The quality of air in our homes is critical for our well-being, yet it is often overlooked. Indoor air pollution can cause various health problems, such as allergies, asthma, and respiratory diseases. A controlled mechanical ventilation system is an essential component of modern homes, and the double-flow system is gaining popularity for its ability to provide both comfort and energy efficiency.

What is Controlled Mechanical Ventilation Double Flow?

Controlled Mechanical Ventilation (CMV or VMC double flux in french) Double Flow is a system designed to ventilate buildings while minimizing heat loss or gain. It provides fresh air to living spaces while extracting stale air from the building. The system uses two ducts, one for supply and one for exhaust. The supply duct brings fresh air from outside, which is then filtered and distributed to the living spaces. The exhaust duct extracts stale air from the building and expels it outside.

The double-flow system is particularly beneficial in cold climates, where heat loss can be a significant issue. The system includes a heat exchanger that transfers heat from the stale air to the incoming fresh air, which reduces energy consumption and keeps the home warm.

How Does the Double Flow System Work?

To better understand the double-flow system, let us take an example of a typical residential building. The system comprises several components, including a heat exchanger, a fan, and two ducts.

Firstly, the fan draws fresh air from outside into the heat exchanger, which filters it and preheats it using the heat from the stale air being extracted. The preheated air then passes through the supply duct, which distributes it to the various living spaces in the building.

Secondly, the fan draws stale air from the living spaces into the heat exchanger, where it passes through the opposite side of the heat exchanger, transferring its heat to the incoming fresh air. The stale air is then expelled through the exhaust duct to the outside.

The system is designed to maintain a constant flow of fresh air into the building while exhausting stale air. The heat exchanger ensures that the fresh air is preheated in winter, and in summer, it can be used to cool the incoming air. The system also includes filters to remove airborne pollutants, such as dust, pollen, and bacteria.

Benefits of Controlled Mechanical Ventilation Double Flow

  1. Improved Indoor Air Quality

The primary benefit of the double-flow system is that it provides fresh air to living spaces, which improves indoor air quality. The system filters the incoming air, removing airborne pollutants, which can cause respiratory problems and allergies. The system also exhausts stale air, removing excess moisture and carbon dioxide, which can cause health problems.

  1. Energy Efficiency

The double-flow system is an energy-efficient way of ventilating buildings. The heat exchanger transfers heat from the stale air to the incoming fresh air, reducing energy consumption. In winter, the system preheats the incoming air, which reduces the load on the heating system, thus saving energy. In summer, the system can be used to cool the incoming air, reducing the load on the air conditioning system.

  1. Comfort

The double-flow system provides a constant supply of fresh air, which improves indoor air quality and creates a comfortable living environment. The system also removes excess moisture, which can cause condensation and mold growth. The constant flow of air helps to maintain a consistent temperature and humidity level, providing a comfortable living environment.

  1. Noise Reduction

The double-flow system is designed to operate quietly, minimizing noise pollution. The system uses low-noise fans and is often installed in areas of the building, such as the basement or attic, where noise levels are less of a concern.

  1. Long-term Cost Savings

While the initial cost of installing a double-flow system may be higher than a traditional ventilation system, the long-term cost savings are significant. By providing better air quality while using less energy, double-flow systems can result in lower energy bills and reduced maintenance costs over time.

The use of heat recovery technology in double-flow systems also contributes to long-term cost savings. By capturing and reusing heat that would otherwise be lost, the system reduces the amount of energy needed to heat or cool the building. This not only lowers energy bills, but also reduces the wear and tear on heating and cooling equipment, leading to lower maintenance costs.

Furthermore, improved air quality can lead to health benefits for building occupants, which can translate into long-term cost savings as well. Studies have shown that poor indoor air quality can lead to a variety of health problems, including respiratory issues, headaches, and fatigue. By providing clean, fresh air, double-flow systems can help reduce the incidence of these health issues, leading to lower healthcare costs and improved productivity among building occupants.

Example of Long-Term Cost Savings: A School in France

A school in France provides an example of the long-term cost savings that can be achieved through the use of a double-flow ventilation system. The school, which was built in 2013, features a ventilation system that includes a heat recovery unit and CO2 sensors to regulate air flow.

The system has led to significant energy savings for the school. According to a case study by the French Ministry of Ecology, Energy, and Sustainable Development, the school has achieved energy savings of 57% compared to a traditional ventilation system. This translates to an annual energy cost savings of €13,300 (approximately $15,600).

In addition to the energy savings, the ventilation system has also led to improved air quality in the school. CO2 levels are kept within recommended levels, and the system provides fresh, filtered air throughout the building. This has led to improved health and productivity among students and teachers, as well as reduced absenteeism.

The long-term cost savings achieved by the school demonstrate the potential benefits of double-flow ventilation systems. While the initial cost may be higher, the energy savings and improved air quality can result in significant cost savings over time.


Controlled mechanical ventilation double flow systems provide numerous benefits for building occupants, including improved air quality, energy efficiency, and long-term cost savings. By using heat recovery technology and regulating air flow, these systems provide clean, fresh air while minimizing energy use.

While the initial cost of installing a double-flow system may be higher than a traditional ventilation system, the long-term benefits can make it a worthwhile investment. By reducing energy bills and maintenance costs, as well as improving health and productivity among building occupants, double-flow systems offer a cost-effective solution for providing high-quality ventilation in buildings of all types.