Thermal drones find roof leaks by spotting wet insulation, which holds the sun's heat longer than dry insulation and shows up warmer on a thermal image after sunset. The best time to fly a moisture survey is in the evening after a clear, sunny day, with a dry roof surface and light wind. Thermal shows where to look; a roofer confirms moisture with core samples or a moisture meter before repairs.
How thermal leak detection works
During the day, the sun heats the roof. Wet insulation has more thermal mass than dry insulation, so after sunset it cools more slowly. In a thermal image, wet areas appear as warmer patches with irregular edges, often near drains, seams, curbs and penetrations. This works best on low-slope commercial roofs with insulation under a membrane (built-up, modified bitumen, single-ply).
Conditions that matter
- A sunny day before the flight to load heat into the roof.
- Fly after sunset once the surface has started to cool, before dew forms.
- Dry surface. Standing water, dew or frost hides results.
- Light wind. Wind cools the surface evenly and erases the contrast.
- Avoid reflective surfaces. Shiny metal and some coatings reflect the sky and give false readings.
Heat-loss scans
To find missing insulation and air leaks, fly on a cold night when the building is heated. Warm streaks and patches on the roof show where heat escapes. This is common for homes and older buildings.
Running the flight
- Check airspace and get LAANC if needed; night flying under Part 107 requires current training and anti-collision lights visible for 3 statute miles.
- Fly a visual pass in daylight first to map drains, equipment and penetrations.
- After sunset, fly the roof in overlapping passes with the thermal camera pointed close to straight down.
- Capture visual and thermal images together so each anomaly has a reference.
- Mark suspect areas on a roof plan for core sampling.
Which drone to use
| Drone | Thermal | Notes |
|---|---|---|
| Matrice 4T | 640 x 512 (1280 x 1024 with Super Resolution) | Radiometric, wide plus two telephotos |
| Matrice 30T | 640 x 512 | IP55 for damp evenings |
| Matrice 350 RTK + Zenmuse H30T | 1280 x 1024 | Large commercial and industrial roofs |
The Mavic 3 Enterprise 3T (640 x 512) is a compact, lower-cost option. See best thermal drone.
Training and reports
Reading thermal images takes training. Reflections, different materials and HVAC equipment can all mimic moisture. A thermography course is worth it before you sell this service. Deliver a roof plan with marked anomalies, thermal and visual images side by side, and recommended core locations. See drone inspection reports.
Rules
Paid inspections need Part 107. Night flights follow Part 107's night rules.
Rules current as of October 2026. This is general information, not legal advice.
Starting with visual roofs first? Read how to do a drone roof inspection.
Related guides
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