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Thermal Imaging for Building Diagnostics

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Thermal Imaging for Building Diagnostics

An FLIR Thermal camera attached to the bottom of smartphone.Photo 1: Thermal camera on a smartphone.

Have you ever wished that you could see into your walls? Would you like to find out where your energy losses are? Although they don’t offer Superman-grade X-ray vision, modern thermal cameras can help builders, remodelers, and energy professionals identify many construction defects and other home problems that cause energy waste. Detecting energy leaks during construction allows builders to remedy these deficiencies early on, when they are less expensive to fix. Imagine how much more efficient builders could be if they could find a significant air leak in a structure’s insulation before the wallboard is installed.

Although thermal cameras have been available for years, they were cost prohibitive for most businesses, with price tags often exceeding $10,000. As a result, thermal camera use was mostly limited to energy auditing or consulting firms.

Nowadays, however, thermal cameras are widely available, and for only a few hundred dollars, builders and designers can own a thermal camera that docks to a phone or tablet to inspect and verify building quality and performance during construction. These small, inexpensive cameras allow construction teams to quickly inspect their work without waiting for an engineer or inspector to come to the site.


Left: Thermal image of the inside of a door, where the cool areas around the edges of the door are visible. Right: Thermal image of the outside of a door, where the warm areas around the edges of the door are visible.Photo 2: Left: Inside shot of an exterior door showing colder areas around the perimeter. Right: Outside shot of the same door. Note that the color scale has shifted, as the perimeter is now relatively warmer than the surrounding area.

Thermal image of a ceramic floor with electric radiant heating coils visible below.Photo 3: Electric radiant heat operating under a ceramic floor.

The camera works by presenting a color scale showing relative differences in temperature, with red or white as the warmest and blue or purple as the coolest. (The camera’s software allows users to customize the color scheme.) The camera is very sensitive and will detect differences of only a few degrees.

Thermal cameras are best known for their ability to detect energy leaks in homes. Photo 2 shows a door with poorly functioning weather stripping.

Although detecting energy leaks is important, determining construction quality or performance may be a more valuable use for thermal cameras. During construction, thermal cameras allow builders to verify energy performance at a stage when corrections are easiest to make. Photo 3 shows a radiant heating system beneath a ceramic floor (the square in the upper left of the photo is a small rug). Because repairing a radiant system after the flooring is installed is quite expensive, contactors can use a thermal camera to ensure that the system the system is connected and operational before flooring is in place.


A Thermal image of a coffee machine pouring coffee into a mug, in which the heat flowing through the electrical cord and the coffee are visible.Photo 4: The office coffeemaker dispensing its goodness.

Thermal image of a wall, in which the studs and exterior outlet are visible, as is heat loss in the corner. The table lamp and picture frame on the wall are also visible.Photo 5: Wall showing corner heat loss, studs, and exterior outlet.

Thermal image of a plumbing manifold and tubing, where the tube through which hot water is flowing is visible.Photo 6: Close up of a plumbing manifold and tubing when hot water is being used.

Thermal images can also help identify water leaks and some electrical problems. The moist areas of a wall with a water leak will show greater heat loss because water is a better conductor of heat. Thermal cameras are often used to identify outlets that are hotter than others because of overloaded circuits, damage, or loose wiring.

The thermal camera will also indicate what lies behind walls. In Photo 5, the studs can be seen because the wood, which has a lower R-value than the spray-foam-insulated walls, serves as a “thermal bridge” for heat flow. The evidence of this bridging is clearest in the corner (on the left). In the lower-right corner, an outlet on the outside of the wall is also evident.

Photo 6 shows a plumbing installation using cross-linked polyethylene tubing and a manifold system. The camera allows the builder to easily identify and label hot water lines.


Thermal image of a light switch in operation and with visible electricity.Photo 7: Light switch showing temperature changes while in operation.

Left: Thermal image of a door in which the uninsulated mail slot is visible. Right: Thermal image of a door in which the insulated mail slot is visible, as is air leakage under the door.Photo 8: Left: Door showing energy loss through an uninsulated mail slot. Right: Mail slot after insulation. Note the air leakage at the bottom of the door.

In the left portion of Photo 8, the mail slot in the door shows significant energy loss. To address this loss, the slot was filled with foam insulation to prevent airflow. (The home has a separate mailbox.) The right portion of Photo 8 shows the door after insulating the mail slot. The bottom of the door still needs weather stripping to address air leakage under the door. Both photos were taken from the inside of the home.

Left: Thermal image of a floor on which two footprints are visible. Right: Thermal image of the Old Faithful geyser in Yellowstone National Park, in which the hot water coming from the geyser is visible. Photo 9: Left: In addition to their ability to improve the construction process, thermal cameras are also fun to use. Here, the footprints show where bare feet have warmed this wood floor. Right: Hot water ejected from the Old Faithful geyser in Yellowstone National Park.

The thermal camera’s low cost allows builders to identify needed work and then demonstrate the successful completion of the work, which will both improve the quality of the work and inform the customer. Using a thermal camera demonstrates that the builder is technologically savvy and creates an opportunity for follow-on business by helping homeowners prioritize future energy efforts. The photos can be easily shared with the homeowner, who will likely show them to friends and neighbors.

Although they lack the full capabilities of a high-end thermal camera, smartphone-based thermal cameras allow builders to rapidly identify problems and document performance. The camera is likely to pay for itself quickly considering the potentially significant cost of repairing even a simple construction problem. Few building diagnostic tools will provide as much immediate value and enjoyment.

Published Date: 18 March 2019

The contents of this article are the views of the author(s) and do not necessarily reflect the views or policies of the U.S. Department of Housing and Urban Development or the U.S. Government.