Daniel Dobrowolski and John Knapp joined us recently for our Weekly Wednesday Free CEU webinar Series.
If you missed this session, want to rewatch it, or share it with a friend or colleague, you can now do so, as the recording and article on the topic are available below.
Overall, respondents reported that they primarily learned about ultrasonic technology as a new and highly accurate method for detecting, localizing, and even quantifying air leakage in buildings, often comparing it favorably with traditional blower door and thermal imaging methods. Many were previously unaware this technology existed and were impressed by its ability to find leaks earlier in construction, in specific locations, or in situations where blower door testing is difficult or invasive. Participants also noted practical insights such as how the equipment works (sound turbulence detection, directional sensing), applications to ducts and envelopes, and its potential as a complementary tool rather than a full replacement for blower doors. The main questions and uncertainties that remain center on cost and accessibility of the equipment, how it compares in accuracy and use cases to blower door testing, approval or adoption by standards bodies like RESNET/BPI, practical limitations (e.g., whole-building pressurization), and future adoption in the industry.
Article Based on Webinar*
Air leakage remains one of the most significant challenges in achieving high-performance building envelopes. Uncontrolled air infiltration and exfiltration affect energy efficiency, indoor air quality, moisture control, durability, and occupant comfort. Traditional diagnostic tools—such as blower door testing, smoke pencils, and thermography—provide valuable data but often struggle to precisely locate leaks or to operate effectively during all phases of construction. Recent developments in ultrasonic testing technology offer a new approach to detecting and quantifying building air leakage. By using ultrasonic sound transmission and detection, this method enables rapid identification of leakage pathways, quantification of leak size, and evaluation of airtightness performance across construction phases. Research conducted in controlled laboratories, university test facilities, and real-world buildings demonstrates that ultrasonic detection can locate extremely small leaks with high accuracy while providing actionable information for builders and consultants. This article examines the principles behind ultrasonic air leakage detection, compares it with traditional diagnostic methods, and explores how the technology can improve construction quality, reduce remediation costs, and support the development of high-performance buildings.
The Critical Role of Airtightness in High-Performance Construction
Airtightness has become a foundational principle in modern high-performance construction. Buildings designed to minimize uncontrolled air movement deliver substantial benefits across multiple dimensions of performance. Reduced air leakage lowers heating and cooling loads, which in turn decreases energy consumption and operational carbon emissions. A tighter envelope also enables designers to control how air enters and exits the building, allowing ventilation systems to provide filtered and conditioned air rather than relying on uncontrolled infiltration.
Beyond energy performance, airtight construction improves indoor environmental quality. When uncontrolled leakage pathways are eliminated, airborne pollutants, outdoor contaminants, and moisture are less likely to enter the building envelope. This contributes to healthier indoor air and improved durability of building assemblies. Airtight construction can also reduce unwanted noise infiltration and prevent pests from entering through envelope gaps.
These benefits have made airtightness a central requirement in many high-performance building standards. Programs such as Passive House, ENERGY STAR, and other performance frameworks rely on airtight envelopes as a fundamental strategy for achieving efficiency targets and improving occupant health. Achieving those targets, however, requires reliable methods to detect and correct air leakage.
Limitations of Traditional Air Leakage Diagnostics
Several diagnostic methods are commonly used to evaluate airtightness. The most widely recognized is the blower door test, which pressurizes or depressurizes a building and measures the rate of air leakage through the envelope. The test provides an overall performance metric, typically expressed as air changes per hour at a defined pressure differential.
While blower door testing provides valuable data about the total leakage of a building, it does not identify where leaks occur. The test can confirm that a building is failing to meet an airtightness target but offers little guidance on the exact location or severity of individual leakage pathways.
To locate leaks, practitioners often rely on supplementary techniques. Smoke pencils can reveal airflow patterns by showing where smoke is drawn toward leakage points. Anemometers can measure air velocity through known openings. Thermal imaging cameras may reveal cold or warm spots caused by air infiltration when sufficient temperature differences exist between interior and exterior environments.
Each of these tools has limitations. Smoke tests require pressurization and can be difficult to use in large or complex buildings. Anemometers are useful only when the location of a leak is already known. Thermography depends on temperature differences that may not be present during construction or mild weather conditions.
These constraints make it difficult to locate leaks during key stages of construction—particularly before the building envelope is fully sealed or before interior finishes are installed. As a result, problems often remain hidden until late in the project, when remediation becomes costly and disruptive.
The Concept Behind Ultrasonic Air Leakage Detection
Ultrasonic testing offers an alternative approach to identifying air leakage. The technique relies on transmitting high-frequency sound waves and detecting whether those waves pass through the building envelope. Because ultrasonic frequencies travel through even extremely small openings, they provide a sensitive method for identifying leakage paths.
The system operates through a simple but powerful principle. A generator placed outside the building emits ultrasonic sound waves that blanket the exterior envelope. Inside the building, a handheld detector listens for any ultrasonic signal that penetrates through the structure. If ultrasound is detected inside the building, it indicates that a pathway exists through which air can travel.
In practice, the equipment consists of two primary components: an ultrasonic transmitter and a sensor connected to a handheld scanning device. The transmitter emits high-frequency sound waves that are inaudible to humans. The handheld sensor scans building surfaces to detect ultrasonic signals that pass through cracks, joints, penetrations, or other discontinuities in the air barrier.
This method enables users to rapidly scan walls, windows, doors, and other building elements to determine whether leakage pathways exist. Because ultrasound travels through very small openings, the technique can detect leaks that may be invisible or difficult to identify using conventional methods.
From Leak Detection to Quantification
One of the most significant advantages of ultrasonic testing is its ability not only to detect leaks but also to quantify them. The technology measures the strength of the ultrasonic signal passing through a gap and uses algorithms to estimate the size of the opening and the airflow associated with it.
The detection device displays this information through a visual interface that indicates the intensity of the signal. As the sensor approaches a leakage point, the signal increases, allowing the user to pinpoint the exact location of the opening. This process resembles the operation of a metal detector, in which signal strength guides the user toward the target.
Once a leak is identified, the device can estimate the cross-sectional area of the opening and calculate the associated airflow rate when provided with the relevant pressure differential. These measurements allow practitioners to determine which leakage points contribute most significantly to overall air infiltration.
By aggregating measurements across multiple locations, it becomes possible to estimate the building’s overall air leakage performance. In effect, the system can simulate an airtightness metric similar to the one obtained from a blower door test.
Research and Validation of Ultrasonic Airtightness Testing
Research conducted in collaboration with university laboratories has provided important validation of ultrasonic testing methods. In controlled experiments, researchers created leakage openings of known sizes and compared ultrasonic measurements with conventional testing approaches.
The results showed that ultrasonic detection could accurately measure leakage areas with a high degree of precision. In controlled laboratory conditions, measurements consistently fell within approximately ten percent of the actual leak size. Even extremely small openings—down to fractions of a millimeter—could be detected and measured.
Additional research was conducted in partially controlled environments such as full-scale test houses built within university research facilities. In these experiments, ultrasonic measurements were compared with blower door testing and thermographic imaging.
The studies showed that ultrasonic detection successfully identified the same direct leakage points that were detected through other methods, including gaps around doors, vents, and other envelope penetrations. In addition, ultrasonic testing provided quantitative information about airflow through each leak—data that thermography could not provide.
Thermal imaging often revealed patterns that were difficult to interpret because temperature differences could arise from both air leakage and thermal bridging. Ultrasonic detection avoided this ambiguity by responding only to actual openings that allowed sound—and therefore air—to pass through.
Applications in Real Buildings
Field testing in real buildings has demonstrated the versatility of ultrasonic technology. The method has been applied to new construction, retrofits, modular building manufacturing, and existing structures undergoing performance improvements.
In large buildings under construction, ultrasonic testing has proven particularly valuable for evaluating airtightness before interior finishes are installed. Builders can scan the envelope at multiple stages of construction and identify problems early, when repairs are easier and less expensive.
In retrofits, the technology helps identify hidden leakage pathways that may have developed over time. Buildings that were originally constructed to high airtightness standards can experience performance degradation as components age or as modifications are made to electrical, plumbing, or mechanical systems.
Ultrasonic testing has also been used to diagnose unexpected leakage caused by installation errors. For example, small obstructions near seals or gaskets can compromise airtightness even when the problem is not visually apparent. In such cases, ultrasonic detection can reveal the presence of air leakage that would otherwise remain hidden.
Another practical application involves duct systems. By placing the ultrasonic transmitter inside ductwork and scanning the exterior of the ducts, technicians can detect leaks that may reduce the efficiency of heating and cooling systems.
Integration into the Construction Process
One of the most powerful advantages of ultrasonic testing is its ability to be used repeatedly throughout the construction process. Because the equipment requires minimal setup and does not depend on pressurizing the building, it can be deployed quickly at multiple stages of construction.
Builders can perform rapid scans after major milestones, such as the installation of windows, mechanical penetrations, or air barrier membranes. If leaks are detected, repairs can be made immediately before the building assembly is concealed behind insulation or drywall.
This approach contrasts sharply with the traditional model in which airtightness is evaluated only once, near the end of construction. When a blower door test reveals a problem at that stage, locating the cause can require extensive investigation and sometimes destructive work.
By identifying leaks earlier, ultrasonic testing reduces the likelihood of costly remediation cycles. In some documented projects, multiple rounds of repairs were required before a building finally met airtightness targets. Early detection could have prevented those delays and expenses.
Expanding Use Across the Building Industry
The technology is increasingly being used across a range of industry applications. Manufacturers of modular buildings have integrated ultrasonic testing into factory quality assurance processes, scanning building modules before they leave the production line. Window manufacturers have adopted the method to verify the airtightness of glazing assemblies.
Contractors and consultants use ultrasonic detection to verify the quality of installations, particularly around mechanical penetrations and complex junctions. By providing clear visual and quantitative evidence of leakage, the technology facilitates collaboration between designers, builders, and subcontractors.
For building performance professionals, ultrasonic testing offers a valuable diagnostic tool when evaluating existing buildings. Instead of relying on assumptions about common problem areas, practitioners can directly observe where leakage occurs and prioritize remediation efforts accordingly.
Toward More Reliable Airtight Construction
Achieving reliable airtightness requires more than meeting a single performance test at the end of construction. It requires a systematic approach that identifies potential problems early and verifies that corrective measures are effective.
Ultrasonic testing represents an important advancement in the toolkit available to building professionals. By enabling rapid, precise detection of air leakage pathways, the technology supports a proactive approach to airtightness management.
When used alongside established methods such as blower door testing, ultrasonic diagnostics can help ensure that buildings meet performance targets while avoiding costly delays and rework. As high-performance construction becomes more widespread, tools that improve accuracy, efficiency, and transparency will play an increasingly important role.
Educational resources and training on emerging technologies such as ultrasonic air leakage detection are made available through organizations such as the Green Home Institute, which works to empower building professionals to create healthier and more sustainable homes.
Key Takeaways
- Airtightness is critical for energy efficiency, indoor air quality, moisture control, and building durability.
- Traditional diagnostics such as blower door tests identify overall leakage but often cannot pinpoint specific leak locations.
- Ultrasonic technology detects leaks by transmitting high-frequency sound through the building envelope and sensing where it passes through gaps.
- The method can detect extremely small leaks and estimate airflow through individual leakage pathways.
- Research shows ultrasonic detection can measure leak size with high accuracy and identify leaks that other methods may overlook.
- The technology can be used throughout construction, enabling early detection and repair before assemblies are concealed.
- Ultrasonic testing supports applications in new construction, retrofits, duct testing, modular manufacturing, and building diagnostics.
- Early leak detection can significantly reduce project delays, remediation costs, and uncertainty during airtightness testing.
*Content created by a human speaker, transcribed by Zoom, and arranged by an AI LLM
Q&A Follow Up
Q: Can you send me the powerpoint presentation, link to replay and the certificate?
A: All attendees have received a follow up email with a link to rewatch the webinar. Here is how you get your certificates: https://greenhomeinstitute.org/how-to-do-a-greenhome-institute-live-ceu-webinar-a-f-a-q/
Q: Can this instrument be used to locate leaks in ventilation ducts?
A: You can use the Portascanner® AIRTIGHT to detect leaks in ductwork, provided you have suitable access to the inside of the duct so the ultrasonic generator can be placed within the section under test. As with any ultrasonic method, coverage can be affected by the duct configuration, so in more complex runs, bends, branches, dampers, internal lining, or other obstructions may reduce how effectively the ultrasound travels through the full length of the system. In practice, this means some duct layouts may need to be tested in sections to achieve the best results.
Q: Can this instrument be used to locate leaks in ventilation ducts and can the testing done from this equipment be used as a report for LEED Homes submission by Energy Rater?
A: Outside of the US it could, but in the US and Canada you must use a blower door; for points outside of the US you need blower door for extra energy points. A LEED Interpretation would need to be submitted to determine if allowed from there.
Q: How does this affect wildlife and dogs within range of the speaker?
A: 40kHz is a frequency that can be heard by dogs and wildlife; however, the Portascanner AIRTIGHT has been used where animals are present with no apparent impact. Likewise for humans, the amplitude is well below the level that would harm anyone’s hearing.
Q: Are these leaks reported at 50 Pa ΔP, or at natural pressure differentials?
A: The Portascanner® AIRTIGHT can be configured to report for different pressure differentials simply by changing the value in the settings. The default value is 50 Pa.
Q: How specifically did you repair leaks in new door weatherstrip as shown in example?
A: I believe with sealant – (John Knapp video at Manhattan House).
Q: Does the Coltraco unit on source2050.com come with the tablet as shown in the video/presentation? Can the setup be duplicated by practitioners immediately?
A: Yes – Portascanner® AIRTIGHT package includes:
- Portascanner® AIRTIGHT Main Receiver Tablet, 1 x Ultrasound Sensor Wand with Flexible Head and 2.5m length BNC cable, 4 x Aluminium Rod Sections and 1 x Sensor Handle
- 1x Transducer Ultrasonic Generator – ideal for smaller sites such as individual apertures
- 5x Transducer Ultrasonic Generator – ideal for larger structures
- 5cm Sensor Positioning Guide, Generator Tripod Stand and Clamp, Pair of Headphones, Micro-USB Charger, USB Stick, USB WiFi Dongle, USB Splitter, Operating Manual, Calibration Certificate, Robust Carrying Case.
Q: What is the cost of this instrument and is it available in Middle East (UAE and KSA)?
A: Yes – contact via https://coltraco.com. For US and Canada queries, contact https://source2050.com/product/coltraco-ultrasonics-portascanner-airtight-520/
Q: Would like to hear about use in evaluating ceiling/roof (and tall upper floor walls) related leaks such as around recessed can lights, exhaust vents, and other penetrations in evaluating older homes undergoing energy upgrades/renovations.
A: The Portascanner® AIRTIGHT can be used in retrofit projects. The basic principle of ultrasonic leak detection is that ultrasound is blocked, absorbed, and reflected by solid boundaries, but transmits very effectively through air. This means that where there is a gap in a structure for air to pass through, ultrasound will pass through this and be emitted from the other side, even if the leak path is not straightforward.
Q: Could the unit be used to test window and door installations as they are installed, or would adjacent empty rough openings (where neighboring window/door is not yet installed) allow so much sound leakage that the test could not be valid? Or similarly, could you test a mock-up that is not completely enclosed?
A: Yes to both, the Portascanner® AIRTIGHT is ideal for this application as a complete envelope is not required. We have window and modular building manufacturers who use this to test in the factory as well as on site.
Q: I’m confused (not uncommon). We often specify CFM50 or CFM75, because we measure those directly. Getting ELA depends on subsequently applied algorithms. Some leaks in buildings are going to be accessible with the US tester without scaffolding, ladders, etc. So how does a person using US tester get a total building CFM50 without getting to every square foot or (meter) of thermal enclosure?
A:
To get the most accurate reading for the total CFM50/CFM75, you need to scan the full thermal envelope. This is where it’s probably more practical to use a Blower Door test, especially for a large building. The Portascanner® technology is designed to pinpoint where leaks are and provide information about why they matter for overall airtightness.
What you can do with the Portascanner® AIRTIGHT is find and measure some leaks, input the envelope area and desired pressure differential (e.g., 50 Pa or 75 Pa), and it will tell you the air permeability (i.e., CFM).
- You could input the total envelope area and it will tell you how significant the leaks you have found are in the context of the whole building.
- You could input only the area scanned and get an estimation of the CFM, which would be 100% accurate if the sample is representative (not always guaranteed).Blower door tests and the Portascanner® AIRTIGHT address airtightness in fundamentally different ways and serve different purposes. Blower door testing gives a single permeability value for certification, but does not identify leak locations. The Portascanner® AIRTIGHT detects, locates, and quantifies individual leak sites, helping to ensure the actual performance matches the intended design quality.
Q: When using a blower door on casement windows we typically do a positive and negative pressure test which helps understand how the windows will handle strong winds. Does your test offer anything comparable?
A: The Portascanner® AIRTIGHT is not a direct substitute for positive and negative pressure cycling as in blower door tests for wind loading. Blower door testing assesses whole-window performance under pressure differentials.
However, the Portascanner® AIRTIGHT allows you to locate and quantify precise leakage paths through the window assembly, seals, frame junctions, etc., during positive, negative, or zero pressurization. It provides a targeted diagnostic assessment of airtightness, complementing blower door testing.
Q: What does the algorithm that converts the square mm of leakage into CFM50 account for?
A: The Portascanner® AIRTIGHT uses ultrasound to measure the cross-sectional area of leaks. Flow rate is calculated using a numerical solver of the Darcy-Weisbach equation, which requires thickness, roughness, and pressure differential as user inputs. The envelope area is needed to calculate air permeability, or the volume of the space for the ACH value.
Q: John, how does the capability of the Portascanner compare to the Airtight 520 package?
A: The Portascanner will locate air leak sites but not quantify the leak rate. The Portascanner AIRTIGHT will also quantify the leak rate, can calculate ACH if required, and produces a PDF report. The former is a more basic unit with a small LCD; the latter is a touchscreen tablet device.
Q: The “project delays” cost here is curious??
A: The delay figure was meant as an indicative programme-impact cost, not a hard invoiced amount. It reflects the knock-on commercial impact of delays, for example site management time, rescheduling trades, etc. The strongest part of the case is actually the direct rework cost (labour, materials, access, repeat testing), which already comes to about £17,500. Even if we exclude delay-related impacts, the cost of reactive remediation is still significant.
Q: How repeatable is the ultrasonic testing?
A: Totally repeatable; if there is still a leak after repair, it will be found by our technology.
Q: Can these be rented? Or purchased used and sold used for limited time use like a homeowner/contractor building their own project?
A: Coltraco do not rent these instruments. However, using our technology could be a paid service to offer.
Q: Any plans to separate the hardware from the software and let the measurement device plug into a standard Android phone with an app?
A: We have variants in development.
Q: Is there any technical reason that a $100 ultrasonic leak detector kit from Amazon is far less effective than a $1000-2000 kit?
A: Many lower-cost ultrasonic leak detectors are for passive detection of leaks in already pressurized systems (e.g. HVAC, gas). They may have less controlled signal generation, no matched transmitter/receiver, and limited sensitivity and repeatability. They often lack documentation, quantified readings, or reporting. For an architect using a detector for occasional spot-checking, a low-cost unit may have some value, but a purpose-designed system provides better detection of small leaks, consistency, and evidence for commercial or technical needs.
Q: How close to the receiver does the sound generator need to be positioned? Does the generator need to be moved frequently during testing a building? Do you usually have a worker positioned at the generator to keep it moving along with a second person with the receiver?
A: Approximately 2 inches/5cm from the structure. The generator covers a large area but will likely need repositioning when testing. This is easier with a second person but can be managed by one if necessary.
Q: In practice it seems like pressurizing an enclosure and utilizing cinematic smoke to visualize/physically see leakage would be a more effective method overall but this would be a great tool if it became more affordable.
A: The Portascanner® AIRTIGHT produces a PDF report showing air leak sites and leak rate. This is tangible evidence for clients and useful where a third party will be carrying out remediation.
Q: How do you handle testing on upper floors?
A: Scaffolding, telescopic pole, or drone as discussed.
Q: Great long chat, really hope you get to the price question.
A: Price on application via Coltraco or Source 2050.
Q: How could you test ducts using this device?
A: You can use the Portascanner AIRTIGHT to detect leaks in ductwork, provided you have suitable access to the inside of the duct so the ultrasonic generator can be placed within the section under test. The ultrasound floods the interior of the duct and the exterior can then be scanned with the wand. In complex configurations, testing may need to be done in sections for best results.
Q: John’s response makes me think we still need a blower door to get a CFM50/CFM75 number
A: The Portascanner® AIRTIGHT complements the blower door test, which is mandatory.
Q: What would be the cost for a basic device with a generator and a mic for applications which don’t need a quantified result for say $100?
A: Entry point Portascanner is an option. Our products are manufactured in the UK to a high standard of accuracy and longevity; cheap is very rarely best.
Q: How does ultrasound work in detecting leak sites with the Portascanner® AIRTIGHT?
A: The Portascanner® AIRTIGHT uses an ultrasonic transmitter to generate a controlled signal on one side of the construction or enclosure being tested. If the surface is airtight, the signal remains contained. If there is a gap or leakage path, the ultrasound passes through it. The handheld receiver on the other side detects this escaping signal, allowing the user to identify and accurately locate the leak site.
Q: How does ultrasonic integrity testing fit in with blower door testing?
A: Blower door tests and the Portascanner® AIRTIGHT serve different, complementary purposes. Blower door tests provide a single permeability value for certification by pressurising a building, but do not identify leak locations. The Portascanner® AIRTIGHT detects, locates, and quantifies individual leak sites, helping to ensure the actual performance matches the intended design quality. The methods are complementary.
Q: What is the scope of ultrasonic integrity testing?
A: Ultrasonic integrity testing is suitable across a range of applications where it is important to identify leakage paths and verify the integrity of sealed constructions or components. Typical uses include:
- During construction or retrofit, before the building envelope is fully completed;
- Towards project completion, before, during, or after an air pressurisation test;
- On specialized components or controlled environments where airtightness or watertightness is critical.
Its application depends on access: generally the generator must be placed on one side of the test area and the receiver on the other.
Q: Can ultrasonic integrity testing be a good solution to finding tiny leaks in waterproofing membranes prior to insulation installation?
A: Yes, ultrasonic integrity testing can be very effective for identifying very small leaks in waterproofing membranes before insulation or other coverings are installed. The key requirement is access to both sides of the area under test.
Q: Can ultrasonic integrity testing be a good solution for the identification, quantification and therefore prioritisation on leaks on difficult to reach apertures such as on high-rise buildings?
A: Yes, provided there is practical means of accessing both sides of the test area. The main consideration is generator placement, which can be achieved by scaffolding, suspended access, façade access systems, cradles, MEWPs, or extension arms. Testing can be planned in sections to suit access.
Q: Which Portascanner® ultrasonic generator is right for my application? And how do I properly place it for the best results?
A: For smaller structures, use the single-transducer generator. For larger structures, use the five-transducer generator for broader coverage. For leak quantification, the single-transducer is generally preferred for a more stable signal. For larger structures where leak quantification is important, use both generators. Adjust the angle of the generator to follow the most effective path through any openings.
Q: Can this be useful for museum display cases?
A: Yes, ultrasonic integrity testing can be very useful for museum display cases, allowing leakage paths to be identified consistently without gaseous tracers. This is useful for comparing performance in different environments and for ongoing monitoring.
Q: Is the ultrasound harmful to hearing after long exposure and will it affect dogs and wildlife?
A: The Portascanner® AIRTIGHT is designed for professional use, and there is no evidence its ultrasound output causes harm to human hearing, pets, or wildlife in normal operating conditions.
Q: What standards (if any) do ultrasonic integrity testing instruments such as the Portascanner® AIRTIGHT comply with?
A: The Portascanner® AIRTIGHT is a diagnostic instrument designed for airtightness investigations and to assist users in meeting performance targets. It should not be regarded as a direct substitute for jurisdiction-specific whole-building airtightness tests where formal pressurisation is required. It complements regulatory testing by helping ensure the actual performance matches intended design quality.
Q: Can this catch/measure air integrity leaks in multi-layer walls?
A: Yes, provided there is an unobstructed path through the structure. Ultrasound can travel further in confined spaces. As long as one end of the leak is within the coverage area of the generator, the receiving wand can be scanned over a wider area to locate the exit point.
