What is thermography and why is it interesting?
First of all, themography or thermal graphic imaging is when the heat of an object or objects is detected by a thermal imaging camera and displayed as an image or video. A special type of camera commonly called a “thermal camera” or “thermal imaging camera” is necessary to capture or display a thermal image.
Thermal graphic images are interesting because the temperature of an object or objects within the frame are displayed and often measured within the image. Images can tell you a great deal about the object that is undetectable by the human eye. Be careful though, thermal imaging cameras are not point and shoot devices. Materials of different kinds reflect heat in unique ways. For this reason it’s important that the person operating the thermal camera have some training and background in the field.
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Cool!! But how is thermal imaging possible?
Everything in nature that exists above the temperature of absolute zero (-273.15°C, 0°K or −459.67°F) emits radiation in the infrared range of the electromagnetic spectrum. In other words, anything that has heat emits a form of light at a frequency related to the temperature of that object. Different temperatures appear in a thermal image in the same way that colors appear differently in a photograph.
One can imagine the human eye as a thermal imaging camera. What we call visible light is simply the average temperatures that are produced by our sun and captured by your eyes. Our brains interpret the sun’s heat radiation as the colors of the spectrum (red, orange, yellow, green, blue, indigo, violet). Our eyes evolved to detect the reflection of colors from objects within a specific range of the electromagnetic spectrum.
We can see these colors due to our daytime activity in the same way that a cat can see at night to accommodate night hunting. Different creatures evolved the ability to detect electromagnetic radiation (light,infrared) as well as vibration (sound) at different wavelengths. A thermal imaging camera is essentially a tool for extending our vision into the detection of energy emanated at a much lower temperature.
Thermal imaging cameras are designed and built to detect the temperatures that humans would be most likely to measure. There are different cameras for different applications, but most cameras detect the infrared range of roughly 9,000–14,000 nanometers or 9–14 µm. By detecting and displaying this information they produce images of that radiation, called thermograms. These are more commonly called “thermal images.”
Why is Thermography useful?
In construction, thermography is incredibly useful because it can quickly and easily demonstrate flaws in a construction assembly. These flaws are commonly seen as cold or hot spots which indicate a lack of insulation in a particular location. They can also show the location of invading insects or potentially where water damage has occurred.
When commissioning a building or piece of equipment, thermography is very useful for determining proper operation of the wall assembly or equipment.
When designing a building, an understanding of heat flow through construction assemblies is amplified by an understanding of thermography. If you have seen or can envision the assembly in the manner in which a thermal camera would, it makes designing for energy efficiency much simpler.
While conducting an energy audit thermal imaging can show problem areas and places to fix first. You could think of thermal imaging as a tool to discover the low hanging fruit of energy efficiency. I’ve included a few images to demonstrate what a thermal camera is useful for.
Thermography demonstrates Thermal Bridging
Thermal images can also demonstrate the concept of “thermal bridging.” Thermal bridging is where materials of a construction assembly conduct heat at different rates due to their composition. Wooden studs and metal beams are common thermal bridges that can waste significant energy in buildings. Many people in construction fail to pay attention to thermal bridging even though eliminating thermal bridging is key to an energy efficient building envelope.
For instance did you know that wooden studs conduct heat 3 times as well as the cheapest and most common form of insulation, namely fiberglass batts? For less thermally conductive insulation types such as spray foam, wood conducts up to 7 times as well. Metal based construction sees even more energy loss due to thermal bridging because metal conducts heat much better than wood.
Thermal bridging is not something that most can picture without seeing it first hand. This is why I shot this creative video to demonstrate thermal bridging.
How can Thermography help me save money?
If you don’t have a target to shoot for, it’s difficult to aim. When it comes to solving issues related to energy efficiency, thermal graphic imaging is a quick and easy way to spot your best targets. These are the low hanging fruit and often the best opportunities for improvement.
If you are experiencing drafts or cold areas within your home or building, thermography can definitely assist with detecting problems. When performing an energy audit, it is recommended that thermography is utilized by someone who has been trained to interpret thermal images.
Shane Wolffe P.Eng, LEED AP BD+C, CEA, Level 1 Thermographer
Did you learn something new by reading this? Do you have any questions? Leave a comment and let me know.