Hopefully many of you tried my suggestion last week of filling a mug with hot coffee or tea and observing it with your imager as it went through a thermal cycle. If not, please do so as there are many valuable lessons to be learned. Also useful is distilling the temperature changes for the mug and the hot liquid and watching their interplay as they teach us about capacitance, heat flow and temperature.
There is a growing interest in our industry to be able to use the surface temperature of buildings as a way to calculate conduction, or more accurately resistance to conductive heat transfer (R-value). With this information in hand, they hope to plot the energy cost for conditioning a building. This is a great idea that, is not as simple as some would have us believe, unfortunately.
Certainly this sort of thing is often done in a laboratory where all the variables are known and controlled. In fact, it isbasically the way scientists determine the standard conductivity values and R-values for most materials and products we use every day, everything from insulation to frying pans! The process is a simple one in which a stable, known temperature difference is created across the material and the flow of energy is measured. Again, I emphasize that all conditions are carefully controlled and all variables are known and monitored.
Possibility vs. Probability
In the real world, however, especially when “home energy audits” are being done from a moving vehicle or aircraft, the task is much more difficult, to be honest, simply impossible. As a good friend of mine says, “possibility does not imply probability.”
While it would be wonderful if accurate R-value calculations actually could be determined from thermal images in this way, they cannot. My fear is that these attempts will become more widely used or, more likely, misused. Even more troubling than people just experimenting with these processes is the fact that some would like to patent software to automatically make the calculation of these energy transfers. I fear we will all be “tarred with the same brush” and discredited by their inaccurate results.
I don’t want to be a naysayer. I freely admit there is much I still have to learn. If anything, I’m more aware of that fact now than I was nearly 30 years ago when I first used an imager. But in that time, I’ve also seen too many enthusiasts claim they can do things I’ve found to be impossible, limited either by the tools we had/have or the physics of the situations. “Correlation does not always imply causality,” as my friend also says.
So take an hour and sit down with your cup of coffee or tea and your imager and think about what amazing things we can do and what is not so easy.
I’m not sure where we will journey to next week in this blog. Where would you like me to take us?
John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner