Ventilation System D: Clear Explanation and Local Installation in Flanders

How does ventilation system D work?

The heart of the system is the ventilation unit with heat exchanger, usually installed in the attic, basement or technical room. From this unit, air ducts run to humid rooms (kitchen, bathroom, toilet, utility room) for exhaust of stale air, and to dry rooms (living room, bedrooms, office) for supply of fresh air. Two fans in the unit ensure the airflows. The heat exchanger, a cross-flow or counter-flow exchanger, transfers heat from the exhaust air to the supply air. Then the fresh air is filtered and distributed.

Most systems have a bypass function: in summer, when the outside temperature is higher than inside, the heat exchanger can be bypassed so you can ventilate with cooler outdoor air without heating up the home.

Advantages of ventilation system D

• Energy-efficient ventilation: Up to 90% heat recovery, significantly reducing your heating costs. In a well-insulated home, it can lower your E-level by 20 to 30 points.
• Continuously healthy indoor climate: Constant air renewal without drafts, with fine filtration of pollen and dust. Ideal for allergy sufferers.
• No wall vents: Because supply is mechanical, you don't need trickle vents above windows, which improves insulation and reduces outside noise.
• Quiet operation: With proper sizing and sound attenuation, you barely hear the system in living spaces.

Are there disadvantages to ventilation system D?

• Higher investment: Purchase and installation are higher than system C due to the dual mechanical drive and ductwork. On average, a complete system D for a home costs between €4,000 and €8,000, including installation.
• Maintenance: Filters must be replaced every 3 to 6 months (cost around €25 per set), and every 2 years the ducts need cleaning. Without proper maintenance, efficiency drops and air quality can deteriorate.
• Installation during renovation: In existing homes, placing air ducts can be a challenge, but with smart custom solutions it is almost always possible, especially in Flemish houses with sufficient space.

Difference between ventilation system C and D

System C exhausts mechanically and supplies naturally via window vents. It is simpler and cheaper, but you always feel drafts near the vents and heat is lost. System D offers heat recovery and filters the supplied air. For new construction, system D is the standard; for major renovations it is often the best choice if you aim for a low E-level. Want to understand the differences in detail? Read our comparison between system C and D.

What does ventilation system D cost in 2025?

The price depends on the size of your home, the type of unit (airflow rate, heat exchanger efficiency), the brand (such as Vasco, Renson, Zehnder...), and the complexity of installation. For an average single-family home of 150 m², you pay for a basic system D including installation from about €5,000 to €7,000. For a more luxurious version with higher efficiency, CO₂ control and app control, it can go up to €10,000. Request a no-obligation quote tailored to your project.

Can I install a ventilation system D myself?

We strongly advise against installing a balanced ventilation system yourself. Installation requires specialist knowledge of airflows, duct airtightness, acoustic damping and EPB certification. Mistakes lead to noise, drafts, energy loss or an invalid EPB declaration. Always choose a certified installer, like ours, who has experience in your region.

Maintenance of ventilation system D

Regular maintenance is crucial for efficiency and lifespan. Replace filters every 3 to 6 months (depending on pollution and filter class). Have the ducts inspected and cleaned at least every 2 years to prevent mould and resistance. We offer tailored maintenance contracts: discover our maintenance service.