Components of a controlled mechanical ventilation system

What is the advantage of installing a double flow ventilation system?

A CMV (centralized mechanical ventilation) is a system used to renew the air inside a building or a house. During a renovation project or for a new construction, the question of installing a double flow CMV may arise.

This type of environmentally friendly ventilation would have several benefits for both your health and your energy consumption. But do you know how this air cleaning system works?

What is a double flow ventilation system?

The double flow CMV has the same objectives as a Single flow ventilationIt also offers some improvements. To work, it needs :

  • of a heat exchanger ;
  • a box that integrates a motor that will be in charge of sucking the air from the humid rooms to redistribute it in the rest of the house;
  • insulated ducts (i.e. insulated to prevent heat loss);
  • an outlet (on the roof) to expel the air;
  • an air inlet (also located on the roof to bring in air from outside).
Diagram of a controlled mechanical ventilation system with double flow in a house

The idea is this: rather than losing the heat contained in the air extracted from damp rooms, why not take advantage of it to recover it before expelling the air outside the house? The heat exchanger recovers the heat contained in this stale air and uses it to warm the air drawn into your home. Thus, the cold air from outside is not blown directly into the house, but is preheated before being redistributed to all the non-humid rooms such as the living room or the bedroom.

The system is therefore more complex than a single-flow ventilation system, but offers many advantages. It is undoubtedly a great way to optimise an ecological house or a stand-alone house to reduce the energy consumption of heating.

How to install a double flow CMV?

As you will have understood, the installation of a double flow CMV is not trivial. Indeed, it requires a network of ducts to extract the air and to blow it into each room of your home. You will therefore have to run all these ducts through the false ceilings and insulate them to avoid condensation problems.

In addition, these ducts will need to be connected to motors to eventually be connected to the exchanger, which is usually installed in the attic. The exchanger is usually installed in the attic. It is located close to the roof for the fresh air inlet and the used air outlet, so you will not be bothered by its imposing size.

In order to guarantee good air circulation, it is therefore advisable to call in a professional, as the installation of a double flow ventilation system is quite technical and should not be taken lightly.

Leroy Merlin | How to install a double flow CMV?

The advantages of double flow CMV

There are many advantages to the double flow ventilation system. Among them, we note :

  • reducing heat loss in the house;
  • energy savings (all of which directly implies a more ecological house);
  • a reduction in the discomfort that can be felt in winter with cold draughts;
  • the reversible aspect of the system: the double flow ventilation can be used to heat the air in winter, but also to cool it in summer;
  • the presence of a fresh air filter on the exchanger. The air that enters the house is therefore healthier, filtered of dust, pollen or various particles. This is important for people with allergies or respiratory problems;
  • better insulation against external noise, as the air intake is on the roof.

The disadvantages of a double flow ventilation system

A double-flow ventilation system does not only have advantages. Indeed :

  • Double flow ventilation consumes electricity to operate and is not always cost effective;
  • it requires monitoring and maintenance to maintain its effectiveness;
  • space is needed to store the components that make it work;
  • Good insulation is essential to avoid condensation problems;
  • installation can be costly.
Craftsman replacing a ventilation system hose

So, what is the choice: single flow or dual flow?

Based on this observation, the choice of a double flow ventilation system is not always a good idea. In the case of a new construction, even if it increases the budget somewhat, its choice is strongly recommended.

Indeed, even if the expected energy savings are small, the fact of enjoying healthier air in your home is a strong argument. If you have health problems related to indoor air quality and you want to feel a certain comfort, the double flow ventilation is a good idea. The space required for its installation is easy to foresee when drawing up the plans, so it would be a pity to do without it.

On the other hand, in the context of a renovation project, depending on the space you have available, you may regret opting for the installation of a double flow ventilation system. This could add considerably to the cost. If you have the budget and the space to install it, don't hesitate. However, you should know that for the installation of a double-flow VMC, you should count on a budget of between €2,000 and €5,000. The upper range is for renovation and the lower range is for a new project.