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.
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.
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:
- Busbars and associated connections
- Cables and associated connections
- 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
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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
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