Thermographic Surveys

A thermographic survey, also known as thermal imaging, uses a special infrared camera to see temperature differences across the surfaces of a building. This creates a “heat map” (or thermogram) that visually shows where a building is losing heat. It’s a non-invasive way to pinpoint problems like missing or defective insulation, air leakage pathways (draughts), cold bridging and even potential moisture issues.

To get accurate results, surveys need a temperature difference (ΔT) of at least 10°C between inside and outside, which is why they’re typically carried out during the colder months (November to April). Surveys also need to avoid solar loading, where the sun warms external walls and masks real thermal leaks.

Timing can get more complex on live sites: for The Marlowes Shopping Centre, which remained fully trading throughout, we ran the survey across two separate overnight sessions to eliminate solar loading and secure a reliable temperature differential.

Besides the 10°C temperature difference, several other conditions are required:

– The building should not have been in direct sunlight for at least 4 hours before the survey.

– There should be no rain or snow just before or during the survey, and the building’s surfaces must be dry.

– Wind speeds should be low (below 10m/s).

To ensure these conditions are met, surveys are often conducted in the early morning, late afternoon or at night.

For the clearest results, keep your heating running continuously for at least 2-4 hours before the survey, aiming for an indoor temperature of 20°C or higher. Keep all windows and external doors closed, and draw back curtains or clear anything blocking access to external walls.

Thermal imaging on its own reveals missing insulation and cold bridging, but pairing it with an air tightness test gives a genuinely complete diagnostic picture. Depressurising the building pulls cold outside air through gaps and structural cracks that wouldn’t otherwise be visible, making draught pathways show up clearly under the infrared camera.

By identifying exactly where energy is being wasted, a thermographic survey can change the whole direction of a decarbonisation plan – not just confirm it. At Horfield Health Centre, thermal imaging (combined with air tightness testing and a cavity wall inspection) revealed inconsistent insulation and leakage at the eaves, roofline, windows and doors. That evidence proved critical: modelling showed that installing an air source heat pump on the building as it stood would actually have increased running costs by around £6,000 a year, because the fabric was too poor for the heat pump to run efficiently. Fixing the fabric first, informed directly by the thermal imaging, was the only way the heating upgrade would ever pay off.

A basic thermal camera only shows surface temperature patterns, which can easily be misread due to reflection or other atmospheric variables. We use calibrated cameras and process every image through FLIR software to verify the underlying temperature data, then interpret it rather than handing it over as-is. At The Marlowes Shopping Centre, that interpretation work was the whole point: rather than treating every anomaly at face value, our thermographer filtered out transient effects to separate low-cost maintenance quick-wins (resealing door and window frames) from the capital works actually needed (insulation, thermal bridging) – giving a prioritised, actionable breakdown instead of a wall of colour with no context.

1. Improving Energy Efficiency – seeing exactly where heat is escaping lets you target specific areas for improvement, such as adding insulation or sealing draughts, reducing your energy bills.
Enhancing Comfort. Fixing the issues identified in a survey helps eliminate cold spots and draughts, creating a more stable, comfortable temperature all year round.

2. Early Problem Detection – the survey can catch issues like insulation faults or moisture ingress before they become major problems. During a thermographic survey at The Marlowes Shopping Centre, a cold patch on the roof above the management suite flagged a likely water ingress risk ahead of any visible internal damage, catching a moisture issue early enough to prevent more costly structural damage down the line.

3. Quality Assurance – if you’ve had insulation installed, a thermal survey can verify it was done correctly and is performing as it should.

4. BREEAM Compliance – for new builds and commercial projects, a BREEAM-compliant thermographic survey can help you achieve credits under the BREEAM sustainability assessment scheme. On the University of Bristol Veterinary School’s Blagdon Building, our thermal imaging found good continuity of insulation across the building’s external elevations and internal-to-external junctions, with no significant construction defects, directly supporting the project’s pursuit of a BREEAM thermographic credit.

Yes – thermography is entirely non-invasive, making it one of the safest diagnostic options for heritage, listed or otherwise sensitive structures where more invasive testing methods aren’t appropriate. For the Churches Conservation Trust’s St Paul’s Church, a Grade I listed Georgian building in Bristol, we used thermography alongside depressurisation air testing to trace air movement through the historic fabric – achieving the same visibility the original brief’s invasive smoke-testing method would have provided without any risk to the stone and timber.