Ventilation System in a New Build: Worthwhile or Superfluous?

Short answer: In most of today’s new builds a ventilation system pays off, because the airtight building envelope hardly allows any uncontrolled air exchange. A controlled living-space ventilation reliably moves moisture, odours and stale air out and supplies filtered fresh air – even when no one is home or the windows are closed. Thanks to heat recovery it uses a large part of the heat from the exhaust air and thereby cuts heating costs. In efficiency and passive houses it is practically part of the concept. Whether the effort pays off, however, depends on the construction method, floor plan and use.

Short answer: With the KWL there are two basic principles. The central system works with one ventilation unit and a duct network that supplies all rooms; it is suitable above all for new builds because the ducts can be planned in from the outset, and it delivers efficient heat recovery. The decentralised system relies on individual units in the external walls, manages without a duct network and can be retrofitted room by room. Central systems usually cost more to purchase but often run more quietly and efficiently; decentralised systems impress with easy installation. Which variant suits is decided by the floor plan, budget and the question of whether it is a new build or a retrofit.

Short answer: The Building Energy Act (Gebäudeenergiegesetz, GEG) sets requirements for the thermal protection and airtightness of new builds. To demonstrate these, a blower-door test is often used: the house is put under positive and negative pressure to determine the tightness of the building envelope. The tighter the building, the more important a planned ventilation becomes, because the natural air exchange no longer happens. The GEG does not prescribe a specific system but requires a coherent ventilation concept. In practice, controlled living-space ventilation is therefore the most convenient way in many new builds to keep moisture and air quality safely under control.

Short answer: The costs depend on the system, house size and installation effort and can only be quantified as a range. A central KWL with heat recovery for a single-family house moves, in 2026 depending on the version, in the mid to upper four-figure range; decentralised systems are charged per room and are cheaper individually. Added to this is maintenance: filters must be changed regularly depending on the system and environment, and an occasional cleaning and a specialist check preserve the efficiency and hygiene of the system. The ongoing effort stays within limits but firmly belongs to the use and should be factored into the budget.

Short answer: Yes, a functioning ventilation system is an effective building block of mould prevention. It continuously transports away the moisture from cooking, showering, drying laundry and breathing before it condenses on cool components. Especially in airtight new builds, where window airing does not always happen regularly enough, the KWL reduces the risk considerably. It does not, however, replace structural care: thermal bridges, leaky connections or unfavourable user behaviour can still cause problems. As part of a coherent overall concept, however, the ventilation system contributes significantly to a healthy indoor climate.

Short answer: Stubborn myths persist about ventilation systems. It is often said the air becomes dry – in fact the humidity is determined above all by the outside air and the setting; in winter the air can feel drier, which likewise happens with window airing and can be regulated. Equally untrue is the notion that you may never open the windows again: opening windows is possible at any time, just no longer mandatory. The fear of strong noise development or unhygienic technology also does not come true with professional planning and maintenance. What is decisive is a good design, a clean installation and regular care.