Thermal Imaging
Understanding Building Infrared Imagery
Infrared imagery is often a grayscale picture or thermogram whose scales (or shades of color) represent the differences in emitted energy from the surface, often referred to as temperature. As a general rule, patterns in the image that are lighter in shade represent warmer temperatures; darker patterns represent cooler temperatures. Unlike visible imagery that captures visible light in the 0.4-0.7 micrometer wavelengths, objects observed using infrared imagery capture infrared wavelengths in the 8-14 micrometer range.
Qualitative Infrared Thermographic Survey
Areas that indicate faults often appear warmer due to increased load or possible arcing. Depending on conditions at the time of the inspection, such as sun exposure, wind, relative humidity, and temperature, those typically warmer patterns may be elevated in risk or potentially masked due to artifacts. Infrared imagers can detect this heat and “see” the warmer or cooler patterns, allowing the thermographer with proper training and additional tools to interpret those patterns correctly.
Qualitative Infrared Thermographic Survey Of HVAC System
An HVAC system is tested with a basic temperature differential between supply and return ducts to assess the basic cooling or heating efficiency of the system. This is not a complete, detailed review, but rather a simple test to help understand if the system is performing with acceptable tolerances. If an advanced duct location test was performed within the building over a series of locations, this test would help identify areas of increased or decreased cooling, which often can be contributed to improperly sized ducts or duct leakage. Although it is not an exact science, some minimal variances between locations are normal. However, higher temperatures have been found to be a result of deficiencies within the system. Often it will be necessary to have additional testing to confirm the conditions that may be the cause of the findings. Depending on the conditions at the time of the inspection, direct sun exposure, wind, relative humidity, and temperature may impact the findings. Infrared imagers can detect and “see” the warmer or cooler patterns, allowing the thermographer with proper training and additional tools to interpret those patterns correctly.
Qualitative Infrared Thermographic Survey Of Building Moisture
Due to evaporative cooling, areas that are wet usually appear cooler than their surrounding areas. However, depending on ambient conditions at the time of the inspection (such as sun exposure, wind, relative humidity, and temperature), typically cooler patterns or wet areas may appear warmer than their surrounding areas. Infrared imagers can detect this heat and “see” the warmer or cooler patterns, allowing the thermographer with proper training and additional tools to interpret those patterns correctly.
Qualitative Infrared Thermographic Survey Of Building Cooling or Heat Loss
Areas with missing insulation most often appear lighter (warmer) during warmer days when the building’s cooling system is in use. They most often appear darker (colder) during colder days when the building’s heating system is in use. It is possible to see an anomaly that might appear as a location of missing insulation, but actually indicates active moisture. It is possible to differentiate between missing insulation and active moisture by utilizing specialty tools such as moisture meters. Depending on conditions at the time of the inspection, such as sun exposure, wind, relative humidity, and temperature, patterns may reflect artifacts that appear as missing insulation. However, missing insulation usually cannot be confirmed without destructive testing, which is commonly beyond the scope of this survey. Infrared imagers can detect and “see” the warmer or cooler patterns, allowing the thermographer with proper training and additional tools to interpret those patterns correctly.
Above is a sample of the same area (visual image on the left and thermal image on the right). Looking at the visual image, nothing looks apparent, however this galvanized water heater displays a very hot area in the middle. Is this a flaw or an especially hot area on the metal? Luckily, it is just some white paint accidentally smudged on the pipe, and it is reflecting rather than emitting infrared light.
Examples of Thermal Inspection Applications
- Water intrusion: scanning the interior of a home with a thermal camera can reveal excess moisture due to plumbing or window leaks. Wet areas are cooler and therefore will stand out on the surrounding dry surface.
- Insulation deficiencies: temperature differences will be detected when missing or improper insulation is spotted when scanning wall or ceiling surfaces.
- Roofing leaks: scanning a roof can reveal water intrusion and moisture below the surface due to thermal properties of water. Any accumulated moisture will be detected when scanning the roof surface.
- Structural issues: thermal capacity and other qualities of building components’ ma allow for detection when scanning walls and floors with a thermal camera. With the right conditions, missing structural and portions of components that are damaged can be detected when scanning the floors and ceilings.
- Electrical systems: A deficient connection in an electrical component will result in resistance that will show up in an apparent temp elevation when compared to other connections under similar conditions.