Thermal only works when conditions do
A thermal camera shows surface temperature, not water or insulation. Flown at the right time, it points a consultant to wet roof insulation, missing insulation and air leaks. Flown at the wrong time, it shows noise.
Surface temperature, and what makes it tell a story
An infrared camera measures the heat radiating from a surface and turns it into an image. A radiometric camera stores a temperature value for every pixel, so a thermographer can analyse the file later: adjust the range, measure spot temperatures, correct for emissivity and distance, and compare areas. A non-radiometric camera only gives you a coloured picture. For inspection, we fly radiometric sensors and deliver the radiometric files, not just the coloured JPEGs.
Thermal does not see through walls or roofs. It sees how heat moves to the surface. Wet insulation holds heat longer than dry insulation. A wall with a gap in the insulation loses more heat on a cold night. Air leaking out of a building warms the cladding around the leak. The camera sees the effect, and a trained person works out the cause. That makes thermal a natural partner to a visual roof inspection or a building envelope survey.
That is why conditions are everything. Without a temperature difference driving heat through the assembly, there is no pattern to see. With sun on the surface, the pattern is swamped by solar heating. With wind, surfaces cool evenly and the pattern fades. With a wet surface, evaporation cools everything and hides what is underneath.
What each type of thermal survey needs
| Survey | Temperature difference | Time of day | Wind and moisture |
|---|---|---|---|
| Roof moisture (low-slope membrane roofs) | Built up by the roof absorbing heat during a sunny day; wet areas release it more slowly after sunset | After sunset on a clear evening following a sunny day, before surfaces reach equilibrium | Low wind; roof surface dry, free of ponding, snow and debris; no significant rain in the day or so before |
| Heat loss and insulation (walls and roofs) | A sustained inside-outside difference, commonly around 10 °C or more for several hours | Night or early morning, with no direct sun on the surfaces for several hours before | Low wind; dry surfaces; HVAC state known and steady |
| Air leakage | Inside-outside temperature difference plus a pressure difference, sometimes created with a blower door | Heating season, night or early morning | Low wind; coordination with the building operator |
| Solar panels | Created by the panels operating under strong sunlight | Middle of a clear day | Low wind; see solar inspection |
Methods your consultant will recognise
Roof moisture surveys are commonly done to ASTM C1153, the standard practice for locating wet insulation in roofing systems using infrared imaging. It calls for suitable weather, a dry roof surface, and verification: thermal anomalies are marked and then confirmed with core samples or moisture readings, because thermal alone is not proof of water. Building envelope work often references ASTM C1060 for insulation in frame buildings, and ISO and Canadian standards cover thermographic qualification of envelopes. Thermographers are typically certified in levels, with higher levels signing interpretation.
We capture to the method your thermographer or roofing consultant specifies, and we tell you plainly when forecast conditions will not meet it. Flying anyway only gives you a file that nobody should rely on.
A roof moisture survey, step by step
Confirm the roof type
Thermal moisture surveys work best on low-slope membrane roofs with absorbent insulation. Steep-slope roofs, ballasted roofs and some insulation types give weaker or misleading results.
Watch the forecast
We look for a dry, sunny day followed by a clear, calm evening, and hold a backup date.
Plan the night flight
Flights after sunset need the aircraft lit for night operations and a site survey done in daylight. In controlled airspace, authorization is arranged ahead. In the US, Part 107 night rules apply. See Canadian drone rules and US drone rules.
Fly and capture
A mapping grid of the whole roof in thermal, plus a daylight visual set for reference, so every anomaly can be placed on a map.
Mark anomalies
The thermographer outlines suspected wet areas on the thermal orthomosaic.
Verify on the roof
The roofing consultant takes cores or moisture readings at marked areas to confirm. Only then does the repair scope get written.
Why thermal surveys disappoint
Reflections read as hot spots
Metal flashing, glass and wet membranes reflect sky and surroundings, so the camera reads the reflection, not the surface.
A daytime flight for a heat loss job
Sun-loaded walls show the sun, not the insulation.
Coloured pictures with no data
A report full of rainbow images that cannot be re-analysed.
Questions
Can a drone thermal camera find roof leaks?
It finds areas where insulation under the membrane is likely wet, which is usually where water has entered. Those areas are then confirmed with cores or moisture readings before any repair is planned.
What is the best time of day for a thermal roof inspection?
For roof moisture, after sunset on a clear, calm evening that follows a sunny day, while the roof is releasing the heat it absorbed. For heat loss from a building, at night or early morning in the heating season.
How much temperature difference do you need for thermal imaging of a building?
A sustained difference between inside and outside is needed. Around 10 °C or more held for several hours is a commonly used guide, but your thermographer's method sets the actual requirement.
What is radiometric thermal imaging?
Every pixel carries a temperature value that can be analysed after the flight. Non-radiometric images are just pictures, which makes them much less useful as evidence.
Can thermal imaging see through walls?
No. It sees surface temperature. Patterns on the surface can suggest missing insulation, moisture or air leaks behind it, which a trained thermographer interprets.
Can drones fly thermal inspections at night in Canada?
Yes, when the pilot and aircraft meet the night operation requirements and the site survey and any airspace authorization are in place. The US allows night flights under Part 107 with lighting and training requirements. Check the current rules.
What drives the cost of a drone thermal survey?
Roof or building size, night work, waiting for suitable weather, the level of thermographer reporting, and whether verification cores are part of the scope.
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