A question for the record
Twenty below zero. Wind tearing across a Detroit rooftop. Your hands are numb, the equipment is cold, and every instinct says, Get the data and get down.
You enter 0.95 for emissivity and keep moving.
Was it correct—or merely convenient?
Confidence is easy.
Knowing what deserves to be questioned is harder.
Andrew C. Thacker
The Discipline of Defensible Thermography
Technology is no substitute for judgment.
Ordering InformationExcerpt One
The detector cannot determine whether reduced radiance came from a cooler surface or a lower-emissivity surface, because both can produce a lower arriving signal. It cannot determine whether elevated radiance came from a hotter surface or a reflective surface mirroring a hotter environment, because both can produce a higher arriving signal.
The detector receives radiance. The thermographer must decide what it means.
Excerpt Two
The infrared camera records only a single moment in time. The roof, however, has been writing its story for years.
Every repair, every patch, every depression, every rooftop unit, every change in material, and every season of weather leaves evidence behind. Our responsibility is to understand enough of that story to interpret today’s thermal evidence correctly.