to the BPE level pursued, through documentation review, test and measurement, monitoring, experiential feedback and observations;
comparison against comparator case parameters and interpretation of individual, interdependent and whole system results;
the derivation and reporting of derived performance parameters;
requirements for data naming and retention; and
report contents and compliance claims.

0.5 Who is it for?

Whilst this British Standard is primarily for use by those carrying out BPE projects, it is also valuable for those considering or commissioning studies or aggregating findings across multiple studies.

A BPE study report provides valuable insight for many different stakeholders, including but not limited to:

specifiers, designers, commissioners/procurers and deliverers of new buildings, and of the modification, upgrade or retrofit of existing buildings;
those assessing the opportunity to improve existing buildings;
those financing construction works (as lender, grant provider/administrator, or self-funder);
owners and leaseholders of buildings and portfolios of buildings, including property fund managers, social housing providers and their investors;
building tenants and occupants;
those wishing (or being required to) disclose (or manage) the CO₂ emissions of buildings for which they are (at least partly) responsible;
NOTE This could include finance providers, corporate or public estate owners and social housing providers.
those concerned with the health and wellbeing of occupants, either through social or contractual responsibility; and
those studying the performance of the building stock to support the derivation of statistics (e.g. on fuel poverty), inform policy, devise programmes, contribute to sector knowledge and to report on any of these.

1 Scope

This British Standard specifies requirements for three levels of buildingperformance evaluation plus an additional supplementary level:

Preliminary Evaluation (PE): the lightest entry level evaluation using readily available data and information plus occupant feedback;
Light BPE: a basic BPE study and the lightest level to take account of internal environmental monitoring;
Standard BPE: a good all-round study based on more granular data enabling greater insight and a good basis for decision making and further performance investigations;
and, additionally:
Investigative BPE: allows for additional investigative elements to be pursued in parallel or following any of the three levels listed above and for all types of study to be structured, conducted and reported consistently.

NOTE 1 Elements from higher levels of study can be added to any of the lowest two levels, PE and Light BPE, as required, to fulfil the purpose of the study.

This British Standard is relevant to all types and uses of buildings, at any point(s) during the “in-use” phase of their lives, including, but not limited to:

1)	a development of individual homes that has been recently constructed with homes sold to private individuals;
2)	a cohort of similar dwellings, pre- and post-upgrade to establish a baseline performance and then to verify improvements;
3)	a portfolio of public buildings to support a business case for investment; and
4)	a recently completed commercial building where the owner wishes to check that the specified performance has been achieved.

NOTE 2 “As built” performance of a newly constructed or upgraded building, prior to occupation might differ from the “in-use” performance once occupants have moved in. Completion stage (prior to occupation) studies are not covered by this British Standard.

NOTE 3 Evaluation in this British Standard is based on actual quantitative and qualitative data obtained through testing, measurement, monitoring, observations and reported experience.

NOTE 4 Actual data is compared against context-relevant reference cases (comparator cases) thus enabling the evaluator to report on individual and interdependent aspects of the performance of the building and thereby to draw conclusions pertinent to the objectives of the BPE project.

This British Standard specifies requirements for:

i)	the planning of BPE studies, including timing and content;
ii)	the choice of comparator cases;
iii)	data gathering relevant to the BPE project level, through documentation review, test and measurement, monitoring, experiential feedback and observations;
iv)	the derivation and reporting of gathered and derived performance parameter data;
v)	comparison of gathered data and derived performance data with equivalent comparator case data;
vi)	the interpretation of individual, interdependent and whole system results;
vii)	requirements for data naming and retention; and
viii)	reporting and compliance claims.

This British Standard does not include minimum or desirable values for directly obtained performance parameters (e.g. measured temperature) or for performance parameters derived from measured data (e.g. energy use per m²).

NOTE 5 Many sources are available that provide guidance on “what good looks like” and are updated on an irregular basis, including The Association for Environment Conscious Building (AECB) (https://aecb.net/) and Passive House (https://passivehouse-international.org/index.php) standards on energy intensity and water use; World Health Organisation (https://www.who.int/), BS EN 16798‑1 [B] and forthcoming BS 401022)guidance on indoor environmental conditions; relevant building regulations and CIBSE publications on air tightness and ventilation rates (https://www.cibse.org/). To provide assistance to the users of this British Standard, many of these sources are signposted where the evaluation of specific aspects of performance is addressed.

2 Normative references

3 Terms and definitions

4 Building performance evaluation methodology

4.1 Planning BPE projects

4.2 Conducting BPE projects

4.3 Data naming and retention

4.4 Interpretation and reporting

4.5 Evaluator responsibility and claiming conformity

5 Specification and execution of BPE elements

5.1 General

5.2 Preliminary Evaluation, Light BPE and Standard BPE

5.3 Occupant and user experience

5.4 Post-construction review

5.5 Energy use and generation

5.6 Water use

5.7 Internal condition monitoring

5.8 External condition monitoring

5.9 Investigative BPE

Bibliography

BS 40101:2022

Building performance evaluation of occupied and operational buildings (using data gathered from tests, measurements, observation and user experience). Specification

Current

Published:

31 Jan 2022