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Decentralized Heat Recovery — How It Works and When To Choose It

Decentralized heat recovery units ventilate individual rooms without any ductwork. They're installed directly into an exterior wall and recover up to 93% of heat — making them the go-to solution for apartments, renovations, and homes where central ductwork isn't feasible.

6 min read Updated February 2026
Modern apartment interior with decentralized ventilation
The principle

How does decentralized heat recovery work?

A decentralized heat recovery unit is a compact, wall-mounted device that provides ventilation for a single room. It's installed through a core hole (typically 160 mm diameter) in an exterior wall. Inside the unit, a ceramic or aluminium heat exchanger stores warmth from outgoing air and releases it to incoming fresh air.

Most units operate in alternating cycles: the fan blows stale air out for 70 seconds while the heat exchanger absorbs warmth, then reverses to draw fresh air in — which is pre-heated by the stored thermal energy. This push-pull cycle achieves up to 93% heat recovery efficiency.

For balanced ventilation, units are typically installed in pairs — one exhausting while the other is supplying, ensuring continuous airflow in the room.

Why choose it

Advantages of decentralized heat recovery

No ductwork required

Installation needs only a single wall core hole per unit — no ceiling voids, no duct runs, no major construction work.

Fast installation

A single unit can be installed in 2–3 hours. An entire apartment can be equipped in a single day with no disruption to other rooms.

Ideal for renovations

The perfect retrofit solution — add heat recovery to an existing building without tearing open walls or ceilings for ductwork.

Lower upfront cost

€400–1,200 per unit vs €3,000–8,000 for a central system. You can start with one room and expand gradually.

Room-by-room control

Each unit operates independently — adjust ventilation speed, set timers, or turn off rooms not in use.

Whisper-quiet operation

Modern units operate at 19–26 dB(A) on low speed — comparable to a quiet library. Ideal for bedrooms.

Modern bright room with fresh ventilated air
Decentralized units provide fresh air room by room — with no ductwork needed
Trade-offs

Limitations to consider

  • One unit per room — Each room needs its own unit (or pair), which means multiple wall penetrations for a whole house.
  • Visible in the room — The interior cover is typically 20–30 cm wide, mounted on the wall. Some homeowners prefer the invisibility of central duct outlets.
  • Slightly lower efficiency — Up to 93% heat recovery vs up to 95% for the best central units, though the real-world difference is marginal.
  • Limited air filtration options — Most units use G3/G4 filters. Central systems can accommodate higher-grade HEPA filters more easily.
  • Not ideal for very large homes — A house with 8+ rooms may benefit more from a single central system than 8+ individual units in terms of maintenance.
Best suited for

When to choose decentralized heat recovery

Decentralized heat recovery is the right choice when:

  • You live in an apartment — No access to common ductwork? Individual wall units solve ventilation room by room.
  • You're renovating an existing home — Adding ductwork to a finished building is expensive and disruptive. Wall-mounted units are the practical alternative.
  • You want to start small — Install in the most critical rooms first (bedrooms, living room) and expand later as budget allows.
  • Construction is already finished — Missed the opportunity to install ducts during building? Decentralized units can be added at any time.
  • You need room-by-room control — Different rooms, different needs. Each unit can be independently configured.

For a broader comparison of your options, see our complete guide to heat recovery or our guide to choosing heat recovery for your home.

FAQ

Frequently asked questions

As a rule of thumb: one unit per living/sleeping room, plus one in the kitchen area. A typical 3-room apartment (living room + 2 bedrooms) needs 3–4 units. Bathrooms usually don't need a heat recovery unit — a simple exhaust fan is sufficient there.
No, when properly installed. The wall sleeve is insulated, and when the unit is off, motorised dampers close the opening completely. There is no thermal bridge or air leakage in standby mode. The 160 mm core hole is sealed around the sleeve with expanding foam.
The electrical connection is simple (standard outlet), but drilling the 160 mm core hole through an exterior wall requires a core drill and knowledge of the wall structure (to avoid reinforcement, pipes, etc.). We recommend professional installation for the drilling, which typically costs €100–200 per unit. The unit itself just slides into the sleeve.
Users consistently report three main benefits: noticeably better air quality (especially in bedrooms), elimination of window condensation, and surprisingly quiet operation. The most common concern before installation is the wall hole — but after installation, most users wish they'd done it sooner. Energy savings of 20–35% on heating bills are typical in well-insulated homes.
Every 3–6 months, pull out the filter and rinse it under running water (or vacuum it). The ceramic heat exchanger can be cleaned once a year with warm water. No special tools needed — maintenance takes 5 minutes per unit. Filter replacement cost is minimal (€5–15 per filter).

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