Since 2020, "ventilation" has transformed from an obscure HVAC term into a core element of public health. Offices, schools, hospitals, hotels—all densely occupied spaces have been mandated to "enhance ventilation." However, building operators face a tricky dilemma:
Traditional fresh air systems typically use a "constant volume" design—regardless of actual occupancy, air is supplied based on maximum design capacity. This粗放 management approach results in buildings being "over-ventilated" during most operating hours, wasting enormous amounts of energy.
The solution lies in Demand-Controlled Ventilation (DCV)—dynamically adjusting fresh air volume based on actual occupancy density and air quality, finding the optimal balance between health and energy efficiency.
CO₂ concentration is the best indicator of indoor air quality and occupancy density. When more people enter a room, exhaled CO₂ raises the concentration; when ventilation improves or occupancy decreases, CO₂ levels drop. By monitoring CO₂ in real-time, the fresh air system knows precisely "how much air is needed."
Project data shows that DCV systems with CO₂ linkage control can save 20%-50% of fresh air energy consumption. The greater the occupancy fluctuation (e.g., conference rooms, lecture halls, classrooms), the larger the energy-saving potential.
Even with demand-controlled supply, the temperature difference between fresh air and exhaust air represents significant energy loss. In summer, 25°C indoor air is exhausted while 35°C outdoor air is introduced; in winter, the opposite occurs. Heat recovery technology exchanges energy between supply and exhaust air through heat exchangers, dramatically reducing fresh air conditioning energy.
| Type | Efficiency | Applicable Scenarios | Notes |
|---|---|---|---|
| Rotary Enthalpy Recovery | 70%-85% | Large commercial buildings, hospitals | Minimal cross-contamination risk; not suitable for toxic exhaust |
| Plate Sensible Heat Recovery | 50%-70% | Offices, schools | No cross-contamination; recovers temperature but not humidity |
| Heat Pipe Recovery | 45%-65% | Retrofit projects with space constraints | No moving parts, simple maintenance, moderate efficiency |
In severe cold regions, heat recovery units also need frost protection—when exhaust temperature drops below freezing, bypass or preheating is activated to prevent frost blockage of the heat exchanger.
Within a single building, different functional zones have vastly different fresh air requirements. Conference rooms may be empty in the morning, then suddenly fill with 30 people in the afternoon; offices are occupied during the day but empty at night; corridors and restrooms require continuous ventilation.
Fresh air systems do not operate in isolation. In intelligent building management systems, they need to collaborate with multiple subsystems:
Precise control relies on high-quality sensing layers. Key sensor deployment points for intelligent fresh air system control:
Intelligent fresh air systems are not simply "adding a sensor and installing a VFD." They require establishing a complete closed loop of "sense-analyze-decide-execute" from the design stage. CO₂ concentration linkage control addresses "how much air to supply," heat recovery addresses "don't waste energy," zoned regulation addresses "where air is needed," and BMS integration addresses "how to coordinate with other systems."
As healthy buildings become the mainstream trend, a well-designed, properly commissioned, and operationally standardized intelligent fresh air control system serves both as a defense line for occupant health and a gold mine for挖掘 building energy-saving potential. For building automation system integrators and energy managers, this is one of the most worthwhile technology upgrade directions to invest in today.
Zhiyinghui focuses on sensor and IoT technology, providing complete hardware solutions from the sensing layer to the data layer for fresh air system intelligentization. For inquiries about CO₂ sensors, air quality monitoring modules, or system integration support, please contact our technical team.
