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Field Test Best Practices: A Resource for Practical Residential Building Science

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Infrared Thermography

Infrared (IR) imaging, or thermography, is a useful diagnostic tool. All materials emit infrared radiation at levels dependent on their temperature. An IR camera is able to capture this radiation in the same way a standard camera captures visible light. Similar to a digital camera color calibration, IR cameras must be used carefully if accurate temperatures are desired. But less care is required for relative measurements, such as looking for cold sections that represent lack of insulation within a wall's stud cavities.

IR Thermograph showing the exterior of
a home

IR Thermograph showing studs and drywall
screws in an exterior wall

Thermography can yield very useful information in field tests. Some limitations of the materials being imaged can be easily addressed. For example, glass is largely reflective in the IR range, so imaging of a window will be very strongly influenced by the temperature of reflected surfaces (such as the low temperature seen on the purple window areas in the right of the above image). Using a strip or two of blue "painter’s tape," a more accurate window temperature can be visualized. Other materials that are difficult or cause inaccuracies include: thin objects, shiny objects of nearly any type, metallic surfaces, and ice.

Use of an IR camera requires skill and practice. To achieve accurate temperatures of any building component, you must focus correctly on it. Most IR cameras' auto-focus features will get you close, but not exactly where you need to be.

Recording an IR image is somewhat slower than with a digital camera, so a tripod is often useful in the field. This also means that accurate temperature visualization of a rapidly-heating or cooling body is not realistic. There are very expensive IR cameras which provide this capability if it is necessary.