Testing the air barrier or air control layer of a home has traditionally been done using artificial pressure created by a fan, commonly referred to as a blower door test. Why You Need Blower Door Testing – Northern Built The advantage of using an air pressure differential testing is twofold, we can quantify the building tightness (CFM50, ACH50 or CFM/ft² of surface area) and locate deficiencies in the air barrier. Finding the air leaks can be done by watching for fluttering drapery or spiderwebs, feeling for air leaks, using synthetic smoke created by smoke generating tools, by thermal imaging, or measuring pressure differentials between spaces inside the building enclosure using a manometer.
The drawback with using pressure differential testing methods is the requirement of having a complete and continuous (or mostly continuous) air barrier. The air barrier needs to be mostly complete to reach 50 Pascals of pressure. You can check for air leaks with lower pressures, but if you’re setting the equipment up to test, it’s nice to perform a complete test, including the air leakage rate. Another disadvantage is having to set up a blower door for testing individual assemblies, such as checking for an air leakage in a single window or door or retesting an assembly that previously failed.
I recently discovered equipment that will identify air leakage in the building enclosure without the need for a pressure differential. It is called ultrasonic air tightness testing; the process uses sound waves to identify leakage areas.
The equipment I’m using is manufactured by Coltraco, a British manufacturer of advanced ultrasonic testing equipment. They produce equipment used to monitor the watertight integrity of ships and offshore platforms, among other applications. Development of the Portascanner® Airtight and the more basic Portascanner® (which is the model I am currently using) began during COVID, when the need for testing of airtight enclosers in hospitals and other health care facilities became critical. The development of that technology found its way to the residential and commercial encloser testing market.
How the Equipment Works
Sound is a vibration or pulse in air. The vibration creates waves, how closely the waves are bunched together is known as frequency. A better definition of frequency is the number of waves passing a point per second, measured in Hertz (Hz) or kilohertz (kHz). Humans can hear between 20 and 20,000 Hz. Personally, I can’t hear much above 12,000 Hz, too many years of working without good hearing protection. (A fun website to test your hearing is 20 – 20,000 Hz Audio Sweep | Range of Human Hearing).
Because sound travels on air waves, it is possible to measure sound as it moves through holes in our building enclosure, this is the premises of the Portascanner® equipment. The tool has two main parts, a sound generator and a sound receiver. The generator produces a cone of sound at 40,000 Hz, well above human hearing. The receiver is tuned to “hear” the noise produced at that frequency. The receiver has a digital module that registers the intensity of the signal moving through a hole in the air barrier. The bigger the hole. The stronger the signal. (A basic explanation, we’ll get into more detail shortly.) A set of headphones are included with the equipment to allow you to hear the intensity of the leak without having to continuously watch the digital reading.
The test starts by placing the frequency generator on one side of the enclosure, about 15 feet from the surface being tested. If you are testing air leakage to the outside, the generator will be located either outside the structure, or it could be inside. The receiver and sensor wand are on opposite sides of the enclosure. There are three short calibration tests to perform using the receiver and wand to make sure the equipment is operating correctly, and no interference is skewing test results. Once those are complete, air leakage testing can begin. The generator is turned on and the wand is slowly moved along the surface to be tested, a few inches away but no more than a foot from the testing surface. A leak will be identified by the intensity of the noise coming from the headphones and by the scale selected on the receiver. There are two scales, one is decibels (dB) with the range being 0-75. There is also a linear scale of 0-31,775. According to the manufacturer, leaks as small as 0.002 inches (1/450th of an inch or about half the thickness of human hair) can be detected by the equipment.
The intensity of the air leakage is determined by the value of the scale. 0 dB is an airtight assembly. Decibels above 0 indicate an air leak, though the intensity of the reading is dependent on the distance and angle of the generator compared to the hole. The standard Portascanner® does not estimate the air leakage rate, or amount of air moving through the hole, but Coltraco’s more advanced Portascanner® Airtight can. You can find more information on that tool at the Coltraco website. Ultrasonic Testing | Ultrasonic Testing Equipment – Coltraco
It is possible to detect the simpler complex three-dimensional air pathways using the Portascanner®. None of the air leak detection methods I discussed earlier are accurate at finding all leaks, having a small leak start at a ceiling light fixture and end several feet way at a wall junction is very difficult to find. There is a method to help pinpoint a leak location using the portascanner®. Finding the leak with the generator on the exterior and receiver/wand on the inside of the wall assembly, then reversing the location so the generator is on the interior and the receiver/wand on the exterior could help pinpoint the start and end point of the air leak. According to the literature supplied with the tool, learning the right location and angle for the generator to be placed is key.
Applications for the Portascanner®
I think this airtightness testing tool has a few good applications. As mentioned earlier, testing before the air barrier is complete is the biggest advantage. Being able to test without disrupting the building schedule and having the ability to test a single component or assembly is another advantage. The air leak I found at the window air seal in the video I had no ideas was there, even though I had performed two blower door tests at that project. I think with a little experience and practice in using the Portascanner®, I can see the tool becoming an integral part of my energy auditing and building investigation arsenal. The tool is only available in the United States through the Source2050 website. The standard Portascanner retails for about $4,000, the more advanced Portascanner Airtight model retails for $12,000. These are expensive tools, but unique in their abilities. Coltraco Ultrasonics Portascanner® | Source 2050