Thermal image

About this image

© Historic England

Thermal Imaging

Infrared thermography is a non-destructive means of investigation capturing the heat energy emitted from the surface of a material.

Infrared cameras or thermal imaging cameras are used to capture radiation which is invisible to the human eye. The cameras convert the radiation into images. These images show variations in temperature from cold blues to hot reds and yellows.

There are multiple applications where infrared thermography may help with understanding and improvement of the performance of historic buildings:

  • Condition monitoring of heating and cooling systems
  • Identifying routes of heating and cooling systems
  • Leakage in pipework, pumps and valves, pipe blockages
  • Identifying condensation risk
  • Deterioration of fabric from damp or moisture ingress
  • Identifying physical characteristics and defects
  • Investigating electrical faults
  • Assessing energy efficiency improvements

A comprehensive survey of the building and the history of building services will be needed in order to interpret the infrared images.

Thermal image of the roof of The Engine House, Firefly Avenue, Swindon.
Thermal image of the roof: The Engine House, Firefly Avenue, Swindon. © Historic England / Caroline Cattini

Finding hidden historic heating systems

Thermal imaging has proved to be particularly useful in looking at heating systems that have been concealed so as not to detract from the interior design, or where building drawings with heating system layout, pipework routes and valves are not available. Hidden systems are difficult to maintain and problematic to fix if they leak or become blocked. Heating systems can also cause damage so it's useful to understand where pipes run.

image of the Drawing Room at Eltham Palace, London. Thermal image showing the historic heating coils in the ceiling
The Drawing Room at Eltham Palace, London. Thermal image showing the historic heating coils in the ceiling © Historic England / Caroline Cattini
image of Apsley House, Piccadilly, London. Thermal image showing the heating panels below the paintings
Apsley House, Piccadilly, London. Thermal image showing the heating panels below the paintings © Historic England / Caroline Cattini

Finding electrical faults

Electrical faults can generate excessive heat which can result in fires. Thermal imaging can be used to detect:

  • Hot spots from loose or over-tightened or corroded connections
  • Broken or under sized conductors
  • Defective insulation
  • Fuses near to their current capacity
  • Unbalanced loads

As part of the maintenance and testing of systems, thermal imaging should be used to check:

  • Switchgear
  • Busbars and associated connections
  • Cables and associated connections
  • Transformers
  • Motor control panels

The best results for thermal imaging electrical equipment will be obtained where the electrical equipment being inspected is under at least 40% of nominal load or ideally maximum load conditions. Panel covers and safety screens will need to be removed to expose the live terminals, busbars etc. As this involves ‘live working’ particular attention should be paid to safety and this work must comply with the Electricity at Work Regulations.

The results of the thermal imaging should be recorded and images kept as part of the Asset Register/Building Information Model (BIM):

BIM for Heritage

Published 20 July 2017

This publication raises awareness of the potential advantages of a BIM approach to help users successfully implement BIM in heritage projects.

Learn more

Other publications of interest

Soki Rhee-Duverne and Caroline Cattini (2018) Thermography in historic buildings Historic England Research Spring Issue 8 2018 volume8 pages.46-51

Historic England Research Issue 8

Published 6 April 2018

Keep up-to-date with projects and activities involving applied research into the historic environment.

Learn more
Was this page helpful?