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For more than two decades, design engineers have tried—and largely failed—to use occupancy data to right-size ventilation. At NexusCon, John Vilani, a consulting engineer at Grumman/Butkus, explained why those efforts kept falling short, and why he believes today’s IoT occupancy systems are different enough to finally matter.
Vilani traced the first wave back to post-9/11 Manhattan, when access control systems proliferated across office towers. In theory, badge swipes offered real-time headcounts. In practice, they never made it into HVAC control. “I stand here today saying I’ve really never been successful ever in getting the data out of the security system,” Vilani said. “Never once.”
The second wave—CO₂-based demand-controlled ventilation—delivered incremental gains but failed operationally in transient spaces. “You finally get the conference room up to a thousand parts per million,” Vilani said, “and now we actually get ventilation.” By then, the space was already over-occupied and uncomfortable. CO₂ signals reacted too slowly and couldn’t support occupied/standby logic.
What changed, Vilani argued, isn’t control theory—it’s data usability. Wireless people-counting sensors now deliver continuous, zone-level occupancy signals that controls teams can actually integrate. “We’re actually getting much more scientific in how we’re doing advanced outside air control,” he said, describing how airflow stations and occupancy math replaced blunt CO₂ thresholds.
That shift reframes DCV’s history. The limitation wasn’t bad algorithms; it was fragmented systems, blocked integrations, and unusable data. New ASHRAE and IECC provisions around occupied and standby modes now make that data operationally valuable—but only if engineers are willing to work deep in the weeds of zones, boxes, and recovery rates. “There’s still some art to the science,” Vilani said.
If you’d like to learn more, here are some ways to stay updated on stories like this:
For more than two decades, design engineers have tried—and largely failed—to use occupancy data to right-size ventilation. At NexusCon, John Vilani, a consulting engineer at Grumman/Butkus, explained why those efforts kept falling short, and why he believes today’s IoT occupancy systems are different enough to finally matter.
Vilani traced the first wave back to post-9/11 Manhattan, when access control systems proliferated across office towers. In theory, badge swipes offered real-time headcounts. In practice, they never made it into HVAC control. “I stand here today saying I’ve really never been successful ever in getting the data out of the security system,” Vilani said. “Never once.”
The second wave—CO₂-based demand-controlled ventilation—delivered incremental gains but failed operationally in transient spaces. “You finally get the conference room up to a thousand parts per million,” Vilani said, “and now we actually get ventilation.” By then, the space was already over-occupied and uncomfortable. CO₂ signals reacted too slowly and couldn’t support occupied/standby logic.
What changed, Vilani argued, isn’t control theory—it’s data usability. Wireless people-counting sensors now deliver continuous, zone-level occupancy signals that controls teams can actually integrate. “We’re actually getting much more scientific in how we’re doing advanced outside air control,” he said, describing how airflow stations and occupancy math replaced blunt CO₂ thresholds.
That shift reframes DCV’s history. The limitation wasn’t bad algorithms; it was fragmented systems, blocked integrations, and unusable data. New ASHRAE and IECC provisions around occupied and standby modes now make that data operationally valuable—but only if engineers are willing to work deep in the weeds of zones, boxes, and recovery rates. “There’s still some art to the science,” Vilani said.
If you’d like to learn more, here are some ways to stay updated on stories like this:
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This is a great piece!
I agree.