This webinar from LONG’s partners at Critical Room Control examined the role of accurate airflow measurement in maintaining building health, indoor air quality (IAQ), and proper pressurization in commercial buildings. The session focused on how understanding and measuring airflow enables better control of ventilation, pressure relationships, and energy performance across a wide range of commercial applications.
The presentation began by establishing the connection between indoor air quality and building health. Modern occupants spend a large portion of their time inside buildings (like offices, retail spaces, and other commercial environments), making IAQ a critical factor in occupant comfort, productivity, and health. Poor IAQ is often associated with what is broadly referred to as “sick building syndrome,” which can stem from inadequate ventilation, indoor air pollutants, and improper air distribution. These issues are especially pronounced in workplaces, where occupants may spend 40 to 60 hours per week in the same indoor environment.
A recurring theme throughout the webinar was that airflow awareness is foundational to good IAQ. Without reliable data on how much air is moving through a building and where it is going, it becomes difficult to ensure pollutants are removed, fresh air is delivered appropriately, and pressure relationships are maintained as designed.
The webinar used seasonal building behavior as a practical example of why airflow measurement matters. Buildings experience different pressure dynamics throughout the year due to stack effect, which varies between heating and cooling seasons. In winter, lower floors of a building often become negatively pressurized, drawing cold outdoor air inward. As this air warms, it rises and migrates toward upper floors. In summer, the effect can reverse, with warmer air entering higher levels and sinking as it cools.
These seasonal pressure shifts can lead to uncontrolled infiltration and exfiltration, causing comfort issues, moisture problems, and increased energy use. Measuring airflow helps facility teams identify whether a building is operating near neutral pressure, slightly positive pressure, or unintentionally negative. Maintaining proper pressure balance is critical to preventing air from entering wall cavities, interstitial spaces, or other unintended pathways that can trap contaminants or moisture.
Ventilation rate is another major consideration. Over‑ventilating a space can be just as problematic as under‑ventilating, increasing energy consumption without necessarily improving air quality. Accurate airflow measurement allows operators to verify that ventilation rates meet—but do not exceed—design requirements and applicable standards.
At the core of the webinar was CRC’s use of passive indirect airflow sensing technology. This approach differs from traditional airflow measurement devices that rely on active probes, thermal sensors, or flow‑through pressure ports placed directly in the airstream. Passive indirect sensing places no active components in the airflow, making the measurement inherently resistant to contamination and particulate buildup. Because nothing protrudes into or draws air from the airstream, the technology is unaffected by dust, debris, or airborne contaminants. This eliminates common issues such as sensor drift, fouling, and the need for routine cleaning or recalibration. As a result, airflow readings remain stable over time unless actual flow conditions change.
The technology is based on an airfoil design. As air passes over the airfoil, it splits and accelerates across the top surface while moving more slowly along the bottom. This creates a static pressure differential. Using Bernoulli’s principle, the system translates that pressure difference into an accurate airflow measurement. Because the measurement depends on pressure deflection rather than direct contact with airflow, the system does not require long, straight duct runs or fully developed flow conditions, providing greater installation flexibility. The pressure differential is measured using dead‑ended transducer technology, meaning there is no airflow through the sensor itself. This further prevents particulate entrainment and eliminates another common source of maintenance issues found in traditional airflow measurement devices.
CRC’s airflow measurement solution is built around the Airflow Wing (AFW) combined with a dedicated transmitter. This system provides high accuracy and repeatability without the maintenance burden typically associated with airflow sensors. The transmitter can support multiple airflow stations, allowing a single device to measure several independent airstreams. A common application described in the webinar is a mechanical system that includes outside air, return air, and exhaust air. Instead of installing separate transmitters for each airstream, multiple airflow wings can be connected to a single transmitter, simplifying system architecture while preserving independent airflow measurements. The technology is particularly well suited for outside air measurement, where contaminants, moisture, and debris are common. Installation near louvers, hoods, and dampers is often challenging with traditional airflow sensors, but the passive indirect design allows reliable measurement with relatively short straight‑duct requirements, such as six inches between dampers and airflow stations.
As duct sizes increase, additional airfoil probes can be installed to ensure accurate capture of airflow across the entire duct cross‑section. Larger openings may require multiple probes arranged to provide representative measurements. The system can be mounted horizontally or vertically with no loss of performance, accommodating a wide range of duct configurations.
One significant advantage highlighted was the ability to mount the airflow wings perpendicular to damper blades, which is especially useful when measuring airflow near outside air dampers. This simplifies installation and improves measurement stability, even in turbulent or non‑ideal airflow conditions.
Additionally, the webinar addressed airflow measurement in systems with fan arrays, which are increasingly common in modern air handling units. CRC’s XF5 solution allows airflow measurement across multiple fans (up to twelve fans across two arrays) and provides totalized airflow values. This enables operators to track total supply and return airflow, as well as integrate outside air measurements, all through a single transmitter. Airflow wings can be mounted on the face of fans using standoff hardware to avoid interfering with fan performance or inlet bells. The technology can also be mounted upstream of backdraft dampers, measuring airflow only when dampers are open, which adds flexibility in retrofit and factory‑built systems.
The webinar concluded by emphasizing the operational benefits of accurate airflow measurement: reduced maintenance, wide sensing range, and installation flexibility. The system can measure very low velocities—below 100 feet per minute for outside air—as well as high velocities up to 5,000 feet per minute. Because the technology is unaffected by temperature, moisture, or particulate contamination, it is well suited for long‑term use in commercial buildings.
Overall, the session reinforced that intelligent airflow measurement is a critical tool for maintaining indoor air quality, managing building pressurization, and ensuring that air moves through a building as designed.