Home Inspector Aims A Thermal Camera At A Mirror Next To A Mini Split And Cannot Figure Out How A Reflection Shows A Cold Spot

Every now and then, a person who does the same job every day runs into something that stops them in their tracks. That is exactly what happens in a reel from @inspectorbill_33, who was inspecting a house when something really strange showed up on screen.

A home inspector's thermal camera reel cover, beside a stock thermal image showing heat colors.

“I see something really strange I’ve never seen before,” the inspector says. It is not a leak, a crack or a wiring problem. It is a cold spot that appeared in a place it should not have been able to appear, and the inspector was left wondering how it was even possible.

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What The Inspector Was Doing

The setup is simple. The house has a mini split, the wall mounted unit that heats and cools a room without ductwork. The inspector checks mini splits with a thermal camera, a tool that shows temperature as color on a screen. Pointing it at the unit, the inspector can see temperatures coming out of it. That is normal, and exactly what you would expect.

Then came the surprise. Next to the mini split was a mirror. Looking in the mirror at the mini split, the thermal camera read the cold spot there too. The inspector’s question to the audience is the whole point of the reel: how is the thermal camera picking up the cold spot? The answer, is one word. A reflection.

Why A Mirror Can Fool A Thermal Camera

Most of us think of a mirror as something that reflects light we can see. But a thermal camera does not see ordinary light the way our eyes do. It reads heat energy given off by surfaces. And it turns out that a shiny surface like a mirror can bounce that heat energy back, in much the same way it bounces visible light.

So when the camera looks at the mirror, it is not only measuring the temperature of the glass. It is also picking up the image of whatever the mirror is reflecting, which in this case was the cold air coming from the mini split. The camera showed a cold spot in the mirror that did not really belong to the mirror at all. It belonged to the unit it was reflecting.

That is a useful lesson for anyone who has ever bought or borrowed a thermal camera. Shiny surfaces, like mirrors, can show up as false readings. If a spot on the screen looks odd, it is worth asking whether the camera is looking at the surface itself or at something being reflected in it.

Why This Matters For Home Buyers

Thermal cameras have become a popular tool in home inspections. They can help an inspector spot things the eye cannot see, like a hot or cold area on a wall, ceiling or appliance. But the tool is only as good as the person using it. An inspector who knows how reflections work will not mistake a mirror image for a real problem, and will not tell a buyer there is a cold spot where there is none.

That is a good reason to hire an inspector with experience. A camera can show you an interesting picture, but it takes a trained eye to understand what the picture actually means. The reel is a small example of that: the inspector saw something odd, stopped to think about it and landed on the answer: a reflection.

What Homeowners Can Take From It

Know your mini split. If you have one, pay attention to how it sounds and how the air feels when it runs. A change you can feel is worth mentioning to a technician.
Ask about the tools. If an inspector uses a thermal camera, ask what they are looking for and how they confirm what they see.
Be careful with DIY readings. If you borrow or buy a thermal camera, keep in mind that mirrors, windows and other shiny surfaces can reflect heat and give you a false picture.
Do not panic over one image. A single odd reading is a reason to look closer, not a reason to assume the worst.
Look from more than one angle. The cold spot in the reel showed up in the mirror, which is what pointed to a reflection. Changing your view can change the answer.

The Fun Of The Job

There is something charming about an inspector who stops to wonder about something new. The reel is not about a defect or a warning. It is about curiosity, and about how it is worth stopping to think when something looks odd.

It is also a reminder that the world is full of small surprises if you look closely. A mirror next to a mini split is hardly a dramatic scene. But through a thermal camera, it turned into a puzzle. If you enjoy little mysteries like this one, you can find more at @inspectorbill_33.

Willow and Hearth