Infrared cameras add new dimension to moisture detection
Moisture damage in residential and commercial buildings can lead to very costly repairs for builders and contractors. Whether the root of the problem is storm damage, or run-of-the-mill plumbing or roof leaks, the key to avoiding ongoing problems is identifying and locating moisture problems before they escalate.
Visual inspections can only provide limited information. In some cases, the process can require intrusive measures – such as removing drywall or tiles – to detect the source of moisture within walls or ceilings.
Moisture meters are helpful, but it takes time to examine a site since it requires an inch-by-inch search. Within the last few years however, infrared cameras (also called thermal imagers) have become increasingly useful complementary tools for locating moisture problems in buildings. Unlike moisture meters, infrared cameras have the ability to scan an entire room in a matter of minutes to locate any thermal changes from evaporative moisture cooling (EMC) in drywall, carpet, ceiling tiles, etc. The speed and accuracy of the device allows inspectors to quickly moisture map an entire building and isolate problems before establishing the cost of repairs.
How it works
Unlike a moisture meter, an infrared camera doesn’t actually “see” moisture. Rather, it detects the temperature differential caused by moisture on a given surface, which creates unique thermal patterns. A thermal imager can show the presence of water below a surface because of properties such as heat capacitance, which is the normal method of choice when looking for failures in flat or low slope roofs.
The evaporative cooling effect is usually the most powerful indicator when moisture gets into studs, insulation and other interior wall components. It cools the surface of the material and creates a low-temperature thermal anomaly when compared to the surrounding dry materials. This evaporation effect applies primarily to interior inspections where the temperature and other elements are controlled. Exceptions include certain types of roof systems, where wet material in the ceiling creates a warmer thermal pattern as the sun heats water trapped in the roof materials.
An infrared camera is capable of detecting trapped moisture beneath multiple layers of materials. It can also be used even when the surface is covered with paint, flooring or certain other finishes.
Tips for accurate measurements
As with any inspection technology, there is a right way and a wrong way to go about using it. Although building interiors are usually controlled environments, inspectors must still take into account several factors to ensure they get accurate measurements. These include:
- Air temperature – Ambient cold or warm air can create both false positives and false negatives. For example, warm supply air can mask wet materials by warming the surface enough to distort or negate the thermal pattern created by evaporation. In comparison, the cold air from an air conditioning supply can create a thermal pattern similar to that of a moisture problem to generate a false positive reading.
Drying equipment used inside a structure during a water loss creates an enormous amount of heat. When in use, numerous air movers direct high volume, high-pressure warm air to the wet surfaces, increasing the chance of a false negative. In these cases, the warm air from the air movers can mask the cooler thermal pattern created by EMC, giving the user the impression the material is dry. And although the ambient air alone does not adversely affect the thermal pattern of wet to dry, the placement of the drying equipment can have an impact on readings.
- Insulation – Thermal patterns can be masked by missing or compressed wall insulation, also creating both false positives and false negatives. On the one hand, missing/compressed wall insulation on a warm, sunny day can cause the materials and moisture inside a wall cavity to heat up to a point where the thermal pattern becomes negated or distorted. In comparison, on a cold day, the same missing/compressed wall insulation can create a cooler thermal pattern that is similar to that of wet materials. In both situations, it is important to use a moisture meter to verify the presence of moisture.
- Ceramic tile – Most interior building materials have high emissive values, making them perfect candidates for thermal imaging. However it can be difficult to detect moisture beneath ceramic tile and certain other floor and wall coverings. Because the moisture in most cases is actually in the sub-floor and not in the floor covering itself, the temperature changes in the web sub-floor may not transfer through to the surface of the floor covering. Unwanted reflections can make matters even worse by distorting the true thermal pattern.
- Windows, siding, and exteriors – When inspecting for exterior moisture infiltration from windows, siding or other exterior components, it can take an hour or longer after wetting for a thermal pattern to become apparent on the interior. By way of example, let’s say a point of intrusion was believed to be above a living room window. The exterior wall was soaked with a sprayer per the ASTM standard. After 20 minutes there was no sign of water intrusion on the interior wall or floor. The wall was soaked again for an additional 10 minutes and still there was no thermal pattern evident. It wasn’t until nearly an hour after the initial spray test that the thermal pattern from the wet stucco and insulation was visible. Although the moisture penetrated the stucco within minutes after the first spray test, it took almost an hour for the cooler evaporative temperatures to reach the surface of the interior wall.
The financial impact of undetected moisture problems in buildings continues to escalate. Despite the fact that moisture meters play a valuable role in providing final confirmation of wet and dry materials, there is an ongoing need to find more effective and efficient ways to locate moisture in buildings accurately and efficiently. With infrared technology, building inspectors, contractors, and remediators can reduce liability and inspection time, while reducing overall costs. When used with the right tools in the right situation, an infrared camera is a very powerful and useful piece of inspection equipment.
Colin Plastow is Industrial Product Manager for Fluke Canada, with an expertise in electronic test and measurements. Mr. Plastow shares his industry knowledge through various customer seminars, as well as educational articles. He may be contacted at firstname.lastname@example.org