Approved Document F 2026 — published alongside Part L on 24 March 2026 — governs ventilation in new dwellings. Combined with Part L's tightened air permeability target of 3 m³/(h·m²), MVHR becomes effectively required for the majority of FHS-compliant homes.
Why MVHR becomes effectively required
At the 4.0 m³/(h·m²) notional air permeability — half the limiting value of 8.0 — natural and trickle ventilation strategies struggle to deliver adequate fresh-air rates without overventilating. MVHR (mechanical ventilation with heat recovery) extracts stale air from wet rooms, supplies fresh air to bedrooms and living rooms, and recovers ~85% of the heat from the extract air.
How MVHR integrates with the FHS spec
MVHR runs continuously on low power (~30W). Combined with the larger solar array specified for FHS, the system frequently runs on excess PV — adding to self-consumption and improving the SAP/HEM score. The fresh-air supply also supports the larger glazing areas typical of modern designs without overheating.
Cost
A typical 3-bed MVHR installation (Vent-Axia Sentinel Kinetic, Nuaire MRXBOX or Zehnder ComfoAir) installed costs £2,400–£3,200. Larger 4-bed and 5-bed systems run £2,800–£3,800. The £2,800 line item in the FHS Impact Assessment matches this range.
Commissioning and Part F requirements
Approved Document F requires post-installation commissioning with airflow measurements at every grille. Many MVHR installations fail commissioning at first attempt due to ductwork compromises during the build. Schedule MVHR commissioning before the main contractor’s handover.
Alternative ventilation strategies
Decentralised mechanical extract ventilation (dMEV) systems remain compliant on smaller dwellings where the air permeability can be brought to ~4–5 m³/(h·m²). Passive stack ventilation is now rarely viable. MVHR is the dominant new-build solution from 2027.