Infrared Thermography: (Nearly) A Daily Tool

The potential returns of using IR thermography for retrofitting of existing homes are immense.

March 07, 2008
March/April 2008
A version of this article appears in the March/April 2008 issue of Home Energy Magazine.
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Infrared (IR) thermography as a diagnostic tool for building performance has been under utilized. In the past the expense of the tools—from $25k to $60k—and their technological complexity have made them inaccessible to most contractors. Perhaps the biggest barrier has been due to a limited understanding of how to use the technology effectively and, consequently, a lack of day-to-day experience in diverse conditions. Thankfully, as the cost of the technology has decreased—to under $10k for many systems—more and more people are discovering the remarkable value it has in all stages of energy work for both new and retrofit buildings. And as more people use IR thermography regularly our collective foundation of field knowledge has grown substantially.

A Thermograph Is Worth a Thousand Words

To give you just a taste of what an IR camera and experience in thermography can offer you and your home performance business, throughout this article is a gallery of images along with discussion about the conditions existing during the inspections and the issues raised by each. (Thermographs are courtesy of the author.)

The potential returns of using IR thermography for retrofitting of existing homes are immense:

  1. Prior to bidding a job, it is possible to locate all existing insulation and framing. Estimates become more accurate and work goes faster and more smoothly.

  2. After insulating and air sealing the building, placement and performance can be verified and even more importantly, documented. This will virtually eliminate callbacks, give you a competitive edge, and provide valuable documentation that can be given—or sold—to the homeowner. These steps create added value for the life of the building.

  3. When IR thermography is used in conjunction with a blower door it is much simpler to locate air leakage and bypasses than with the blower door alone. As with insulation, it is also possible to test the air sealing work after it is completed and to document its effectiveness.


For new construction, verification of the performance of installed insulation and air sealing materials is itself typically justification enough for the investment of time and education IR thermography requires. The “high-tech” approach combined with the value of the documentation may add significant leverage in the competitive markets of both home performance contracting and real estate.

Although the cost of an IR camera has dropped to under ten thousand dollars, it still represents a significant investment for many contractors, insulators and weatherization agencies. Add to this the cost of the training required to learn to use it effectively and the time needed to conduct an inspection. As with any investment it is useful to know real costs:
  • Training: a minimum of two days is recommended along with several weeks of on-the-job training. Cost will vary.

  • Number of inspections: assume, with planning, you conduct 300 inspections per year (average 2 inspections per day on each of 150 working days per year). The cost of the camera alone for inspection works out to about $5!
  • Cost per inspection: assuming reasonable labor costs, travel between jobs and an additional hour or two on the jobsite, the average cost of an IR thermography inspection can be under $100.
What are the returns? You’ll need to calculate them but it quickly becomes clear, I believe, that for either new or retrofit work, an inspection, even if two are required, is a reasonable investment with large returns.

What it Takes to be a Pro

I have written in detail about the technical aspects of IR cameras and how to use them in an earlier article (see “Breakthroughs in Infrared Cameras,” HE Jan/Feb ’06, p 17). With this article, I want to talk about the “art” of using an IR camera. The first step is to get some training.

In addition to the essential knowledge of buildings and how they work—or don’t work—you must understand the basics of IR thermography and related heat transfer. This foundation in applied physics is essential to success and will require a day or two of training by a qualified organization. Training and trainer qualifications should comply with standards of the American Society for Nondestructive Testing (ASNT). The only way you will grow your own expertise is by using IR thermography often, preferably every day. Some days will be easy and you’ll get great results. Others will be difficult or impossible but you’ll learn a great deal about how to get better results. It is also essential to get continuing education, both the kind that comes from drilling a hole or two in the wall you just inspected, and the kind that comes from sitting down with other thermographers to compare notes.



Certification is generally not required although ensuring all thermographers are qualified is in all of our best interests. The only viable certification in North America at this time is based on the standards of the ASNT, which prescribes the training, experience and testing required for compliance.

Once you understand the basics of the camera’s operation, such as focusing and making manual adjustments, you can really begin to push the limits without getting into trouble. For instance, if the building is changing temperature, as it often does in the course of an inspection, you can use the differences in thermal capacitance between the framing and the insulation, in addition to the conductive differences, to identify problems.



John Snell of Snell Infrared, Montpelier, Vermont has trained thousands of people to use the technology in the past 25 years. His company works with all the major suppliers of IR systems to provide their customers with training, while remaining 100% independent of the sale of any particular product.


For more information:

To learn more about IR cameras, call Snell Infrared at (800)636-9820 or visit the Snell Infrared Web site at
www.snellinfrared.com.

These two highly recommended standards are available for download for a fee:

ASTM C-1060 Standard Practice for Thermographic Inspection of Insulation Installations in Envelope Cavities of Frame Buildings. Go to: www.astm.org.

ISO 6781 Thermal Insulation, qualitative detection of thermal irregularities in building envelopes Infrared method. Go to: www.iso.org.
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