Thermal Technology for Roofing Applications

We recently discussed the thermal technology of forward-looking infrared and how roofers can use it to provide inspection services. John Anderson, Product Manager of Security Solutions for FLIR Systems, shared his knowledge here:

Roofing Technologies (RT): Let’s start with the basics. What is thermal imaging and how does it work?

thermal image of flat roof

John Anderson (YES): Normal, human vision is limited to a very narrow, “visible” band of the entire electromagnetic spectrum. The infrared spectrum, also called thermal energy, has a longer wavelength than visible light. A thermal imager / camera is essentially a thermal sensor that can detect small temperature differences, both hot and cold. Thermal imaging cameras allow anyone to see thermal energy (heat), essentially giving the user a superhuman view. Thermal imaging dramatically expands the portion of the spectrum we observe, allowing us to ‘see’ heat even when there is no light.

Everything in the known universe emits, reflects or absorbs heat radiation. A thermal camera converts the measured “heat” data into visible images. In addition to seeing in the dark and detecting invisible heat sources, thermal technology helps users see through fog and smoke. The image produced is known as a thermogram and is analyzed by thermography.

RT: How can this technology be used by roofers?

AND: Thermal imaging is a popular non-destructive inspection technique used in the construction industry. If a flat roof leaks, the damage usually goes unnoticed as water penetrates and soaks the deck and insulation over time. Rot often develops, which can weaken the roof structure and lead to expensive repairs down the road. Considering how difficult it is to find a water leak with the naked eye, thermal cameras can help roofers locate water ingress, find subsurface moisture, and accurately and reliably capture drought. Because thermal imaging is much faster than visual inspection, inspectors can focus on the entire roof, not just the areas at risk. It also allows inspection of nighttime and shaded areas as no visible light is required.

RT: What are the limitations of forward-looking infrared? How can one produce the most accurate results?

AND: There are a number of factors that can affect thermal camera performance and ultimately the outcome of an inspection:

• While a thermal camera can quickly identify potential moisture problems, it is recommended that you also confirm / verify the problem with a moisture meter.
• Thermal cameras come in different resolutions, so different cameras have different limitations. A lower resolution camera requires the operator to get very close to a potential problem area to locate a problem, while a higher resolution camera provides more detail and clarity during an inspection. However, cameras with a higher resolution generally cost more than a lower resolution, so the operator will need to consider which resolution is best for his needs depending on when, where and how he plans to use the device.
• Heat measurements can be influenced by indoor heat sources or by differences in insulation thickness.
• The optimal time to scan a roof, also called the “thermal window”, is when the roof is warming or cooling, usually from early to mid-morning and then again shortly after sunset. Ideally, most roof inspections are done shortly after sunset during a cooling down phase to avoid problems with shade and sun reflection on the roof during the day.

In addition, the best time to perform thermal imaging roof inspections is when there is a high contrast between the air temperature outside and inside the building. This makes it easier to detect possible anomalies. It’s also best to avoid inspections on windy days, as the wind and pressure changes can make it difficult to spot problems. Meanwhile, excessively sunny, hot days can cause solar effects on the roof that can mask problem areas.

RT: What types of thermal infrared products are best for roofers who are just getting started with this technology?

AND: Although handheld thermal cameras have been used by roofers for years to locate water ingress, find subsurface moisture and document drought, the work is time consuming and physical for roofers of all experience levels. Among the many types of portable thermal cameras, we recommend rugged devices that can handle the possible ingress of moisture and dust, as well as any drops on hard surfaces. In addition, contractors must use a thermal camera with radiometric capabilities that allows them to capture the temperature of each pixel in the scene, improving the operator’s ability to locate specific problem areas for further inspection or repair.

Now many roof inspectors are using unmanned aerial drones equipped with both thermal and visual cameras as they can fly over large areas with ease and provide a thorough view of an entire roof in just minutes, which is especially useful for difficult accessible places. range or hazardous areas. Inspectors may still need to rooftop and use traditional testing methods to further assess the issue, but the overall time compared to performing a portable thermal inspection alone is significantly reduced and potentially much safer as the drone pilot can keep his feet safe. the ground.

RT: What training or regulations are required to use these devices?

AND: Laws and regulations governing who can make roof damage recommendations vary from state to state. So when using a drone equipped with a thermal camera, operators should familiarize themselves with local requirements and always work with a licensed professional to ensure that the scans have real, actionable value. In addition, there is a national standard defining the methodology that thermographers using handheld cameras to inspect roofs should use. The standard, ASTM c1153-10 (2015) Standard Practice of Location of Wet Insulation in Roofing Systems using Infrared Imaging, also applies to drone operators.

FLIR also partners with the Infrared Training Center (ITC) to offer certification courses that teach best practices and techniques. It is important that roofers understand how the camera ‘sees’ different roof materials and learn techniques to know when a ‘cool’ spot in the scene is, for example, just cool air or water under the roof membrane. It is important to know how each layer in the roof system affects thermal patterns. The user must understand the mounting of the roof so that they can understand if what they are seeing is a problem or just part of the structure.

RT: What is the life of a typical thermal device if it is used and cared for properly?

AND: There are several factors that play a role in the life of a thermal camera. For roof applications it is necessary to have a rugged camera that can withstand the environmental conditions present on a roof, such as high heat or bitter cold, as well as withstand being dropped on hard surfaces or from one floor level to another .

Many thermal cameras are equipped with a rechargeable lithium ion battery. Therefore, camera managers should make sure to keep the device and batteries away from high temperatures (such as on the dashboard of a truck in the middle or summer), or leave them out in freezing temperatures – all factors that can significantly affect performance . of the battery and thus the life of the camera. A roof inspection device, if properly cared for, can last for many years.

RT: What software is required and how can contractors access the information collected by the camera?

AND: Software is not required to use a device, but is a recommended add-on for editing images and creating comprehensive inspection reports. Users have several options for software – there are free versions available that offer simple image editing and fast reporting, and there are paid versions that offer advanced measurement and image analysis, as well as editing and custom reporting.

Depending on the software, operators can adjust colors, apply spot meters, isolate certain locations within a scene for further inspection, or manipulate an image during post-processing to better interpret a scene for inclusion in a post-inspection report. For large-scale roof inspections, FLIR offers a paid software option that allows customers to batch edit a large number of images, saving a lot of time.

Thermal image of building with half installed metal roof

RT: What variables on the forward-looking infrared devices themselves should contractors be aware of?

AND: For roof applications, there is a national standard that defines the methodology that thermographers using handheld cameras to inspect roofs should use (the aforementioned ASTM c1153-10 (2015)).

For the device itself, there are a few good rules of thumb that roofers should keep in mind when considering a portable thermal camera. Among which:

• A radiometric thermal camera, which means that the camera can detect and measure the temperature of each pixel in the field of view of the respective camera
• A camera with an IP65 rating or higher – a camera that is dustproof and can perform in rain or snow
• A camera that allows you to take and record photos as well as video, for post-processing or post-inspection review, and a camera that offers additional software features such as multiple spot temperature gauges, including the ability to control temperature rise within specific ranges
• One with an ergonomic gun trigger that makes it easy to operate a camera with one hand, as opposed to a touchscreen device that often requires two hands to operate. Sometimes these are difficult or impossible to use with heavy gloves on.

About FLIR systems

FLIR Systems was founded in 1978 in Tigard, Oregon, as a pioneer in the development of high-quality, low-cost infrared (thermal) imaging systems. However, the company’s history goes back even further, to the 1950s, when Agema of Sweden (later bought by FLIR in 1998) developed the first commercial thermal cameras, mainly for inspecting power infrastructure. Those first thermal cameras were so big and heavy that they were mounted on the back of a car or truck.

Today, FLIR offers a diversified portfolio for a number of applications in the government and defense, industrial and commercial markets. Thanks to major improvements in the size, weight, power and cost of thermal imaging cameras, FLIR thermal imaging cameras can be found in cell phones to large gimbals in military or search and rescue aircraft. For more information visit www.flir.com. RT

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