What Does Thermal Imaging Detect on Buildings? Water, Insulation and Debonded Finishes
Updated 13 October 2026 · SG Drone Inspections
Thermal imaging, or infrared thermography, shows the surface temperature of a building as an image. Many building defects change how a surface heats up or cools down, so they show up as warmer or cooler patches. Used properly, thermal imaging helps locate water ingress, debonded finishes, missing insulation and air leakage without opening up walls or roofs. Used without care, it produces misleading pictures. This guide explains both.
How Thermal Imaging Works
Every surface gives off infrared radiation in proportion to its temperature. A thermal camera measures this radiation and converts it into an image in which each pixel represents a temperature. A radiometric camera records the actual temperature value of each pixel, so it can be analysed later. A non-radiometric camera only produces a picture.
A defect only shows up if it creates a temperature difference at the surface. That depends on heat flowing through the material, whether from the sun, from air-conditioned interiors or from evaporation, so timing and weather are critical.
What It Can Detect
| Defect | How it appears | Best conditions |
|---|---|---|
| Debonded tiles and render | The air gap behind a detached finish insulates it, so it heats faster in sun (warmer) and cools faster at night (cooler) | Strong, steady sunshine on the elevation; or the evening cool-down |
| Water ingress in walls | Wet areas are often cooler because of evaporation, with irregular, spreading shapes | Dry weather after the wall has had a chance to show drying patterns |
| Wet roof insulation | Wet insulation holds heat, so it stays warmer than dry areas after sunset | Clear, dry day with good sun, surveyed in the evening |
| Missing or damaged insulation | Patches where heat flows more easily; in air-conditioned buildings these appear cooler from outside | A steady temperature difference between inside and outside |
| Air leakage | Streaks or plumes of conditioned air escaping around openings, joints and frames | Building operating normally with air-conditioning running |
| Solar panel faults | Hot cells, strings or connections compared with neighbouring panels | Panels under load in strong sunlight |
| Electrical hot spots | Overheating connections, breakers or cables | Equipment running under normal load |
What It Cannot Do
- It does not see through walls. It shows surface temperature only. A cool patch could be moisture, a shadow, a different material or a pipe behind the wall.
- Glass and polished metal mislead. These surfaces reflect infrared like a mirror, so the image shows reflected sky or surrounding buildings rather than the surface itself. Thermal surveys of curtain walls need particular care.
- Weather can hide defects. Rain, wind, cloud and shade all reduce or distort temperature differences. A survey on the wrong day may find nothing.
- Findings need confirming. Suspected defects should be checked with another method, such as tap testing for debonding or a moisture meter for damp, before repairs are specified.
Finding Water Leaks
Leaks are one of the most common reasons for a thermal survey. Water moves inside walls and roofs before it appears indoors, so the stain on a ceiling is often some distance from the point of entry. Thermal imaging can trace the wet area back towards its source by showing the extent of damp material.
On flat roofs, a survey after a sunny day can show where water has entered the insulation beneath the waterproofing membrane, because the wet areas stay warm after sunset. This can narrow repairs to the affected area instead of replacing the whole roof covering, though core samples are normally taken to confirm the findings.
Insulation, Heat Gain and Energy Audits
In Singapore the main energy concern is heat getting in, not heat escaping. In air-conditioned buildings, missing insulation, thermal bridges (such as concrete beams or metal fixings running through the insulation) and air leaks around windows and doors all increase cooling load. Thermal imaging makes these visible and is often used alongside energy audits to locate where the building envelope is underperforming.
Cold rooms and cold stores are particularly suited to thermal surveys, because the large temperature difference makes insulation defects and door-seal leaks easy to see.
Thermal Imaging From Drones
Mounting a thermal camera on a drone allows a whole facade or roof to be surveyed quickly, including areas that are hard to reach. The same physics and limitations apply, with a few extra considerations:
- Viewing angle matters: surfaces viewed at a steep angle reflect more and emit less, so flight paths are planned to look at surfaces as directly as possible.
- Thermal cameras have lower resolution than visual cameras, so they are flown closer or used with a visual camera to locate defects precisely.
- Flight timing is planned around solar loading for each elevation, which can mean surveying different sides of a building at different times of day.
Relevant Standards
Infrared thermography of buildings is covered by several international standards, which are useful references when specifying or reviewing a survey:
- ISO 6781-1 — detection of heat, air and moisture irregularities in buildings by infrared methods.
- ASTM C1153 — location of wet insulation in roofing systems using infrared imaging.
- ASTM D4788 — detecting delaminations in concrete bridge decks using infrared thermography, a method also referenced for other concrete surfaces.
Frequently Asked Questions
Sources and Further Reading
This article is general information, not legal or engineering advice. Regulations change; check the current requirements with BCA or a Competent Person before acting.