Airflow control and indoor air quality solutions
In modern tertiary buildings (offices, schools, public-access buildings), ventilation plays a central role in indoor air quality (IAQ) and the energy performance of HVAC systems.
Variable Air Volume (VAV) control systems make it possible to adjust airflow to occupants’ needs. This approach enables simultaneous optimization of:
Airflow control is now a key lever for HVAC design offices, operators, and project owners looking to deliver high-performance buildings that comply with the latest regulatory requirements.
F2A provides a complete range of air control solutions designed to cover all types of tertiary building configurations: new build, renovation, and occupied buildings.
The offering is based on three complementary pillars: airflow control (VAV, CAV), ductwork stability (pressure), and intelligent indoor air quality control via a dedicated platform.
The main objective is to address comfort, health, energy performance, and ease of implementation challenges, both in new construction and renovation projects.
Technical and energy strategy
Variable airflow ventilation systems allow ventilation to be adjusted room by room according to the building’s actual needs.
Unlike constant airflow systems, VAV systems enable:
- optimization of air renewal
- reduction of fan energy consumption
- improved thermal management of spaces
In commercial buildings, energy savings can reach 30 to 40% compared to constant airflow ventilation systems.
Outdoor air treatment represents a significant share of the energy consumption in a commercial building.
Each cubic meter of outdoor air introduced into the building must be:
- heated in winter
- cooled in summer
- filtered
- sometimes dehumidified
Ventilation in commercial buildings is still mainly based on the use of air handling units operating at constant pressure (or with airflow variation). Energy savings mainly depend on the consumption of the air handling unit.
This unit is controlled by a constant pressure control loop. It reacts and adjusts its speed according to variations in airflow and pressure within the ductwork.
New ventilation concepts
Free cooling in commercial buildings consists of using outdoor air to provide cooling when its temperature is lower than that of indoor air. The principle is based on the operation of the air handling unit and VAV/eVAV terminals.
In practice, when conditions are favorable (typically at night), the air handling unit opens its outdoor air dampers up to 100% outdoor airflow and bypasses the cooling coil. At the same time, VAV systems no longer modulate airflow based on occupancy but operate at maximum airflow across all zones to maximize fresh air intake and ensure overall building cooling.
The main benefit is “free” cooling through maximum ventilation of spaces, reducing the need for mechanical cooling. This operating mode is particularly suitable for offices, schools, or high-occupancy buildings, especially during mid-season or in temperate climates.
In the context of leasing office spaces to different tenants, airflow requirements vary significantly depending on occupancy and layout (open space, meeting rooms, partitioning).
Two technical approaches ensure proper implementation of this type of project:
- constant pressure control at each branch inlet per floor
- integration with a BMS (Building Management System)
The benefit of a VAV system combined with constant pressure controllers per floor is to maintain dynamic airflow balance adapted to each floor. Each floor can define its operating pressure during final commissioning to ensure both acoustic and aeraulic comfort. Pressure control is therefore decentralized from the air handling unit to the floor level. Each floor becomes independent and can be adjusted for its
own operation.
The advantage of a VAV system controlled via the BMS is the ability to remotely reconfigure airflow without on-site physical intervention: each zone can be adjusted in airflow setpoint, operating range, or control logic (CO₂, temperature) directly through the system.
At terminal level, unlike conventional dampers that impose a fixed mechanical setting, VAV dampers offer high flexibility during tenant changes or space reconfigurations. They eliminate the need for manual rebalancing of the ductwork and repeated on-site interventions.
The use of VAV dampers also enables accurate monitoring of actual airflow and dynamic control. They ensure comfort and energy performance while simplifying multi-tenant operation with independent and scalable zoning.
In variable airflow HVAC systems, traditional fan control based on constant pressure quickly reaches its limits in terms of energy efficiency. When demand decreases, pressure remains artificially high in the ductwork. VAV dampers then compensate by closing significantly to maintain their airflow setpoints.
This operation generates unnecessary pressure losses and increased fan energy consumption. Several studies show that dynamic control based on the actual position of VAV dampers allows pressure to be adjusted to real demand. The principle is to use damper position feedback as an indicator of ductwork load. The air handling unit then adjusts fan speed to keep VAV dampers within an optimal operating range.
This approach repositions dampers in an intermediate operating zone that is more stable and efficient. The ductwork then operates at the minimum required pressure, without overpressure.
The energy benefit is immediate: fan power decreases significantly with pressure. In commercial buildings, energy savings typically range from 20% to 50%, with some cases showing reductions of up to 60% to 65%.
Beyond reducing energy consumption, this control strategy also improves acoustic comfort and airflow stability. It reduces mechanical stress on VAV actuators. Damper position thus becomes a key indicator of the system’s energy performance. An optimized ductwork system is one where VAV dampers are neither too closed nor fully open.
Source: https://www.rehva.eu/rehva-journal/chapter/vav-system-with-genuinely-demand-controlled-fans
Airflow diversity in commercial buildings, particularly in office spaces, is not a regulatory requirement.
It is primarily a design method used by engineering consultants to avoid sizing ventilation systems based on the assumption that all zones operate simultaneously at maximum airflow. This approach, based on variations in occupancy and indoor air quality, avoids systematically oversizing for peak loads.
Airflow diversity helps optimize system sizing and reduce air handling unit capacity. The AHU becomes more compact and cost-effective, providing direct project savings. It also allows ventilation to better match actual building usage. With sensors, VAV dampers, and a control system, energy is used more efficiently, resulting in operational savings.
However, airflow diversity must be applied with caution. If poorly implemented, it can quickly lead to underperforming ventilation systems. An overly optimistic diversity factor may result in insufficient airflow during real high-occupancy conditions (meetings, densification, return to office), leading to degraded indoor air quality and comfort.
This can cause design issues that are difficult to correct during operation. If actual occupancy patterns differ from initial assumptions, an undersized ventilation system may not be recoverable without replacing the air handling unit.
In constantly evolving commercial buildings, a fixed diversity assumption quickly becomes obsolete. Without flexibility or capacity margin, the system may become unsuitable or even non-compliant with indoor air quality and energy performance requirements.
The main pitfall is to consider airflow diversity as an alternative to control. Without precise control (VAV, sensors, BMS), the risks of airflow imbalance, overpressure, or under-ventilation are significant. It is therefore essential to adapt system design by implementing connected and intelligent solutions.
Regulatory context
Indoor air quality (IAQ) is a major public health issue, especially in commercial buildings where people spend up to 85% of their time. Poor indoor air quality can impact both health and productivity. In France, poor IAQ is estimated to cost around €19 billion per year.
Ensuring adequate outdoor air renewal is essential for occupant health and comfort. Ventilation systems must be designed with variable capacity to match actual demand. (Sources: WHO & OQAI 2024).
In France, regulations require indoor air quality (IAQ) monitoring in certain public-access buildings, such as daycare centers and educational facilities.
| Criteria | Room types | Regulatory requirements | Local regulation |
|---|---|---|---|
| Offices | Individual and open-plan offices, break rooms, lobbies | 25 m³/h per person | 18 m³/h per person |
| Meeting rooms | Meeting rooms, dining areas | 30 m³/h per person | 22 m³/h per person |
| Educational facilities | Classrooms, libraries, multi-purpose rooms | 25 to 30 m³/h per person | 18 m³/h per person |
The French Sanitary Regulations (RSDT) and the Labor Code define minimum outdoor airflow requirements depending on zone type and building typology.
The EN 16798-3 standard defines indoor air quality requirements for non-residential buildings. Based on a reference outdoor CO₂ concentration of 400 ppm, indoor air is classified into four categories according to CO₂ levels.
| ID1 | High indoor air quality | below 800 ppm |
| ID2 | Good quality | 800 to 1000 ppm |
| ID3 | Moderate quality | 1000 to 1400 ppm |
| ID4 | Low quality | above 1400 ppm |
BACS regulation (Building Automation and Control Systems)
The French Sanitary Regulations (RSDT) and the Labor Code define minimum outdoor airflow requirements depending on zone type and building typology.
The EN 16798-3 standard defines indoor air quality requirements for non-residential buildings. Based on a reference outdoor CO₂ concentration of 400 ppm, indoor air is classified into four categories according to CO₂ levels.
The objective is to continuously monitor, control, and optimize technical systems, including ventilation.
Source: https://www.legifrance.gouv.fr/jorf/id/JORFTEXT000047422489
Historically, ventilation systems were designed based on fixed assumptions (constant airflow, peak load scenarios). The BACS regulation introduces a shift in approach:
- monitoring of actual performance
- adaptation to operating conditions
- detection of deviations
- continuous optimization
Ventilation becomes a dynamic system that must be controlled according to actual occupancy. Measuring CO₂ as an indicator of air confinement enables real-time adjustment of airflow. Control strategies can become more advanced to reduce energy consumption and ensure performance during operation.
Deadlines:
| April 8, 2024 | January 1, 2025 | January 1, 2030 |
|---|---|---|
| New buildings equipped with systems over 70 kW | Existing buildings equipped with systems over 290 kW | Existing buildings equipped with systems over 70 kW |
How to answer it:
To comply with the BACS regulation, systems must meet four key requirements related to monitoring, analysis, interoperability, and system management:
- continuous monitoring of energy performance
- analysis of system operation and detection of deviations
- interoperability between building systems
- centralized and efficient control of technical systems
In addition, periodic inspection of these systems is mandatory to ensure proper operation and ongoing performance.
Sources: Article R175-3 of the French Construction and Housing Code and Hellio infographic on the BACS regulation.
Different
markets
VAV dampers are pressure-independent systems that enable precise control of ventilation airflow. Airflow measurement is integrated into the damper (cross-flow measurement principle) to monitor and control airflow regardless of upstream pressure variations in the ductwork. Each space is therefore independent from the others.
With regulations and energy efficiency labels, measuring and monitoring ventilation airflow in buildings has become essential. Thanks to VAV dampers with integrated cross-flow measurement, it is possible to continuously access airflow data room by room. Communicating actuator versions (Modbus, BACnet) are also available to transmit data to the BMS.
Example of variable airflow ductwork design
Design of a VAV damper ductwork system with supply and return in each room → supply and return via VAV dampers in each space → airflow balance of the ductwork ensured at each room level.
A constant pressure control damper is a VAV-type damper system controlled by a pressure controller installed on the ductwork. It regulates the pressure of a building zone for both supply and exhaust airflow.
It is possible to control the pressure of a ductwork branch using an additional pressure controller installed on the damper. In addition, constant pressure control dampers equipped with a cross-flow measurement device provide continuous airflow measurement, which can be transmitted to another damper or to the BMS.
These systems are essential for pressure management in commercial spaces (offices, meeting rooms) and educational facilities. They can be tailored to specific requirements and offer various options (special coatings, insulation, etc.).
Example of a constant pressure control damper installation
Installation of VAV dampers on supply in each room with a common return:
- Supply airflow with VAV dampers in each space
- Centralized return airflow
Airflow balance of the ductwork is ensured at zone level by installing a constant pressure control damper. The damper maintains the correct operating pressure in the branch ductwork via the additional pressure controller. Thanks to the cross-flow measurement device, the constant pressure control damper can control a VAV damper on the return side.
Constant airflow (CAV) dampers maintain a fixed airflow regardless of pressure variations in the ductwork. They are particularly suitable for spaces requiring continuous air renewal, such as restrooms, technical rooms, or areas with specific pollution sources.
Their simple operation ensures high reliability and quick installation. They do not require sensors or complex control, which helps reduce installation and maintenance costs.
However, they do not allow airflow to be adjusted based on occupancy, making them less energy-efficient than VAV systems.
In a controlled commercial building, ventilation, control, and supervision systems must continuously exchange data. Communication protocols form the invisible infrastructure that enables interoperability between equipment (air handling units, VAV dampers, sensors, BMS/BACS).
The main HVAC communication protocols available on the market are listed below:
Advantages: high interoperability, recognized standard, ideal for complex commercial projects
Advantages: flexibility, adaptability, wide product range
A low-power radio protocol suited for sensors and autonomous devices (CO₂ sensors, eVAV, etc.). LoRaWAN enables reliable wireless communication within buildings. Gateways must be installed to collect data, which is then transmitted to the BMS using standard protocols (Modbus, BACnet).
The commissioning of a variable airflow system is essential to ensure proper operation and optimized building performance.
Excessive pressure in a ductwork branch can lead to high noise levels in occupied spaces and occupant discomfort. Operating airflow of VAV dampers may also vary between design and actual use: space usage may have changed (office instead of meeting room or vice versa), or occupancy levels may have evolved (more or fewer occupants).
The main actions during commissioning are:
Comfort parameters may also evolve depending on thermal regulations, energy labels (THQE, LEED, BREEAM, etc.), and certifications such as WELL, which define minimum comfort and indoor air quality levels in buildings.
The final tuning phase of VAV systems is critical to ensure proper ventilation performance in a building.
F2A “Air quality, control and supervision” product range
RCVS (circular) and RRVS (rectangular) dampers are designed to ensure precise airflow control in HVAC ductwork. They allow ventilation to be adjusted according to actual occupancy, particularly in offices, meeting rooms, and educational facilities, while easily integrating into existing BMS architectures.
Features:
- VAV or CAV control
- control via analog signal (0–10 V / 2–10 V)
- communication (Modbus, BACnet)
- integration with CO₂ sensors or occupancy sensors
- simple setup during commissioning
VAV dampers contribute to improved indoor air quality and can reduce ventilation energy consumption by up to 30%. This is a proven solution, compliant with market standards and easy to maintain over the long term.
The RRVS / RRVS-I damper is a variable air volume (VAV) system with a rectangular connection. It is used to control the airflow of a zone.
They are available in custom sizes (W x H) from 100×100 to 1000×1000. For larger sizes, please consult us.
Features:
- integrated energy harvesting and storage
- embedded CO₂, temperature, and humidity sensors
- LoRaWAN communication
- direct airflow control based on indoor air quality or occupancy
- master/slave operation for supply and return
e·VAV installation enables a drastic reduction in installation time (up to ~90%) and eliminates wiring costs.
This is a scalable solution adapted to regulatory requirements for schools and offices. It is particularly well suited for renovation projects where space is limited and electrical wiring is more complex.
The e·VAV is a circular variable airflow damper designed to:
- manage outdoor airflow in commercial spaces and classrooms
- control airflow and monitor indoor air quality through integrated sensors (humidity, temperature, and CO₂)
RCPS pressure control is dedicated to stabilizing ductwork systems. It ensures optimal operating conditions for downstream VAV dampers by maintaining constant pressure despite airflow variations related to occupancy.
Pressure control at branch level is widely used in high-rise buildings. It allows each floor to be stabilized with a pressure setpoint adapted to actual occupancy conditions.
Features:
- real-time pressure measurement
- automatic control loop
- compatibility with existing VAV architectures
- optimization of ductwork balancing
Pressure control helps maintain consistent comfort throughout the building, reduce airflow imbalances, and improve commissioning reliability.
F2A advantage: our pressure controllers integrate a cross-flow measurement device, enabling monitoring and control of other VAV dampers. This is the ideal solution for duplicating airflow control on return ductwork.
Circular VAV damper equipped with a mounted pressure controller and a duct-mounted Pitot tube.
SiMo is a supervision and control platform dedicated to VAV and e·VAV systems. It acts as a “light BMS” specialized in ventilation, providing a clear and actionable view of indoor air quality without the complexity of a traditional BMS.
Below are some of the features available on SiMo:
- real-time monitoring of CO₂, temperature, and humidity
- airflow aggregation
- scheduling management
- intelligent free cooling
- ductwork balancing
- LoRaWAN and Modbus communication
- intuitive web interface with local data storage
SiMo provides immediate access to IAQ data, enables ventilation optimization at building scale, and reduces integration costs. It is a no-recurring-fee solution, ideal for operation and maintenance.
F2A provides commissioning support services for VAV and e·VAV systems. With its network and in-house expertise, benefit from F2A’s efficiency to ensure a smooth startup of your installations.
Support for commissioning, system tuning, and installation of VAV and e·VAV dampers includes:
- installation support
- product configuration
- ventilation system tuning
- commissioning report
Our teams are available Monday to Thursday from 8 a.m. to 5:30 p.m. and Friday from 8 a.m. to 4:30 p.m.