"Making assumptions based on the scan alone is a common mistake," he says.

Thermography is the process of converting invisible infrared energy created by radiant heat into an image that can be seen and understood. Another definition: The process of using a really really expensive thermometer to map the relative temperature of a surface.

Scans with an infrared camera can show colder areas in darker colours and warmer areas in brighter colours. The warmer areas may indicate thermal bridges, variations in insulation levels, air exfiltration, or water leakage.

There are various factors that can dramatically affect the image you see.  For example; objects that are highly reflective are difficult to review because the heat energy from surrounding objects can be reflected at the camera, greatly altering the image. "Glass is tricky because it is very reflective but also transparent so the camera picks up objects radiating heat in front of and behind it," Hubbs explains. Thermographic scans should always be supported by other physical tests such as smoke testing, moisture probes, or exploratory openings depending on what you are looking for.

Thermography is an effective tool for determining if roof areas have been affected by water ingress in conventional roof assemblies. Sunshine heats up the roof during the day and after sunset, the dry insulation cools faster than the water saturated insulation.  A scan taken under these conditions will easily show areas affected by water. 

Because of the greater complexity and the the fact that all sides of a building cannot be uniformly heated by the sun like a roof, detection in walls is more difficult.  Rainscreen walls also incorporate cavities that separate the various layers of the walls from one another which lessens the heat flow and makes the effect less visible. Using thermographic scans to locate moisture in walls is not always effective.

Thermography is well-suited to detect air leakage in walls, particularly during the building commissioning process to help confirm that air and thermal barriers are continuous. To do this, two separate and complete scans of the building are required; the first at approximately 20+ Pascals of positive air pressure, and the second at  20+ Pascals of negative pressure. The scans must then be compared for inconsistencies in the 'hot spots.' The hot spots that occur in the positive scan but not the negative scan are often due to air leakage. Once identified, it is necessary to verify any suspected problems through physical testing such as a smoke tracer test.

Clearly identifying the purpose of your scan is the key to getting good results, says Hubbs. Different requirements will require unique investigation protocols.

"At its worst, thermography will lead you to incorrect information. At its best, it will dramatically decrease your time zeroing in on any real problem areas.”

Scan showing water within a roof assembly.

Scan showing water leakage within a wall assembly.