Decentralised Ventilation in Berlin

Central KWL supplies all rooms via a shared duct network and typically achieves 85–95 % heat recovery. Decentralised units work room by room with small individual devices (~90 cm × 25 cm × 25 cm) and achieve 70–85 % recovery via ceramic heat exchangers. Decentralised systems are significantly cheaper (€800–1,200/unit vs. €5,000–12,000 for central KWL), easier to retrofit, and have no ventilation hoses in the house. Disadvantage: lower efficiency and higher power consumption with multiple units. Particularly in Berlin old-builds, often the best compromise solution.

Decentralised units produce 25–35 dB(A) at normal operation (level 2–3 of 4) – about like quiet conversation. On level 1 they drop to 20–25 dB(A), on highest level 40–45 dB(A). The outdoor unit produces typically 40–48 dB(A) from 2 m distance. With acoustic accessories (elastic mounts, sound-damped pipes) the level can be reduced by 3–5 dB. The best solution is correct manufacturer selection and installation – some units are noticeably quieter than others.

A core-drilled hole (Ø 75–100 mm) in the outer wall requires written landlord consent and possibly homeowners' association (WEG) approval for multi-unit properties. Usually unproblematic since the installation is reversible (hole gets sealed after moving). We prepare a consent letter for the landlord and coordinate with any scaffolding or facade work. With listed building protection, planning permission from the monuments authority is required – complicates installation but is feasible.

As a rule of thumb: 1 decentralised ventilation unit per 40–60 m² living space, minimum 1 unit each for bedroom and kitchen. An 80 m² apartment typically needs 2–3 units in alternating operation (1 supply-air unit bedroom, 1 extract-air unit kitchen, possibly 1 more unit for living room). This gives total costs of €3,000–5,000 for complete coverage. Central KWL would be similarly priced but significantly more efficient. We advise based on layout and usage.

For single-family homes no permit is required. For multi-unit properties you need landlord consent (usually unproblematic) and WEG approval in larger complexes which we verify upfront. For listed buildings an authority permit is required – this can take 4–8 weeks but is usually granted. Costs for permit: €200–500. We apply for this and often can offer an alternative (e.g. surface-routed piping) if core-drilling is denied.

Theoretically yes, practically difficult – decentralised ventilation units have wall penetrations and cannot simply be 'plugged in' to central systems. If your old-build is later renovated and you want central KWL, the decentralised units must be removed and new ducts routed. Costs for this conversion about €3,000–6,000. But that's a thought for 15–20 years down the line. Today decentralised is the quickest and most cost-effective solution – you can always upgrade later.