Sontay Bridge and wireless CO₂ & occupancy sensing help reduce fan power by 97.6% across seven university lecture theatres.

The challenge

A UK university wanted to improve the energy efficiency of ventilation across seven lecture theatres without compromising indoor air quality or student comfort.

Lecture theatres can experience significant changes in occupancy throughout the day. A room may go from being fully occupied during a lecture to only having a handful of students inside, or being completely empty, within a matter of hours.

However, the existing ventilation system operated to fixed schedules rather than responding to how the spaces were actually being used. This meant air handling units (AHUs) could continue operating unnecessarily during unoccupied periods, wasting fan, heating and cooling energy.

At the same time, simply reducing ventilation was not an option. When lecture theatres are busy, adequate ventilation is essential for maintaining good indoor air quality and providing a comfortable learning environment where students can concentrate and remain focused.

The university therefore needed a solution that could:

  • Identify when lecture theatres were genuinely occupied

  • Monitor CO₂ levels continuously

  • Automatically adjust ventilation according to demand

  • Reduce unnecessary fan, heating and cooling energy

  • Integrate with the existing Building Management System (BMS)

  • Be installed with minimal disruption to the active university environment

The solution

In May 2026, Sontay supported the implementation of a demand-driven ventilation strategy across the university's seven lecture theatres.

A total of 28 wireless CO₂ and PIR sensors were installed to provide real-time information on both indoor air quality and occupancy.

The wireless devices communicate with the university's existing BMS through the Sontay Bridge, allowing live sensor data to be incorporated directly into the building's control strategy without the need for extensive additional cabling.

Using CO₂ monitoring and PIR motion detection together provides a more accurate picture of how each space is being used.

When either an increase in CO₂ or movement indicates that a lecture theatre is occupied, the associated AHU automatically switches into occupied mode.

During occupied periods:

  • Temperature is controlled to a 22°C setpoint

  • Ventilation responds to maintain CO₂ at approximately 600 ppm

  • Occupied mode remains active for two hours following detection

The two-hour period prevents ventilation from being reduced prematurely during periods where movement may be limited, such as lectures, examinations or presentations.

If no occupancy is detected throughout this period, the system automatically returns to unoccupied mode.

During unoccupied periods, fan speed is reduced to a 20% minimum, maintaining background ventilation while significantly reducing energy consumption. The temperature is also allowed to operate within a wider 18°C–24°C deadband, reducing unnecessary heating and cooling demand.

This creates a fully automated ventilation strategy that responds to how the university's spaces are actually being used rather than relying on fixed operating schedules.

The results

The demand-driven approach has already delivered significant measurable improvements.

Most notably, measured fan power has been reduced by 97.6%, demonstrating the scale of energy that can be saved by moving away from fixed ventilation schedules.

The system also provides continuous insight into CO₂ levels and occupancy, enabling ventilation to respond automatically while maintaining comfortable conditions for students and staff.

Key results

97.6%
Measured reduction in fan power

600 ppm
CO₂ control during occupied periods

22°C
Occupied temperature setpoint

20%
Minimum fan speed during unoccupied periods

7 lecture theatres
Operating with demand-driven control

By combining wireless sensing with the existing BMS, the university has been able to reduce unnecessary ventilation, heating and cooling demand while maintaining indoor air quality and occupant comfort.

The project demonstrates how demand-driven control can provide universities and other education facilities with a practical route towards lower building energy consumption without requiring major changes to existing infrastructure.

Customer feedback

“The system is operating reliably and is effectively supporting operational requirements. It has also delivered clear efficiency improvements, enabling better monitoring and faster response times. Importantly, it is contributing to a strong positive financial impact, aligning with the improved savings and ROI demonstrated post-installation.”

Hard Service Manager, Healthcare, Local Government & Education at MITIE