MVHR vs Extract Fans — Ventilation Compared

A full MVHR system typically costs £3,000-5,000 installed for a 3-bed house, including the unit, ductwork, diffusers and commissioning. By contrast, individual extract fans for a kitchen, bathroom and en-suite cost £200-500 total installed. The payback for MVHR comes from reduced heating bills through heat recovery.

Modern MVHR units recover 85-95% of the heat from extracted air. In a well-insulated home (e.g. fabric-first design or Passivhaus), this can save £200-400 per year on heating bills. However, in a draughty older property, the recovered heat is offset by uncontrolled air leakage, reducing the benefit significantly.

MVHR works best in airtight buildings (below 3 m³/h/m² at 50 Pa). For buildings with air permeability above 5 m³/h/m², intermittent or continuous extract fans (System 1 or 3 per Approved Document F) are more practical and cost-effective. Most existing UK housing stock suits extract fans unless undergoing deep retrofit.

MVHR filters need replacing every 6-12 months (£20-40 per set), the heat exchanger needs annual cleaning, and ductwork should be inspected every 5 years. Extract fans need occasional cleaning and replacement every 8-12 years. MVHR has notably higher ongoing maintenance requirements.

It is possible but challenging and expensive. Retrofitting MVHR requires routing large-diameter ductwork (typically 125-150mm) to every habitable room and wet room, usually through ceiling voids or bulkheads. A retrofit typically costs £5,000-8,000. Decentralised MVHR units (wall-mounted) are an easier retrofit option at £300-600 per room.