The role and installation of ventilation in a house

When we talk about the comfort and health of a home, ventilation often plays a central role. Indeed, properly ventilating your home is not only a question of olfactory comfort: it is also a health issue, preserving the building and improving quality of life. The importance of ventilation is sometimes underestimated, even though it plays a fundamental role in removing humidity and pollutants from the air, as well as in bringing in fresh air. For those who are considering installing or renovating a ventilation system in their home, this article provides an overview of the main issues, existing systems and good practices to adopt. www.lheat.be

Why is ventilation essential?

Ventilation is not just about eliminating bad odours: its role goes far beyond that. In a home, indoor air can be up to five times more polluted than outdoor air due to the accumulation of different substances. Furniture, cleaning products, heating appliances or even the presence of mould and mites can release harmful or irritating particles. Without an air renewal system, these pollutants accumulate and can cause respiratory problems, irritations or allergies.

Good ventilation also helps prevent excess humidity. Excessive humidity, or a water damage is often the cause of mold, fungus and various types of damage (peeling paint, crumbling plaster, etc.). In addition to the aesthetic inconveniences, the health consequences are real: increased risks of asthma, allergies and other respiratory conditions. The evacuation of humidity, whether from cooking steam, the bathroom or the laundry room, is therefore crucial to maintaining a healthy indoor environment.

Finally, ventilation contributes to thermal comfort. In summer, the movement of fresh air from natural or mechanical ventilation can slightly cool the home, while in winter, a good ventilation system coupled with efficient insulation can help maintain a pleasant indoor climate. It is therefore essential to think about ventilation when designing a house or during renovation work in order to ensure an optimal balance between comfort, health and energy performance.

The different types of ventilation systems

The choice of a ventilation system depends on many criteria: budget, construction method (renovation or new), technical constraints, desired energy performance, etc. In general, there are two main categories: natural ventilation and controlled mechanical ventilation (CMV). The latter can itself be available in several versions. Understanding the characteristics of these different systems allows you to choose the solution best suited to your project.

Natural ventilation

Natural ventilation is based on the principle of aeration by air currents, facilitated by permanent or occasional openings (e.g.: air vents, open windows). The air is renewed autonomously, without the aid of a mechanical device, thanks to the differences in temperature and pressure between the inside and the outside.

This solution may seem simple and economical. However, it has two major limitations: on the one hand, it is highly dependent on climatic conditions (in the absence of wind or with outside temperatures close to those inside, air renewal may be insufficient). On the other hand, natural ventilation is not controlled, which can lead to heat loss in winter and a lack of fresh air in summer. However, in some old houses or in specific configurations, it can represent an acceptable compromise.

Single flow controlled mechanical ventilation (CMV)

Single-flow CMV is probably the most widespread solution in homes. Its operation is relatively simple: an extractor generally located in the attic or in a technical room sucks in stale air through extraction vents placed in damp rooms (kitchen, bathroom, toilets). Fresh air enters the home through air inlets, often located at the top of windows or walls, mainly in living rooms (living room, bedrooms).

One of the main advantages of single-flow CMV is its value for money. Installation is less expensive than some more complex systems, and maintenance remains fairly simple (regular cleaning of the extraction vents and air inlets). However, in winter, the heat from the indoor air is directly rejected outside, which can cause heat losses and therefore increase heating costs.

Double flow controlled mechanical ventilation (CMV)

Unlike single-flow CMV, double-flow CMV ensures both the extraction of stale air and the insufflation of fresh air, thanks to two separate circuits. The key device that distinguishes double-flow CMV is the heat exchanger: it can recover up to 90% of the heat contained in the outgoing air to preheat the incoming air. Thus, in winter, heat losses are considerably limited, and heating savings can be substantial.

The dual-flow CMV has other advantages, including the ability to filter the fresh air to retain dust, pollen and other allergenic particles. This system therefore provides healthier air and reduces the risk of allergies. However, its installation is more complex and expensive: a larger network of ducts and space for the heat exchanger must be provided. In addition, to optimize energy performance, it is essential that the house is well insulated and airtight, otherwise a large part of the expected benefits will be lost.

Other ventilation systems

Beyond the single-flow and double-flow CMV, there are other devices such as the VMR (Distributed Mechanical Ventilation) or the hygroregulated CMV. The VMR is suitable for renovations, because it allows several small independent extractors to be installed in each of the wet rooms. As for the hygroregulated CMV, it automatically adjusts the air flow according to the ambient humidity level, which allows better control of energy consumption. The choice is made according to the configuration of the house, the local climate, the available budget and the sensitivity of the occupants to air quality.

How to successfully install a ventilation system?

Installing a ventilation system, especially a dual-flow CMV, is a project that should not be taken lightly. To obtain an optimal result, it is strongly recommended to call on qualified professionals. However, here are some key points to consider:

1. Establish a preliminary diagnosis

In order to determine the real ventilation needs, a diagnosis of the habitat is essential. The professional will study the configuration of the rooms, the surface area, the level of insulation and airtightness, as well as the possible presence of humidity or mold phenomena. At the end of this step, he will be able to propose the most suitable system (single flow, double flow, VMR, etc.) and correctly size the installation.

2. Choose a wise location for the equipment

The VMC and its motor must be placed in an accessible room, often in the attic or a false ceiling, in order to facilitate maintenance and servicing. For the double flow VMC, the heat exchanger occupies a certain amount of space and requires easy access for regular replacement of the filters. In addition, it is recommended to ensure the soundproofing of the room to avoid possible noise pollution.

3. Take care of the sealing and insulation of the ducts

In the case of a dual-flow CMV, air circulation is done via a network of supply and extraction ducts. To avoid air leaks and maintain energy performance, it is advisable to choose quality ducts that are well insulated and correctly connected. The passage points (walls, ceilings) must be carefully sealed. The ducts must also be installed in such a way as to minimize bends and unnecessary lengths, in order to limit pressure losses and aerodynamic noise.

4. Carry out commissioning and final adjustments

Once the installation is complete, it is important to carry out operational tests and check the flow of extracted and supplied air in each room. The settings must be carried out precisely in order to guarantee sufficient air renewal, while avoiding excess energy consumption or pressure imbalances that could lead to unpleasant draughts.

5. Ensure regular maintenance

Regardless of the ventilation system chosen, regular maintenance is essential to maintain all its performance. This mainly involves:

• Clean or replace the filters in the case of a double flow CMV.
• Check the condition and cleanliness of the extraction and insufflation vents.
• Regularly maintain the air inlets (in the context of a single-flow CMV).
• Call a professional to check the ductwork and the general performance of the system every two or three years, especially if the VMC shows signs of malfunction.

Maintenance is often neglected, even though it directly affects the quality of indoor air and the durability of the installation. A poorly maintained ventilation system can lose a large part of its efficiency and even become noisy or energy-intensive.

Ventilation and energy efficiency: an inseparable duo

In a context where the energy performance of housing is increasingly regulated by regulations (RT 2012, RE 2020 in France, for example), ventilation is becoming a determining factor. New houses, often well insulated and airtight, absolutely need a controlled ventilation system to avoid the stagnation of stale air. Heat loss linked to ventilation can represent a significant part of the heating bill. This is why the double flow CMV, by recovering the heat from the outgoing air, is a solution of choice to reconcile air quality and control of energy costs.

Furthermore, according to theADEME, a poorly ventilated house promotes condensation and increased humidity levels, which can have a significant impact on the energy performance of the entire building. Occupants, to eliminate this feeling of humidity, will tend to overheat their home, thus generating additional energy costs and a higher carbon footprint. Hence the interest in thinking about installing or renovating a quality ventilation system to make savings in the long term.

The Importance of Overall Home Design

A good ventilation system is not everything: it must be integrated into an overall design of the house that includes insulation, airtightness, room distribution and the location of openings (windows, French windows, etc.). In new builds, architects and thermal design offices work hand in hand to optimize these parameters, ensure good distribution of air flows and minimize thermal bridges.

In renovation, the situation can be more complex. The constraints linked to the existing (load-bearing walls, layout of the premises, etc.) can limit the possibilities of installing certain devices. It is therefore advisable to carry out a complete energy audit to determine the best possible solutions, both in terms of insulation and ventilation. The work can be an opportunity to rethink the interior layout, to create or move certain openings, or to insulate the attic and walls before installing a more efficient CMV.

Finally, the overall design must take into account the future use of the house. A family home with several children generates more humidity and pollutants (cooking, frequent showers, etc.) than a house occupied by a single person. Similarly, the presence of pets, plants or additional heating devices (wood stove, fireplace) can influence the quantity of suspended particles and, consequently, the ventilation requirements.

What budget should I plan for installing a ventilation system?

The budget for installing a ventilation system varies depending on the type of device chosen, the surface area of ​​the home, the condition of the existing building and the complexity of the installation (presence or absence of attic, accessibility constraints, etc.). Here are some major trends:

• Natural ventilation : It can be very inexpensive if you limit yourself to installing air vents and regular manual ventilation. However, the lack of air control can result in higher heating costs.
• Single flow CMV : This is the most affordable system. For new builds, the installation budget is generally between 1 and 000 euros, including supplies and installation. For renovations, additional work is sometimes required (core drilling of walls, false ceilings) which increases the cost.
• VMC dual streams : More expensive, it can cost between 3 and 000 euros, or even more, depending on the surface area, the brand of equipment and the complexity of the duct network. However, the heating savings achieved in the long term and the significant improvement in indoor air quality often justify this investment.
• Specific solutions (VMR, hygroregulated VMC, etc.) : Costs vary greatly depending on the options chosen (type of regulation, accessories, filters, etc.). It is therefore advisable to request several quotes from professionals to compare services and assess the quality-price ratio.

Let's not forget that many financial aids (tax credits, energy renovation bonuses, etc.) can encourage the installation of more efficient systems, in particular dual-flow CMV, as long as the project is part of an overall energy improvement approach for the home.

Conclusion: investing in ventilation for a healthy and efficient home

Ventilation plays a key role in the quality of life of occupants and the sustainability of the building. Beyond its immediate impact on health and comfort, it also influences the energy performance of the house, by helping to avoid excess humidity and regulate air circulation. To choose the most suitable solution, many criteria should be taken into account: the condition of the existing building, the level of insulation, budgetary constraints and the occupants' expectations in terms of comfort and health.

Whether you opt for a single-flow, double-flow, natural VMC or a more specific solution such as VMR, the important thing is to take the time to properly assess your needs, seek expert advice and never neglect maintenance. Once the right system is in place, you will quickly see the benefits on indoor air quality and your energy bills, while protecting your home from moisture-related damage.