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Tip written by: Infraspection Institute

Solar-driven infrared inspections of insulated structures and roofs must be performed when sufficient Delta T is present. Knowing how to gauge when this window of opportunity is present is critical to the accurate collection of data.

Infrared inspections of structures often utilize solar loading to create temperature differentials necessary for the inspection. Common applications include moisture inspections of roofs and walls, structural inspections of CMU walls, and gauging product levels in tanks and silos. Often, these types of infrared inspections are performed during evening hours following a sunny day while the structure is cooling.

The time frame during which solar-driven infrared inspections may be accurately performed is often referred to as the ‘scanning window’. The scanning window is said to be open when conditions permit the collection of accurate data. A number of interdependent factors will determine when the scanning window opens and closes. These include, but are not limited to: target construction, amount of solar loading, local weather conditions, and imager sensitivity.

To determine when the scanning window opens, a thermographer should initially isolate an area with a small delta T indicative of an exception. For moisture inspections, this might be an area that is confirmed to be minimally wet. Using this area as a benchmark, the thermographer can periodically re-check this area during the inspection to determine if a Delta T remains. In general, the disappearance of a Delta T in the benchmark area will indicate that the scanning window is closing.

Infrared inspections of building envelopes and roofs are two of the many topics covered in the Infraspection Institute Level I Certified Infrared Thermographer® training course. For more information on other course offerings, call 609-239-4788 or visit us online at Infraspection.com.

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