Ventilation system in new build: useful 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 anymore. A controlled living space ventilation reliably expels moisture, odors and stale air and supplies filtered fresh air - even when no one is at home or the windows are closed. Thanks to heat recovery, it uses a large part of the heat from the exhaust air and thus lowers the heating costs. For efficiency and passive houses it is practically part of the concept. However, whether the effort is worth it depends on the construction method, floor plan and usage.

Short answer: For the KWL there are two basic principles. The central system works with a ventilation unit and a duct network that supplies all rooms; it is particularly suitable for new builds because the ducts can be planned from the beginning and provides efficient heat recovery. The decentralized system relies on individual units in the exterior walls, does not require a duct network and can be retrofitted room by room. Central systems usually cost more to purchase, but often run quieter and more efficiently; decentralized systems convince with their simple installation. The floor plan, budget and the question of whether it is new construction or retrofitting determine which variant is suitable.

Short answer: The Building Energy Act (GEG) sets requirements for thermal protection and airtightness of new builds. To prove 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 is eliminated. The GEG does not specify a particular system but requires a coherent ventilation concept. In practice, the controlled living space ventilation is therefore the most convenient way for 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 is in the mid to upper four-digit range in 2026 depending on the execution, decentralized systems are calculated per room and are cheaper individually. In addition there is the maintenance: Filters must be replaced regularly depending on the system and environment, occasional cleaning and a specialist check maintain the efficiency and hygiene of the system. The ongoing effort is limited but is firmly part of the use and should be factored into the budget.

Short answer: Yes, a functioning ventilation system is an effective component of mold prevention. It continuously transports the moisture from cooking, showering, drying laundry and breathing away before it condenses on cool components. Especially in airtight new buildings in which window ventilation does not always occur regularly enough, the KWL significantly reduces the risk. However it does not replace structural care: thermal bridges, leaky connections or unfavorable user behavior can still cause problems. As part of a coherent overall concept the ventilation system contributes substantially to a healthy indoor climate.

Short answer: Persistent myths surround ventilation systems. It is often said that the air becomes dry – in fact the air humidity is determined mainly by the outdoor air and the setting. In winter the air can seem drier, which also happens with window ventilation and can be regulated. Equally inaccurate is the idea that windows may never be opened again: opening windows is possible at any time, it is just no longer mandatory. The fear of strong noise or unhygienic technology also does not hold with proper planning and maintenance. A good design, clean installation and regular care are decisive.