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Minimum Requirement Part F Fan Testing

  • Writer: RJA Electrical Services
    RJA Electrical Services
  • 2 days ago
  • 2 min read

Are You Aware?

Here are some details of the regulations changes and how they may affect you

The various ventilation systems within Part F are no longer classified between 1 and 4. It now has 3 ventilation systems:

Natural Ventilation

Previously known as system 1

Intermittent Extract Fans with background ventilators.

  • Suitable for less airtight dwellings

  • Intermittent extract fans should be fitted in all wet rooms

  • Also requires correctly sized and fitted trickle vents to be installed

  • Extraction rates remain the same as 2013 Edition


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Continuous Mechanical Extract

Previously known as system 3

A continuous mechanical extract ventilation system could consist of one of the following:

  • A central extract system known as MEV (Mechanical Extract Ventilation)

  • Individual room continuous extract fans known as dMEV (decentralised mechanical extract ventilation)

  • A combination of both MEV and dMEV

  • Also requires correctly sized and fitted trickle vents to be installed

  • Requirements for ventilation rates are measured in both boost rates and continuous rates

Minimum High (Boost) extract rates for continuous mechanical extract for each wet room.

Total Combined rate of continuous ventilation in the dwelling needs to meet the above minimum rates.


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Minimum High (Boost) extract rates for continuous mechanical extract for each wet room.


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Total Combined rate of continuous ventilation in the dwelling needs to meet the above minimum rates.


Mechanical Ventilation with Heat Recovery (MVHR)

Previously known as system 4

Mechanical Ventilation with Heat Recovery (MVHR) are whole house systems that extracts air from wet rooms whilst also supplying fresh, filtered air into habitable rooms.

Under Part F these systems:

  • Must meet the whole dwelling ventilation rates set out in Table 1.3 (above)

  • Heat Recovery minimum efficiency has increased from 70% to 73%

  • Extract air flow must match the supply air flow in order to create a balanced system

  • Must be installed by a competent person (a SAP benefit as of 2010)

  • Should have ductwork designed to minimise overall length of duct, minimise the number of bends and ensure appropriately sized duct for the air flow rate

Other Ventilation types may be used – Passive Input Ventilation (PIV) or Passive stack ventilation but expert advice should be sought and it can be demonstrated to building control that they meet requirement F1 of the new regulations.


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Minimum whole dwelling ventilation has increased

A significant change to Part F is that the whole dwelling ventilation rates have been increased.

  • If a dwelling has one habitable room, a minimum ventilation rate of 13l/s should be used

  • For each additional bedroom, add 6l/s to the 13l/s minimum requirement

  • Alternatively, the whole dwelling minimum ventilation rate should be 0.3l/s per m2 of internal floor area

Commissioning checklist can be found within Appendix C of Part F.


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Testing and Commissioning

As of 15th June 2022 the following is compulsory:

  • Air flow rates of ALL mechanical ventilation fans should be tested

    This includes:

    • Intermittent Extract Fans

    • Cooker Hoods

    • Continuous extract fans

    • MEV systems

    • MVHR Systems

  • All extraction readings MUST be submitted to building control

  • A certificate stating the recorded rates MUST be left with the property owner

  • All ventilation rates should be tested using the correct UCAS accredited flow test instrument in accordance with Building Regs Part F


Commissioning checklist can be found within Appendix C of Part F.
Commissioning checklist can be found within Appendix C of Part F.
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