As an energy rater, my thermal imaging cameras are my most-used tools. I use them to find missing and poorly installed insulation in walls and ceilings, to detect air leakage during blower-door tests, to look for leaking pipes and roofs, and even just to explore the temperatures of everything around me. I purchased my first thermal imaging camera in 2009. It was an Extech i3 made by Flir. The $1200 camera had a resolution of 60×60, 3600 pixels, and no digital overlay.

If you don’t understand any of those terms, that’s OK—you will have a basic understanding of thermal imaging by the end of this article. But know up front that you can now purchase a camera with twice the resolution of my 2009 camera for $600 or less.

Getting started

Let’s begin with a common misconception. A thermal imaging camera cannot see through walls like they show on bad TV. Thermal imaging cameras are a type of infrared (IR) camera that measures heat emitted by objects. In other words, thermal imaging “sees” differences in temperature within the camera’s field of view. You can see by these different surface temperatures where there is thermal bridging in a wall assembly. You might see wet or even slightly damp areas. Though they are only one type, thermal imaging cameras are often called IR cameras by those in the building industry, and I use the terms interchangeably.

In order to use an IR camera for building diagnostics, you need a temperature difference (Delta T) between inside and outside the structure of at least 10° or everything in the IR image will appear the same color with little information to be learned from it. Bigger temperature differences are easier to discern and create a more dramatic thermal image. If the indoor and outdoor temperatures are…