The Myth of Infrared, Continued

In the following I’ll discuss a number of the limiting factors which help explain my position that I.R. imagers are not an effective tool for use during a pre-purchase home inspection.
  • The operator of the imager must have a sound knowledge of building science and have been trained to take adequate images based on building science for interpretation. 
  • Since these imagers don’t see water or mold, as many people have been led to believe, and are in reality a diagnostic tool, it’s important to know what you’re really looking for. 
  • In order to get a usable image, the accepted standards say there must be a 15° F differential across the surface one is looking at. For example, if taking the image of the wall of a house, there must be a 15° F difference between the side of the wall being viewed and the outside/backside. 
  • A wind of over 12/mph can change the temperature characteristics of a building, making imaging ineffective. 
  • The thermal effect of the sun shining on the house can play a major role, making imaging ineffective. Remember, a house has at least four sides in relation to the intensity of the sun’s radiation, each having a different thermal load. 
  • Exterior imaging, including roofs, is best done around 11 p.m. or shortly before daybreak due to thermal loading of the building and building surfaces. 
  • In order to take an adequate picture of an electrical panel, the electrical system must be at 60% load. A properly designed panel should not exceed 80% load, so this means just about every possible device in the house that uses electricity needs to be turned on and operating. Without following this basic procedure, it’s quite simple to take an image and get inaccurate information. Simply by plugging in something like a toaster, with the balance of the electrical panel at rest, it’s very easy to take an image and make it look like the breaker feeding the toaster is over heating and ready to burn up. 
  • Reflected radiation, which can be one of the biggest challenges when taking an image is one of the major causes for misinterpretation of an image. Would you like to go on a ghost hunt? Without going into detail, I can show images of a ghost in just about any room of your house (sounds like an opportunity for another TV program!).
Note: When I’m saying “ineffective” or “must” in the above points, it has to be understood that these are not conditions that can be changed on the imager like adjustments on 35mm camera. These are environmental conditions that have to be right at the time the image is taken. If the control conditions are not right, they have to be created, which is not possible during a pre-purchase home inspection. Hence I state my case, contrary to promotion by our TV celebrity, infrared imaging is not a viable part of a home inspection. Is there a chance of getting some cool images? No problem, but that’s not thermography. I will go as far as stating that any home inspector who is arbitrarily offering thermography as part of their pre-purchase home inspection is bordering on fraud. About the only possible place that I.R. imaging might be used relatively consistently during a pre-purchase home inspection is at the base of a finished basement wall.
So let’s do the math: imager @ $5,000 + training @ $2,000 = $7,000. Then, once moisture is suspected, a moisture meter is required to confirm that it is moisture, so that’s $7,000 + moisture meter @ $500 = a $7,500 moisture meter. That’s a lot of money to spend when most professional home inspectors already have a moisture meter in their tool kit and know how to use it.
Now don’t take any of this as me saying thermal imagers are not a good tool to be used in the practice of building science. They are a fascinating tool and have many legitimate applications in residential problem-solving when used properly and under the right conditions. If you’re looking for air leakage or insulation issues, adding a blower door to the equation takes things to the next level. A thermal investigation of a typical house will cost more than an average home inspection.
 Excerpt from the book - Buy or Run - by Bruce McClure, pg. 92-97