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Thermal Imaging: The Things You’ll See

Homebuilders and remodelers should be taking advantage of thermal imaging—it’s a powerful and economical way to show customers firsthand the heating and cooling losses that are costing them big money. 

With more and more homeowners eager to make energy-efficiency improvements, and the price of infrared technology (which is at the heart of thermal imaging) continuing to fall as performance increases, it’s a technology that belongs in every contractor’s toolbox.

“It makes a heck of an impression on some customers just to be able to show them the information graphically,” says Randy Dinsmore, project coordinator with Goodrich Construction in Mankato, Minnesota. 

Goodrich specializes in remodeling, restoration and home improvement, and Dinsmore has been using thermal imaging there for nearly a decade. “It’s good for documenting problems, but it’s much more useful for me in terms of diagnostic work and in terms of sales and informing customers,” he says.

Thermal imaging provides an inside look at the real-time performance of windows, walls, doors and other building components. By highlighting differences in temperature, the technology can help find the extent of water damage and other hidden problems, but it’s even better at showing energy leakage due to both convection and conduction. Using thermal imaging also helps homeowners see contractors more as efficiency experts and less as salespeople.

“A lot of my customers have the idea that windows are their big source of heat loss, but that’s usually not the case,” Dinsmore says. “Usually the biggest gap in the building envelope that I find is the connection between the masonry foundation and the wood structure. That connection typically was not done very well when it was new and has not improved with time—and it’s not very visible.”

“Even with a modern home built with floor trusses, that rim joist area leaks like a sieve,” Dinsmore says. “[The infrared camera shows] people where their house leaks and the advantages and disadvantages [of] various construction techniques.”

With a thermal-imaging device, Dinsmore can show homeowners the warm moisture being driven through fiberglass insulation against the cold chipboard at the rim of the trusses, where it then condenses. “We see a lot of rot and deterioration that people think are leaks, but really it’s a weather system that’s going on inside their home,” he says. 

Professional home remodelers might be familiar with the telltale signs, but homeowners appreciate how quickly a few thermal-imaging shots help them understand the problems and then buy in to the solutions.

How thermal imaging works

Originally developed in the 1960s for military applications, the technology is actually similar to the now-ubiquitous digital camera used for visual photography. “Really, today’s thermal imagers function much the same way that a visual camera does,” says Joseph Rocchio, worldwide internet business manager for FLIR Systems Inc., which specializes in thermal-imaging systems and other technologies that enhance perception and awareness. 

“A visual camera passively collects light through the lens, which then impacts an array of detectors,” Rocchio says. “The photons impacting the detectors change how much current moves through each detector, and the information we get from that is rendered into an image. That’s really in essence what a thermal-imaging camera does too—it’s taking something we ordinarily cannot see and making it visible.”

Of course, some of the components are a little different. For example, a person can’t see through the lens of a thermal camera. That’s because instead of being made of glass, the lens of an infrared camera frequently is made of the metal germanium, which is a good transmitter of infrared energy but blocks out most visible light—the next highest range in the electromagnetic spectrum.

“The thermal imager gathers infrared energy, which then impacts the individual detectors that make up the pixels of the image and, based on how that changes the current flowing through those pixels, we can calculate a temperature,” Rocchio says. “Then the operating system essentially ‘paints by the numbers’ to produce the visual image that a user sees on the display.”

Technological advances, falling prices

Highly sophisticated thermal-imaging systems can cost $20,000 or more, but several varieties introduced in recent years for contractor and homeowner use are between $200 and $300. There’s even one that’s a plug-in for smartphones.

Much like visual cameras, the big differentiators in thermal imagers today are resolution, sensitivity and the thermal equivalent for depth of field.

“Often, higher resolution is what you’re paying for as you step up from a $200 camera into the $1,000 range,” Rocchio says. “But sensitivity also matters. If the camera’s not [very] sensitive from one pixel to the next, the image kind of blends together. 

“For example, if I put my hand against the wall, then pull it away and look at the wall with a camera that’s not very sensitive, I’ll just get a blurred image of a heat spot,” he says. “With a more sensitive camera that can see the fine changes from pixel to pixel, I get much more definition. I can really see the outline of my hand when I pull it back.”

Another difference among cameras is how much temperature data they provide. Spot thermal cameras register a highly accurate temperature but only for the area defined by crosshairs on the display. The additional color gradients in the image simply show whether other areas are relatively cooler or warmer, and that may be all you need for locating hot and cold spots.

For more comprehensive data, cameras are available that have been radiometrically calibrated, which means that each pixel is calibrated to give accurate temperature data. This is helpful when it’s important to capture an image and later be able to read the exact temperature, such as in industrial and electrical distribution applications.

In fact, noncontact thermal measurement has been widely used in various industries for years. The technology has great benefits in terms of safety and accuracy, but industrial-strength thermal imagers also tend to be relatively expensive.

Looking at the big picture

Using thermography to identify energy leakage in a building envelope is another area where the higher-capacity cameras are useful. Jim D’Aloisio, principal for consulting engineering firm Klepper, Hahn & Hyatt in East Syracuse, New York, purchased his infrared camera more than 10 years ago. 

Since then he has evaluated more than 50 building envelopes to identify energy leakage through either conduction (due to thermal bridging or lack of insulation) or convection (air leakage or air movement within the envelope). Using the more-expensive calibrated type of camera allows him to quickly capture large quantities of data.

“I don’t adjust the color scheme or temperature range at all. I just make sure it’s focused, and I click away because back in the office you can manipulate the images, choose your temperature range and identify points [in which] you want temperatures,” he says. “The software just grabs information from the image that you capture in the field.”

D’Aloisio has also used thermography to evaluate roof membranes, using the weather to his advantage. “If you use it in a certain way, you can get the infrared camera to identify pockets of moisture under the membrane. It’s because of the thermal mass properties of water,” he says. “You need a warm, sunny day. When the sun sets and it gets cold, the temperature changes, and you can see the areas that are still warm because of the thermal mass of the water. Under the right circumstances, that works like a charm.”

Another good application D’Aloisio has found for thermal imaging is building-envelope commissioning. “When the construction of a building is finished, this is a good way to just do a quick check to see if there are any big violations in the envelope,” he says. But overall, identifying opportunities to improve building performance are perhaps the best, most widely accepted use. 

According to D’Aloisio, using thermal imaging to check building-envelope performance “has nothing to do with reducing the cost of design and construction. It’s got everything to do with long-term performance.” The contractor who helps the homeowner—or any owner—in that regard is likely to have a repeat customer for years to come.

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