CIBSE has published its new Technical Memorandum, CIBSE TM71: Measuring heat transfer coefficients in buildings, developed with support from Innovate UK.
The guidance sets out a clear framework for understanding, measuring and interpreting Heat Transfer Coefficients (HTC) in buildings, supporting a growing shift towards evidence-based assessment of real-world building performance.
Led by Professor David Allinson from Loughborough University and Dr Richard Jack from Build Test Solutions and an independent steering group, the Technical Memorandum brings together definitions, data requirements and practical recommendations for measurement and interpretation.
It is intended to strengthen the industry’s ability to move beyond theoretical assumptions towards measurable, verifiable performance outcomes.
Supporting better understanding of real performance
Heat Transfer Coefficients are widely used in building design and assessment, particularly for sizing heating systems, planning retrofit interventions and informing energy models. However, these values are typically calculated rather than measured.
While for a long time the main method available was co-heating tests, a number of other approaches have been developed in recent years. The new guidance describes the methods available, helping users choose the most appropriate for their context, standardises reporting, ensures comparability between the results of different methods, and highlights how in-situ measurement of HTC can provide a more accurate understanding of actual building performance. It also explains how measured values can be used alongside or in place of calculated values to improve decision-making.
Comparing calculated and measured HTC values can also help identify gaps in design assumptions, construction quality or modelling inputs, offering a valuable check on building performance and delivery quality.
Broad relevance across the built environment
The Technical Memorandum is aimed at a wide range of professionals involved in the design, assessment, construction, regulation and retrofit of buildings.
This includes specialists involved in building thermal performance measurement and commissioning, particularly providers of in-situ HTC testing services. While HTC measurement has traditionally been focused on domestic buildings, the guidance confirms its relevance and applicability to non-domestic buildings as well.
It is also intended to support regulatory and oversight bodies, including government departments, standards agencies, accreditation schemes and local authorities with responsibilities for housing, retrofit and planning.
In addition, the guidance will be relevant to developers, landlords, consultants and contractors involved in specifying, delivering and evaluating building performance outcomes.
A step towards performance-led practice
By formalising approaches to measuring and interpreting heat transfer coefficients, the Technical Memorandum supports a broader industry shift towards improved accountability and performance verification in buildings.
It reinforces the importance of robust data, consistent methodologies and clearer links between design intent and operational reality.
You can find and download CIBSE TM71: Measuring heat transfer coefficients in buildings HERE