How MEMS Gauge Pressure Sensors Can Reduce VAV Controller Costs

In modern building design, energy efficiency and occupant comfort are top priorities. One technology that plays a critical role in achieving both is the Variable Air Volume (VAV) system. Commonly used in commercial buildings, VAV systems offer a smarter, more flexible alternative to traditional HVAC setups, providing improved zone-level control and significant energy savings.

How VAV Systems Use Pressure Sensors

Each VAV box serves a specific zone in the building. A thermostat in that zone monitors temperature and adjusts a damper inside the VAV box to increase or decrease airflow as needed to reach the target setpoint. The airflow is measured using a differential pressure sensor housed in the VAV controller, which is connected to a pitot tube via flexible vinyl or polyethylene tubing.

Why Differential Pressure Sensors Drive Up Cost

However, differential pressure sensors are among the more expensive components in a VAV controller. One reason is the physical robustness required: to accommodate two ¼-inch outer-diameter tubes, the sensor ports must be strong enough to endure insertion forces as well as the stress of being carried or pulled by the tubing during handling and installation. These mechanical requirements demand a more rugged sensor housing, increasing both size and cost.

To mitigate this, some VAV controller manufacturers use smaller, lower-cost differential pressure sensors paired with barb adapters. While this reduces the sensor size, it doesn’t fully address the cost and complexity.

The Case for Gauge Pressure Sensors in VAV Applications

A more innovative and cost-effective solution is to use a compact, low-cost gauge pressure sensor integrated directly into the VAV controller housing. Gauge pressure sensors are inherently less expensive than two-port differential pressure sensors. Additionally, integrating barb fittings into the controller cover can be done at virtually no added cost beyond initial tooling.

How It Works: A Simpler, Integrated Design

The image above illustrates how a gauge pressure sensor can be integrated into a VAV controller cover. Because a gauge sensor is essentially a differential sensor with only one port, the same pressure differential can be achieved by reflowing a gauge pressure sensor onto a daughter PCB while sealing it around one barb fitting and sealing the PCB itself to the VAV controller housing. An SMD spring connector could be utilized to make electrical contact with the sensor via the electrical pads on the backside of the daughter board. This configuration meets the demanding mechanical and environmental requirements of typical VAV applications while reducing costs.

Conclusion: A Smarter Path Forward

By replacing traditional differential pressure sensors with compact gauge pressure sensors, VAV controller manufacturers can significantly reduce component costs and simplify assembly without compromising performance. As HVAC systems continue to evolve for smarter building management, innovations like MEMS-based gauge sensors offer a path toward more efficient, affordable, and scalable solutions in commercial climate control.