CIBSE has published new guidance setting out a clear framework for understanding, measuring and interpreting heat transfer coefficients (HTC) in buildings.
The new technical memorandum, CIBSE TM71: Measuring heat transfer coefficients in buildings, was developed with support from Innovate UK, and supports a growing shift towards evidence-based assessment of real-world building performance.
The guidance 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 and towards measurable, verifiable performance outcomes.
HTCs are widely used in building design and assessment, particularly for sizing heating systems, planning retrofit interventions and informing energy models. However, they are typically calculated rather than measured.
For a long time, the main method available was co-heating tests, but 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.
In addition, comparing calculated and measured HTC values can help identify gaps in design assumptions, construction quality or modelling inputs, offering a valuable check on building performance and delivery quality.
By formalising approaches to measuring and interpreting HTCs, the publication supports a broader industry shift towards improved accountability and building performance verification.
CIBSE TM71 is available at: www.cibse.org/knowledge