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Infrared thermography has become a standard tool for locating trapped moisture inside a commercial roof system without opening it up section by section. The underlying principle is straightforward: wet insulation retains heat differently than dry insulation, so after a sunny day warms the roof surface, a wet area will still be radiating heat after sunset while dry areas have cooled off faster. A thermal camera captures that temperature differential as a visible pattern, letting a trained operator mark suspect zones for further investigation.
Timing and conditions matter a great deal for a reliable scan. Surveys are typically conducted at night, several hours after sunset, following a day with enough direct sun exposure to heat the roof assembly and enough temperature differential between day and night to create a measurable signal. Clear skies, low wind, and a dry roof surface all improve accuracy, while cloud cover, standing water on the surface, or a roof with reflective coating can distort or mute the readings. Operators performing this work are often trained through programs affiliated with organizations such as the Infraspection Institute, and the scan itself is generally paired with a visible-light photograph of the same area for reference.
An infrared scan identifies where moisture is likely present, but it does not by itself confirm moisture content or explain how it got there. That confirmation typically comes from core cuts or a moisture meter probe at representative locations within and outside the flagged zones, which verifies the thermal reading and gives a physical sample of the affected insulation. This two-step process, scan followed by verification, is what makes infrared surveys defensible as documentation in a claim rather than just a visual impression.
On a roof with a recent storm event, an infrared survey can help separate moisture that predates the loss from moisture that appears concentrated around storm-related punctures or seam failures, though drawing that line usually requires correlating the thermal pattern with membrane inspection findings and, where available, prior roof condition reports. A roof with a long history of ponding or previously repaired leaks may show broad moisture patterns unrelated to a specific weather event, which is why the survey works best as one piece of evidence among several rather than a standalone conclusion.
Equipment used for infrared surveys ranges from handheld long-wave cameras used by an inspector walking the roof to drone-mounted systems that capture a wider area more quickly on larger buildings, and calibration of the equipment along with the operator’s experience both affect how reliable the resulting imagery is. Ballasted roofs and roofs with reflective coatings tend to be harder to read accurately because the ballast layer or coating changes how the surface radiates heat, and gravel in particular can mask a moisture pattern that would otherwise be clearly visible on an exposed membrane. These limitations are part of why an infrared finding is treated as a starting point for further investigation rather than a final determination on its own. Practices such as ASTM C1153, which describes standard methods for locating wet insulation in roofing systems using infrared imaging, provide a reference point for how a survey should generally be conducted and reported, though individual thermographers and roofing consultants may layer additional steps on top of that baseline depending on the specific building and equipment involved.
This article is general education about how the appraisal process commonly works. It is not legal advice, and specific procedures can vary by state and policy.
Russ Lis is a working property insurance appraiser and umpire based in Minnesota, serving clients nationwide. Contact Appraisal Resolution.