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Imagine trying to plan a dinner party, but not knowing how many guests will arrive. It would be impossible to prepare for. This is the daily challenge faced by facilities managers implementing demand control ventilation (DCV) without access to real-time occupant-count (RTO) data.

Demand control ventilation optimizes HVAC usage for energy efficiency based on a building’s current air quality and temperature needs. But older approaches to DCV usually rely on CO₂ sensors—which lack the granularity of data needed for optimum efficiency.

“CO₂-based systems can determine when a space is in ‘occupied mode,’ meaning that someone is in the room, but they don’t have access to real-time occupant count data,” explains David Whalley, co-founder and CEO of Feedback Solutions, an energy efficiency specialist that offers occupant count-based DCV solutions. “Because of this, they’re forced to default to a level of ventilation that approaches 100% of system capacity, even if there are only a handful of people present. For example, we have worked with clients with office areas built for 4,000 employees that at times have occupant levels dip to below 300 people.”

This kind of over-ventilation is costly. But it also hampers greenhouse gas (GHG) reduction efforts at universities, government facilities, commercial office buildings, and other large-scale venues where sustainability is a high priority—and in many cases, a compliance requirement.

But now flexible edge computing platforms enable occupant count-based demand control ventilation solutions. Far more effective than older systems that use CO₂ sensors, occupant count-based DCV is already achieving impressive real-world results. The increased energy efficiency is a result of the decreased kWh required by the ventilation fans along with thermal savings driven by the reduced amount of outside air required to be heated or cooled.

Realizing Green Building Benefits

Case in point is Feedback Solutions deployment with the New York State Energy Research and Development Authority (NYSERDA) at New York University (NYU).

Globally, building operations account for 28% of GHG emissions, but in New York, where extremes of temperature and older facilities are common, that number is even higher. Both the State of New York and NYU’s leadership were understandably concerned about energy efficiency on campus.

Far more effective than older systems that use CO₂ sensors, occupant count-based DCV is achieving impressive real-world results. Feedback Solutions via @insightdottech

Working with NYU, Feedback Solutions engineers installed an occupant count-based DCV system in the College of Dentistry at the Washington Square campus in Manhattan. People-counting sensors monitored the exact occupant counts of lecture halls and other large rooms in real time, with the data processed at the edge using Feedback Solutions software running on an Intel device. The resulting information was then sent to the university’s building management system (BMS) via the Building Automation Control Network (BACnet) protocol so the level of ventilation could be adjusted automatically based on actual current demand.

This resulted in a significantly more efficient HVAC strategy compared to the previous solution, which required ventilation equipment to run at more than 80% capacity when the system was in occupied mode. The new occupant count-based DCV solution was able to maintain air quality and temperature set points in lightly used rooms or rooms with fluctuating occupant levels at as little as an average of 30-40% capacity, resulting in an overall GHG emission reduction of 18%. Feedback’s system enables ventilation rates to go up and down with the population of an HVAC zone automatically in the background without manual intervention.

The university was so pleased with the results that it rolled out the technology to 15 other buildings on campus—a decision made even easier by financial incentives the new solution delivered. Beyond direct OPEX savings, NYU also offset penalties related to New York Local Law 97, a municipal sustainable-building mandate. In addition, the university was able to reduce its payback period on its investment by taking advantage of the incentive programs implemented by local power companies.

“Local utility providers in New York and many other sustainability-focused regions offer some extremely generous green-building incentives,” says Whalley. “Those incentives can cut an already fast three-year payback in half.”

Future-Proofing Sustainable Buildings

Ability to convert aging infrastructure into something greener attracts large organizations and governments around the world. It’s also of great interest to utility providers that need to find ways to reduce the load on existing building stock to enable electrification of new construction.

But a major stumbling block when undertaking retrofits is that each facility will have its own existing BMS solution—as well as its unique needs and concerns. To address this challenge, solutions providers turn to flexible designs that can be adapted to different kinds of buildings.

Feedback Solutions, for example, offers a sensor- and BMS-agnostic software platform. If an end user has unique sensor requirements, or runs multiple BMS solutions in its IT environment, it’s still straightforward to help the building operator and energy team implement a DCV system that will suit their needs (Figure 1).

The company’s technology partnership with Intel has played an integral role in developing such a versatile DCV platform.

“The Intel edge device we use is powerful and highly flexible,” says Whalley. “It allows us to offer many different configurations for our end users, from architectures that send all usage data to the cloud to solutions that are entirely on-premises.”

Creating a Holistic Data Analytics Strategy

Occupant count-based DCV systems are crucial in their own right. But access to real-time occupant data from buildings has far-reaching implications, making these solutions part of a much larger story.

When organizations know how their spaces are being used, tremendous value can be unlocked. Offices and universities can rationalize their post-Covid real estate footprints. Facility management teams can schedule more effectively, reducing operating hours at underused buildings and allocating cleaning and maintenance staff more logically. In the long term, it’s possible to make data-driven decisions about repurposing or consolidating buildings based on actual usage patterns.

This isn’t just a case of adding value in disparate areas. When building occupancy data is treated as a common fabric, it enables an integrated approach to solving some of the toughest problems of the coming decades.

“By breaking down data silos, it’s going to be possible to implement far more sophisticated optimization strategies,” says Whalley. “We see ourselves as part of a future in which the world meets its energy efficiency, space utilization, and sustainability challenges through holistic solutions.”

This article was edited by Christina Cardoza, Editorial Director for insight.tech.