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CIBSE TM71: Measuring the Heat Transfer Coefficient of Buildings provides guidance on the measurement and application of building heat transfer coefficients. The HTC describes the overall rate at which heat is lost from a building and is a fundamental input to building energy calculations, heating system design, retrofit evaluation, and the assessment of building performance.
There is growing recognition that the thermal performance of buildings in practice can differ significantly from that predicted by design calculations. As a result, interest in measuring HTC directly has increased across industry, government, and academia. New measurement approaches have emerged that can provide evidence of building performance under both test conditions and normal operation, creating opportunities to improve the accuracy of building assessments and reduce uncertainty in decision making.
TM71 standardises terminology to enable comparability between the results of different test methods, and provides guidance on validation, uncertainty, reporting, and practical application. It is intended for professionals involved in the assessment, specification, regulation, construction, and retrofit of buildings, and aims to support the consistent and credible use of HTC measurements across the built environment sector
Acknowledgements: The CIBSE gratefully acknowledges support from Innovate UK. The Institution also wishes to thank Laura Forster (Innovate UK) for monitoring the development of this publication
Table of Contents
1 Introduction
1.1 Intended audience
1.2 What are heat transfer coefficients?
1.3 Why measure heat transfer coefficients?
1.4 The thermal performance gap
1.5 Aim of this TM within the standards and regulatory framework
2 Definitions and principles of heat transfer coefficients
2.1 Heat transfer coefficients
2.2 The building heat transfer coefficient
2.3 Building engineering physics of measuring heat transfer coefficients
2.4 Factors that can affect the measurement of heat transfer coefficients
2.5 Comparing building heat transfer coefficients
3 Overview of methods for measuring heat transfer coefficients in buildings
3.1 Quasi-steady-state measurement tests
3.2 Dynamic measurement tests
3.3 In-use measurements
4 Applying thermal performance measurement methods
4.1 Data collection
4.2 Sensors
4.3 Data analysis
4.4 Reporting
4.5 Quality assurance processes
5 Practical guidance
5.1 Choosing a suitable method for measuring the heat transfer coefficients of buildings
5.2 Potential applications of measured heat transfer coefficients
5.3 Further diagnostic testing
References and bibliography
Authors: David Allinson (School of Architecture, Building and Civil Engineering, Loughborough University) and Richard Jack (Build Test Solutions Ltd)
Steering committee: David Adams (Future Homes Hub), George Bennett (Department for Energy Security and Net Zero), Shona Cleland (Department for Energy Security and Net Zero), Kate Crawford (Knauf Energy Solutions), Hermione Crease (Purrmetrix), Tony Day (independent consultant), Cliff Elwell (UCL Energy Institute), David Glew (Leeds Sustainability Institute (LSI), Leeds Beckett University), Julie Godefroy (CIBSE), Kevin Gornall (Department for Energy Security and Net Zero), David Johnston (Leeds Sustainability Institute (LSI), Leeds Beckett University), Sarah Juricic (Centre Scientifique et Technique du Bâtiment), Kieron McGlinchey (Department for Energy Security and Net Zero), Johann Meulemans (Saint-Gobain), Bill Parker MBA, Chris Ricketts (Elmhurst Energy), David Ross (AECOM), David Shewan (Cotality UK), Bethany Taylor (City Science)
Peer reviewers: Richard Fitton (Energy House Labs, University of Salford), Chris Knights (BSRIA), Ellen Salazar (CIBSE)