What Infrared Thermography Actually Shows on a Building

An infrared camera does not see moisture. It does not see mold, and it cannot see through a wall. What it sees is surface temperature, and everything useful about thermography follows from understanding that one limitation.

It remains one of the most valuable tools available on a commercial building, and in Miami-Dade County it is not optional.

Where Florida requires it

Miami-Dade County requires infrared thermography on the electrical portion of a building recertification where the combined service is 400 amperes or greater. The county also sets conditions on who may perform it: a Level II or higher certified thermographer with more than seven years of commercial electrical experience, and a written report as part of the submission.

Broward County does not require it. Under the Building Safety Inspection Program, thermal imaging is left to the inspecting professional to call. That single difference between two adjoining counties catches out owners with property in both, and it is one of several. If your building is in Broward, thermography is a judgment call about value rather than a compliance obligation.

What it actually detects

A thermal camera renders surface temperature as an image. Anything that changes the temperature of a surface becomes visible, which turns out to cover a great deal.

•   Electrical faults. A loose connection, a corroded lug or an overloaded conductor generates heat through resistance. On a panel under load, that shows as a bright spot long before anything smells hot or trips. This is the single highest-value application, and it is why the county mandates it on large services.

•   Unbalanced loads. Three phases carrying very different loads show as three visibly different temperatures. It is a maintenance finding rather than a failure, but it shortens equipment life and it is invisible any other way.

•   Missing or displaced insulation. Gaps read as temperature differences across a ceiling or wall. In a South Florida building this usually shows up as an air conditioning cost rather than a comfort complaint.

•   Thermal anomalies that may indicate moisture. Wet material holds and releases heat differently from dry material, so water-affected areas often appear as distinct cool patterns. Note the careful wording. The camera has found a temperature difference, not water.

•   Air leakage and envelope failures. Conditioned air escaping, or humid outside air entering, leaves a visible thermal signature at the point of failure.

The four things it cannot do

This part matters more than the list above, because almost every misuse of thermography comes from expecting one of these.

•   It cannot see through anything. A thermal camera reads the surface facing it, and nothing behind that surface. It detects what conditions behind a wall have done to the face of the wall. The distinction sounds academic until somebody expects a camera to find a pipe inside a slab.

•   It cannot measure moisture. A thermal anomaly is a candidate, not a finding. It must be confirmed with a moisture meter, and a competent report will say which instrument confirmed it and what it read. An image on its own is a hypothesis.

•   It cannot detect mold. No infrared camera can identify mold growth, and any report implying otherwise is describing something the physics does not support. What thermography can do is find the moisture conditions that allow growth, which is genuinely useful and is a different claim.

•   It cannot assess electrical equipment that is not under load. This is the one that quietly invalidates surveys. Resistance heating only occurs when current flows. A panel scanned at a small fraction of its normal load can look perfectly healthy while concealing a connection that would fail at full demand. A survey performed on a lightly loaded building at the wrong hour of the day can be technically complete and practically worthless.

Why two thermographers can produce different images of the same panel

Infrared is an interpretive tool, not a meter that returns a number. Several variables decide what the image shows, and all of them are set by the person holding the camera.

Emissivity is the main one: different materials radiate heat differently at the same actual temperature, so bare copper, painted steel and plastic in one panel all report differently unless the operator compensates. Reflection is another. A shiny surface can show you the temperature of something across the room rather than its own. Distance, angle, ambient conditions and the temperature scale chosen for the image all change the result.

This is the reason the certification requirement exists, and the reason it specifies Level II rather than simply certified. An uncalibrated interpretation produces a confident image of the wrong thing.

If you are commissioning a thermal survey.  Four questions, none of which cost anything to ask. What certification level does the thermographer hold, and what is the certificate number? Was the electrical equipment under normal operating load at the time of the survey, and what load? Were any thermal anomalies confirmed by a second method, and which one? Will the written report include both the thermal image and a visible-light photograph of the same location? That last one matters more than it sounds. A thermal image without its matching photograph is very difficult for anyone else to act on later.

What a proper thermal report contains

For a recertification submission in Miami-Dade, the written report is part of the package and is read by the county. Elsewhere, the report is what a contractor prices from and what an insurer may later examine.

•   The thermographer name, certification level and certificate number.

•   The equipment used, and the date of its last calibration.

•   The load conditions at the time of the survey, stated rather than implied.

•   Paired images: the thermal image and the visible-light photograph of the same location, side by side.

•   The emissivity setting and reflected temperature used, so another thermographer could reproduce the reading.

•   A stated severity for each anomaly, with a recommended action and a timescale.

•   Anything that could not be inspected, and why. A locked room or an energized panel that could not be safely opened belongs in the report, not in a gap.

Infrared is at its best when it is treated as one instrument among several. It finds things nothing else will find, and it proves nothing on its own.

About the author. 

Raymond Ward is a Florida-licensed Mold Assessor (MRSA-2391), Mold Remediator (MRSR-3879) and Home Inspector (HI1164), and the principal of All Inspections 4U Environmental in Miami, Florida. He is a NORMI member, a CCPIA instructor teaching primarily in Spanish, and a DBPR-approved continuing education provider, developing and delivering courses in mold assessment, home inspection, wind mitigation, radon measurement and commercial building inspection. He has worked in the inspection industry since 2002 and has been licensed since 2012.

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