A thermographic survey is only as reliable as the conditions it’s carried out in. Get the timing, temperature or weather wrong and the result isn’t just less accurate – it can be inconclusive altogether, meaning a retest, a schedule delay and an added cost that a bit of upfront planning would have avoided. Below are the specific conditions we work to, along with what’s assumed, included and excluded as standard.
In this blog you’ll learn:
- Why getting these conditions right matters for the result
- The recommended temperature, weather and lighting conditions for an accurate survey
- What’s assumed, included and excluded as standard
Recommended Conditions for a Thermographic Survey
To achieve a reliable result from a thermographic survey, the following conditions need to be met:
- Stable ambient air temperature – within ±10ºC for the 24 hours preceding the survey (12 hours for lightweight fabric).
- A minimum temperature difference – at least 10ºC between internal and external temperatures, sustained for at least 24 hours before the test.
- No direct solar radiation – inspected surfaces should be free from direct sunlight for at least 4 hours before the survey starts, longer where the building has significant thermal mass, such as solid brick walls.
- Stable conditions during the survey – ambient air temperature within ±3ºC for the survey itself and the hour preceding it.
- Dry conditions – no precipitation just before or during the survey, and all surfaces to be inspected must be dry.
- Low wind speeds – below 10m/s, to avoid inaccurate readings.
Assumptions, Inclusions & Exclusions
- Timing: surveys are typically conducted in the afternoon or at night, to reduce interference from solar gain.
- Access: full internal and external access is required for the areas being surveyed.
- Insulation standards: continuity-of-insulation surveys meet the requirements of BRE report 176 and BS EN 13187:1999.
- Roof inspections: only sections of roof visible from the ground or a suitable adjacent building are included as standard. Specialist access equipment, such as a lift, carries an additional charge.
- Retesting: any retest required for a defective area is charged separately.
Our Expert Insight: Why These Conditions Matter
Our technical team treats these conditions as a genuine pass/fail gate, not a formality. A survey run outside the recommended temperature differential or into direct sunlight can produce a thermogram that looks plausible but doesn’t actually reflect the building’s real performance – the risk isn’t just a wasted visit, it’s a result you can’t confidently act on. That’s why we check forecast and site conditions against this list before every booking, rather than working it out after the fact.
Working Within Real Building Constraints
Meeting these conditions isn’t always straightforward on an occupied or actively-used building. At St Paul’s Church, we coordinated early-morning mobilisations around Circomedia’s use of the building, capturing thermography and air tightness data without disrupting its daily use – a reminder that these conditions have to be planned around the building’s real schedule, not just the weather.
What’s Next?
Meeting the right conditions is what turns a thermographic survey into evidence you can actually rely on, rather than a set of images that look informative but don’t hold up to scrutiny.
If you’re planning a survey and want to check timing or site conditions in advance, get in touch and we’ll talk it through.
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