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Three Causes for IR Skepticism

In my nearly 30 years in this industry, I’ve seen lots of fads and gimmicks come and go.

All too often these fads seem to be the creations of over-zealous marketing departments who don’t have the practical scientific understanding to know how the technology is really used.

For example, the recent introduction of an imaging system (by a company that competes with Fluke, just to be transparent!) that “talks to” the Apple iPad may be in this category. Or is it just the forward march of technological progress that actually makes life easier?  Ultimately, only time and us practicing thermographers will be able to tell!

While most aerial infrared has little value for understanding the energy use of a building, streetscape thermography can have value. Still, understanding the root cause of a variation in temperature requires more than a gimmick or a “drive by.”

However, there are 3 “bone-headed” ideas that I find much more disturbing.  Here are the top 3 gimmicks to watch out for:

Aerial Infrared
There is a resurgence of aerial infrared being used for home energy auditing. These techniques did not work in the 1970s and 80s and they still don’t work today.  But that has not stopped us from spending millions on these kinds of projects, Boston being the most notable of late (read full Boston aerial infrared article here). Interestingly enough, this project may get derailed by more bad science as some citizens are worried it could result in “seeing into their homes”!

Thermal Images from Street Level
Back into vogue are thermal images of buildings done from street level. This is made even more popular by Google’s visual version. While street thermography is still of limited value, it can at least provide some useful data about the front of the home or building.

Truthfully, both aerial and street thermography might be useful tools to market energy efficiency, but the risk of charlatans is great. In the end, thermographers must get inside the home to really understand what is going on. Anything less than that will not yield information that can produce significant energy savings.

Image Subtraction
Lastly, another monster back from the thermal graveyard is “image subtraction,” this time to find air leakage. The technique involves subtracting each data point of the current image from each data point of a previous one. If alignment is perfect, this is a brilliant way to see changes in the data. It has been used extensively in materials evaluation as well as machine analysis.

You don’t need image subtraction or other gimmicks to locate air leakage. There is not quick fix or shortcut! What is needed are good techniques, an understanding of building dynamics, a blower door and an infrared imaging system.

Recently, I heard it was being heavily promoted as “the only way to see air leakage in buildings”. Not only is this NOT true—air leakage is often very easy to see and understand with depressurization—but the technique limits us significantly by necessitating the use of a tripod. I’ve looked at thousands of buildings and, when I really need one, I will certainly pack a tripod. Unlike the academics who are promoting this silliness, however, I have to be practical and thus use a tripod only when really necessary.  Using frame averaging for long telephoto shots or when taking images over a period of time are good examples. Using image subtraction for locating air leakage is just crazy!


In the end I have to always ask myself “what really works?” It is clearly not marketing fluff! The real answer remains unchanged:

  • A good quality imager appropriate to the task
  • Basic training and experience, and
  • An inquisitive mind

I hope these odds and ends have helped develop your inquisitive (and hopefully slightly skeptical) mind—the best tool any of us can have!

Thinking Thermally,
John Snell—The Snell Group, a
Fluke Thermal Imaging Blog content partner

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