Heat. What is it and how can we see and measure it?

A thermal selfy!

A thermal selfy!

Last week I spent 34 hours over a five-day timeframe learning about infrared thermography, or the ability to see and measure the radiation we all know as heat, and as a result I am now a Certified Level One Thermographer.

So what does this mean? It may be easiest to compare thermography to the taking of regular pictures with, well… regular cameras. We all can understand that a camera records an image that we can see with our eyes… the reflected light that our eyes see and our brain interprets as shapes and colors. Well, heat radiation is simply a different portion of the electromagnetic spectrum, invisible to the human eye but very present and visible to equipment properly designed to ‘see’ it. And an infrared camera has the technology to ‘see’ an infrared image… to see heat being emitted by a surface.

Everything that is above absolute zero emits infrared energy… a measurable amount of thermal radiation. Ice cubes give off thermal radiation, as does a human face, and an infrared camera can detect that radiation.

At least one untrained and uncertified home inspector, when asked about his use of an IR camera, said “what’s to know… red is hot and blue is cold”. Well yes and no.

Some people have the mistaken belief that an IR camera can see inside walls. Not true, anymore than a regular camera can. An IR camera sees infrared energy emitted from the surface of the item being viewed. What a Certified Thermographer might be able to extrapolate is the heat impact on the wall surface of things inside the wall, such as missing or wet insulation. However – and significantly limiting this functionality in our climate – is the need for the temperature delta/difference between outside and inside to be at least 15 degrees. Without that delta, nothing is revealed because not enough thermal energy is ‘moving’. With that delta, maybe something can be ‘seen’, with an emphasis on maybe.

It’s also true that just because thermography ‘sees’ heat being emitted from a surface, it doesn’t mean the surface is telling the truth. With everything around us giving off thermal radiation, it is easy to be tricked when a surface is actually reflecting the thermal radiation of something else. An untrained thermographer can actually pick up the reflected radiation of their own body, or if trying to record the specific temperature of the top of an item that is outside and has a low emissivity – the ability to emit its own heat – an untrained thermographer might be surprised at how cold the item appears… because it’s literally reflecting the thermal image of outer space!

So again… what does this mean? Anyone who suggests that infrared thermography can see inside walls is either untrained or not telling the truth. Can an infrared camera possibly add value to a home inspection? Under the right circumstances and in the right hands, yes. If infrared thermography is of interest to you for your inspection, my only recommendation is to make certain the person holding the camera is a Certified Thermographer as defined by the guidelines of the American Society for Nondestructive Testing (ASNT). Because otherwise… red is hot and blue is cold.

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