Step 1: Pre-Survey Environmental Recording

Before the thermal camera is even raised, a Level 3 thermographer will record and document the ambient conditions. This means logging the indoor air temperature, outdoor air temperature, and relative humidity using calibrated, traceable instruments. These measurements are time-stamped and form part of the formal survey record, because the dew point derived from them underpins every interpretation made from the thermal imagery.

We also assess whether conditions are stable enough for a valid survey. Thermography standards, including ISO 6781 and the guidance published by the Infrared Training Centre (ITC), specify minimum temperature differentials between inside and outside (typically at least 10°C) to create the heat flow necessary for meaningful thermal imaging of building fabric. Surveys conducted outside of these parameters risk producing misleading results, and we will advise clients accordingly rather than proceed with an inspection that cannot be properly interpreted.

Step 2: Real-Time Dew Point Calculation and Camera Setup

Once environmental conditions are confirmed as suitable, the calculated dew point is used to calibrate the analytical approach for the survey. Many professional radiometric thermal cameras allow the thermographer to input ambient temperature and humidity, enabling on-screen dew point margin overlays or alarms when surface temperatures approach the condensation threshold. More importantly, the experienced Level 3 thermographer holds this figure as a constant reference throughout the inspection, mentally and analytically comparing every measured surface temperature against the dew point.

Emissivity correction is also applied at this stage. Building materials have varying emissivities, which affect the accuracy of the apparent temperature reading. Incorrect emissivity settings can introduce temperature errors of several degrees, which could mean a surface appears to be above the dew point when it is in fact at or below it. Our survey methodology applies appropriate emissivity values for the materials being assessed, a task that requires both thermographic expertise and a working knowledge of construction materials.

Step 3: Identifying and Quantifying Condensation Risk Zones

During the thermal survey, areas where surface temperatures approach or fall below the calculated dew point are flagged as condensation risk zones. These typically manifest as cold thermal anomalies on internal surfaces, frequently corresponding to areas of thermal bridging (such as structural steel frames, concrete lintels, or uninsulated wall ties), areas of insulation failure or absence, air leakage pathways, or concealed moisture ingress. Each anomaly is documented with a radiometric thermal image, measured temperature data, and a written assessment of the condensation risk relative to the surveyed dew point.

A critical aspect of professional interpretation is distinguishing between areas that are merely cool and areas where the surface temperature is actually at or below the dew point. A poorly qualified or inexperienced thermographer may note a cold area without making this distinction, producing a report that creates concern without providing meaningful diagnostic information. At Level 3, our analysis provides clients with a quantified assessment of how far each anomaly is from the condensation threshold, a figure that carries direct design and remediation implications.

Step 4: Reporting with Scientific Defensibility

Our thermography reports are structured to a professional standard, with all environmental data recorded, emissivity assumptions stated, and thermal images presented alongside their visible-light equivalents for accurate context. Each condensation risk finding is referenced to the calculated dew point and given a risk classification that reflects the magnitude of the temperature differential between the measured surface and the dew point threshold. Where surface temperatures are within 2°C to 3°C of the dew point, we classify these as elevated risk zones requiring monitoring or investigation. Where surface temperatures are at or below the dew point, we classify these as active condensation sites requiring immediate remediation consideration.

This scientific framing makes our reports directly usable by architects, building surveyors, engineers, and contractors who need defensible evidence to support design decisions, remediation scoping, or insurance or legal proceedings. We also offer a standalone Level 3 report writing service for thermographers at Levels 1 and 2 who require an independent, higher-qualification review of their thermal data, details of which can be found on our Report Writing Services page.

Mould colonisation in buildings is fundamentally a moisture problem. Mould spores are ubiquitous in the environment and will germinate and grow wherever the moisture content of a surface or material remains above a critical threshold for a sustained period. The moisture that feeds mould growth is frequently the product of condensation at or near surfaces that are persistently below the dew point, and this is where dew point analysis in thermography becomes a direct mould risk assessment tool.

When a surface temperature falls below the dew point, moisture begins to accumulate. Over time, particularly in areas of restricted air movement such as behind furniture placed against external walls, within reveals, or in poorly ventilated roof voids, this accumulated moisture creates conditions in which common building moulds, including Cladosporium, Penicillium, and Aspergillus species, can establish and thrive. These organisms not only cause cosmetic damage but produce volatile organic compounds and allergens that can significantly affect indoor air quality and the health of building occupants.

A thermography survey that correctly identifies and quantifies the condensation risk at surfaces, grounded in accurate dew point analysis, provides building owners, facilities managers, and housing providers with objective evidence of where mould risk is highest. This evidence can be used to prioritise remediation, direct ventilation improvements, and support the case for insulation upgrades or thermal bridge mitigation works. It also provides a pre-remediation baseline against which post-remediation thermography can demonstrate that improvements have been effective.

One of the less-discussed but critically important aspects of building thermography is the fact that survey results are only valid within specific environmental conditions. This is not merely good practice guidance; it is a scientific necessity rooted in the physics of heat transfer and the limitations of infrared measurement. A survey carried out in inappropriate conditions will yield thermal images that cannot be reliably interpreted, however sophisticated the camera equipment used.

For dew point analysis to be meaningful, the relative humidity indoors needs to be representative of habitual occupancy conditions. Surveys carried out in vacant properties with low humidity and low occupancy loads will record a dew point that does not reflect the condensation risk experienced during normal use. Conversely, surveys following recent heavy rain, cooking, drying of laundry, or bathing without ventilation may record temporarily elevated humidity that inflates the apparent condensation risk. Our survey protocols include an occupant questionnaire or facilities management briefing to understand the typical indoor environment before survey conditions are assessed as representative.

It is also important that the survey is conducted during a period of thermally stable conditions, ideally following at least 24 hours without significant solar gain on the facades being assessed. Solar loading heats wall surfaces from the outside, which temporarily masks cold bridges and moisture anomalies on internal surveys. We schedule surveys with these constraints in mind, and our survey reports always state the conditions under which the inspection was carried out so that the limitations and scope of the data are fully transparent.

How common survey conditions affect the validity of dew point analysis in building thermography.

Residential and Commercial Properties with Recurring Dampness Complaints

Where tenants, occupants, or building managers are experiencing recurring damp or mould issues and conventional visual inspection has not identified a clear cause, thermography with dew point analysis can provide the diagnostic clarity needed. By identifying the specific locations where surface temperatures fall below the dew point under typical occupancy conditions, the survey delivers objective evidence to distinguish between condensation caused by thermal bridge defects, insulation failures, or occupant behaviour, a distinction that has significant implications for remediation responsibility and approach.

Energy Performance and Building Fabric Assessment

In the context of energy performance assessments, SAP calculations, and EPC uplift strategies, a thermography survey incorporating dew point analysis reveals not just where heat is being lost, but where that heat loss creates a secondary risk through condensation and moisture accumulation. Thermal bridges that lower surface temperatures to near-dew-point conditions increase both heat loss and moisture risk simultaneously, and addressing them delivers benefits both in terms of energy efficiency and occupant health. Our reports can be used to support improvement planning and to provide evidence of compliance with building regulations Part L and Part C requirements.

Pre-Purchase and Pre-Lease Surveys

Building professionals, investors, and prospective tenants commissioning a thermography survey before purchase or lease are specifically interested in understanding the latent moisture and condensation risks within the building fabric. A Level 3 survey with dew point analysis goes beyond what a standard surveyor’s visual inspection can detect, identifying hidden cold bridges, concealed moisture ingress, and insulation defects that would not be visible to the naked eye. This intelligence can inform negotiation on price or condition precedents, and can identify risks that would otherwise only become apparent once occupation begins.

Post-Remediation Verification

Following insulation upgrades, external wall insulation installation, internal dry-lining, or other fabric improvement works, a thermography survey with dew point analysis provides objective evidence that the remediation has been effective. By demonstrating that previously below-dew-point surface temperatures have been raised above the condensation threshold under equivalent environmental conditions, the survey provides a scientifically defensible confirmation of improvement, useful both for warranty purposes and for ongoing maintenance planning.