Counterflow Decentralised HRV/ERV Products
Counterflow decentralised HRV/ERV systems, such as the Lunos Nexxt, operate using two fans and a central counterflow heat exchanger core. Unlike alternating push-pull decentralised units (with one fan per unit), which reverse direction every 40–90 seconds, these systems maintain constant two-way airflow, much like larger centralised HRV/ERV systems. One fan continuously draws in fresh outside air while the other simultaneously exhausts stale indoor air, with both air streams passing through the counterflow core. This design allows for efficient heat (and, in the case of ERV, moisture) transfer between the outgoing and incoming air, providing balanced ventilation, improved comfort, and quieter operation without creating pressure imbalances in the room.
Push-Pull Decentralised HRV/ERV Products
Smaller decentralised “push-pull” units, such as the Lunos e²60 or Stiebel Eltron VLR 70, work on a reversing cycle rather than continuous two-way flow. Each unit has a single fan and a ceramic/plastic/metal thermal accumulator. During the exhaust phase, warm stale indoor air is blown out through the core, charging it with heat (and some moisture in the case of ERV-type ceramics). After a set period — typically around 70 seconds — the fan reverses direction, drawing in fresh outdoor air. As the air passes back through the warmed core, much of the stored heat is transferred to the incoming supply air. By pairing two units to run in opposite phases, a balanced supply and extract airflow can be achieved across a dwelling, providing effective heat recovery and fresh air without the need for ductwork.
Decentralised HRV/ERV Filters
Replacement filter sets are readily available. Performance of each system can only be guaranteed with original filters.
