Ventilation System A: Natural Ventilation Clearly Explained

In ventilation system A, both the supply of fresh air and the exhaust of stale air occur naturally. That means: no fans, no complex duct systems, and no electricity consumption. Fresh air enters through grilles located in windows, doors or exterior walls. These grilles are usually equipped with a regulator to adjust the air supply.

The exhaust takes place through vertical ducts that terminate on the roof. Warm, stale air rises naturally and leaves the home via these ducts. This is called the chimney effect. Wind around the roof also creates additional draft, enhancing the exhaust. The entire system is therefore completely dependent on natural forces.

The advantages of ventilation system A at a glance

Ventilation system A offers several clear advantages, especially for homes where simplicity and ease of maintenance are key:

• Extremely low energy consumption: because no fans are running, the system uses no electricity. This saves on the energy bill and makes it a sustainable choice.
• Minimal maintenance: without mechanical parts, there is hardly any wear. Cleaning the grilles occasionally and checking the ducts is sufficient.
• Quiet: there is no motor noise, only the soft rustle of wind through the grilles.
• Simple installation: installation is relatively easy, especially during renovation, as you don't need complex ducts or power supply.
• Continuous basic ventilation: the system works 24/7, even during power outages.

Disadvantages and limitations

Besides the advantages, ventilation system A also has clear disadvantages. Especially in modern, well-insulated homes, the performance can be disappointing:

• Dependent on the weather: during calm or warm weather, ventilation can be greatly reduced. In summer, stale air does not always rise on its own, which can worsen indoor air quality.
• No heat recovery: unlike ventilation system D, all heat from the exhaust air is lost. This leads to higher heating costs.
• Limited adjustability: you cannot finely tune the ventilation to occupancy or moisture production. Cooking, showering or having many visitors requires extra ventilation by opening windows.
• Less suitable for airtight homes: in highly insulated and draft-proof new buildings, the natural supply may be insufficient, leading to moisture problems.

Ventilation system A in Flemish homes

In Flanders, ventilation system A is still common in older terraced houses, apartments and farmhouses. These homes are often not extremely airtight, so the natural supply through gaps and grilles runs smoothly. During energy renovations, the system is often replaced by a more controlled ventilation system C or D, but for those who consciously choose simplicity and minimal interventions, A remains a valid alternative.

Note: since the EPB regulations, minimum ventilation rates apply. An existing natural system must meet these requirements; otherwise, it may be necessary to install additional grilles or switch to mechanical assistance.

Costs and installation of ventilation system A

The total price of a ventilation system A depends on the type of grilles, the number of ducts and the complexity of the installation. On average, you can expect €1,500 to €3,000 for a complete installation in an average home, including placement. That is significantly lower than with ventilation system D (often €5,000 to €8,000).

Especially for renovations, system A can be attractive for budget reasons, as no demolition work is needed for duct systems. Would you like an exact tailored price? Request your quote now and receive no-obligation advice from our specialists in your region.

Ventilation system A versus other systems

The choice between ventilation systems A, B, C and D is not always easy. While system A operates entirely naturally, ventilation system C uses mechanical exhaust (usually in the kitchen, bathroom and toilet) and natural supply. Ventilation system D (balanced ventilation) supplies and exhausts everything mechanically, with heat recovery. System B (reverse: mechanical supply, natural exhaust) is rare. Each system has its own price tag, comfort level and energy consumption. The best choice depends on your type of home, budget and comfort preferences.

Maintenance and tips

Maintenance of a ventilation system A is minimal. Nevertheless, regular inspection is important to prevent mold or blockages. Clean the grilles every two months with a damp cloth and check annually that the exhaust ducts are clear. Have the ducts professionally swept every three to five years, just like a chimney.

Best time to install: April as the ideal lead-up to May

Demand for ventilation systems traditionally peaks in May, when many people prepare their homes for summer. Those who take action now in April enjoy shorter waiting times and can benefit from a healthy indoor climate in time for the warm days. Our installers still have availability to schedule quickly in this period. Don't hesitate and request your quote now to be ready before the May rush.