Thermal imaging in building inspections

A thermal camera shows differences in surface temperature. In a building inspection, those differences can point to missing insulation, air leaks, hidden moisture, overheating electrical parts and failing mechanical equipment. It does not see through walls, and it does not show moisture or mould directly, so its findings need to be confirmed with other tools and a trained eye.

How thermal imaging works

Every surface gives off infrared radiation, and warmer surfaces give off more. A thermal camera measures this radiation and turns it into an image, with colours representing temperature. The camera reads only the surface it is pointed at. What is happening inside a wall shows up only if it changes the temperature of the surface.

Several factors affect the reading:

• Emissivity. Shiny surfaces such as bare metal and glass reflect heat from other objects, so their apparent temperature can be misleading.
• Reflections. A warm person or light fixture can reflect off a surface and look like a hot spot.
• Temperature difference. Building envelope scans need a meaningful difference between inside and outside. In Canada, cold-weather scans with the building heated generally give the clearest results.
• Sun and wind. Sunlight warming a wall, or wind cooling it, can mask or create patterns.

What it can find

Building envelope

• Missing, settled or wet insulation in walls and ceilings.
• Air leaks around windows, doors, outlets and top plates, especially when combined with a blower door test. See air leakage around windows and doors.
• Thermal bridging through framing, slab edges and balconies.
• Heat loss into attics that can lead to ice dams.

Moisture

Wet materials often show up cooler than dry ones because evaporation cools them. A thermal image can suggest where water from a leak has spread in a ceiling or wall. A moisture meter is then used to confirm whether the area is actually wet. Flat roofs can also be scanned, usually in the evening, to find wet insulation under the membrane. Moisture leads to mould, covered in moisture, mould and indoor air.

Electrical systems

Loose connections, overloaded circuits and failing components often run hot before they fail. Infrared scanning of electrical panels and switchgear under load is a well-established maintenance practice. It requires a qualified person and appropriate arc flash precautions when covers are removed. See infrared thermography for electrical systems.

Mechanical systems

• Radiant heating loops and hot water piping.
• Blocked or unbalanced radiators and coils.
• Overheating bearings and motors.
• Leaking ducts and steam traps.

What it cannot do

• It cannot see through walls, glass or metal. Glass is effectively opaque to most building thermal cameras.
• It cannot detect mould, asbestos, or structural damage directly.
• It cannot prove a material is wet. Cool areas can also come from air leaks or missing insulation.
• It does not replace opening up an area when a confirmed problem needs to be repaired.

Getting useful results

1. Plan for conditions. For envelope work, aim for a good temperature difference between inside and outside, avoid direct sun on the surfaces being scanned, and avoid high wind or rain.
2. Prepare the building. Keep heating running normally, move furniture away from exterior walls where possible, and close windows and doors.
3. Load electrical and mechanical systems. Equipment should be operating under normal load when scanned, since problems often only show under load.
4. Combine tools. Use moisture meters, blower door testing or electrical testing to confirm what the camera suggests.
5. Document properly. Each thermal image should be paired with a normal photo, location and conditions, so repairs can be targeted.

Reading an image: a worked example

A typical case: during a winter inspection of a small office building, the thermal camera shows a cool, irregular area on a ceiling near an exterior wall on the top floor. On its own, that image could mean several things. The inspector works through them:

1. Check the conditions. Is the building heated normally, is there a good temperature difference to outside, and has the sun been on the roof? Record indoor and outdoor temperatures with the image.
2. Look at the shape. A sharp-edged rectangle between framing often means missing insulation. A narrow streak spreading from a joint or a corner suggests air leakage. An irregular blotch with soft edges, sometimes lower in the middle, often points to moisture.
3. Rule out reflections. Move and view the surface from a different angle. A reflection moves with the camera; a real temperature pattern does not.
4. Confirm with another tool. Here, a moisture meter shows elevated readings in the middle of the cool area and normal readings around it. That points to water, not just missing insulation.
5. Trace the source. The roof above is checked, and a blocked roof drain with ponding water is found near that location.
6. Record it. The thermal image, a matching normal photo, moisture readings and the location are recorded together so the repair can be targeted and checked afterwards.

What a thermal imaging report should include

• The date, time, indoor and outdoor temperatures, wind and sun conditions during the scan.
• The camera used and the settings that affect readings, such as emissivity.
• Each thermal image paired with a normal photo and a clear location.
• An interpretation of each finding, and how it was confirmed.
• Areas that could not be scanned or where conditions limited the results.
• Recommended follow-up, such as moisture testing, opening up or repairs.

How ehZee can help

ehZee uses thermal imaging as one tool within broader inspections, alongside moisture readings and a hands-on review of building systems. Our commercial building inspections combine these findings into a report that explains what was found and what to do about it.

Common questions