Approved Document F explained

What is Approved Document F?

Approved Document F is the statutory guidance for Part F (ventilation) of Schedule 1 to the Building Regulations 2010 in England, showing how to provide adequate ventilation and how to commission mechanical systems. The current 2021 edition has been in force since 15 June 2022, and a 2026 edition of Volume 1 for dwellings takes effect on 24 March 2027.

It comes in two volumes: Volume 1 for dwellings and Volume 2 for buildings other than dwellings. It covers England only. Wales publishes its own Approved Document F and has issued its own 2026 edition of Volume 1, taking effect on 4 March 2027.

The requirement itself has two parts, both short enough to know word for word:

• F1(1): "There shall be adequate means of ventilation provided for people in the building."
• F1(2): "Fixed systems for mechanical ventilation and any associated controls must be commissioned by testing and adjusting as necessary to secure that the objective referred to in sub-paragraph (1) is met."

F1(2) was added in 2021. Commissioning is now a requirement in its own right, not just good practice.

Three regulations sit alongside the Schedule 1 requirement and are covered in the same Approved Document:

Regulation 39

Within five days of completion, the person carrying out the work gives the owner enough information about the ventilation system and its maintenance, written for a non-technical reader.

Regulation 42

Mechanical ventilation air flow rates in new dwellings are tested, with results given to building control no later than five days after the final test.

Regulation 44

Commissioning notices for fixed building services go to building control within 30 days of completion.

Which edition applies in October 2026?

Three documents are live on GOV.UK. Which one applies depends on the building type and when the building control application went in.

The 2021 editions of Volume 1 and Volume 2 are both in force, with Volume 2 republished with corrections in 2022. The 2026 edition of Volume 1 was published on 24 March 2026 and revised on 8 September 2026 to correct minor errors. It comes with the Building Regulations etc. (Amendment) (England) Regulations 2026, the package that implements the Future Homes and Buildings Standards. There is no 2026 edition of Volume 2, so non-domestic projects continue to use the 2021 edition.

What changes in the 2026 edition?

The 2026 edition keeps the rates, system types and structure of the 2021 edition. According to Circular 01/2026 and the government's consultation response, the changes focus on installation quality:

• Strengthened guidance on installing and commissioning fixed building services, aligned with Approved Document L.
• Emphasis on a registered competent person scheme installer for mechanical ventilation. Non-registered installers must notify building control before work starts.
• Commissioning personnel for most mechanical systems should belong to an organisation that regularly and independently verifies their competence.
• The maximum specific fan power for continuous decentralised MEV is raised to 3.5 W/(l·s).

The government decided not to extend regulation 42 air flow testing to work in existing buildings.

How to choose a ventilation system for a dwelling

Volume 1 groups systems into three types, and the deciding factor is how airtight the dwelling will be. Natural ventilation suits less airtight dwellings only; continuous mechanical extract (MEV) and MVHR suit all dwellings.

• Natural ventilation with background ventilators and intermittent extract fans: paras 1.47–1.59.
• Continuous MEV, centralised or decentralised: paras 1.60–1.66.
• MVHR, mechanical ventilation with heat recovery: paras 1.67–1.73.

This matters at design stage. If a dwelling is designed for natural ventilation and then tests as highly airtight, the guidance gives two options: get expert advice on how Part F will be met, or install continuous mechanical extract ventilation. Retrofitting ductwork at completion is expensive, so the safer route is to agree the airtightness target with the energy assessor before fixing the ventilation strategy.

What ventilation rates Volume 1 sets

The rates in the 2026 edition of Volume 1 are the same as in the 2021 edition. Whole dwelling ventilation is the higher of a floor-area rate and a bedroom-based minimum.

• Intermittent extract: 30 l/s for a kitchen with a cooker hood extracting to outside, 60 l/s without one; 30 l/s for a utility room; 15 l/s for a bathroom; 6 l/s for sanitary accommodation.
• Continuous extract (high rate): 13 l/s kitchen, 8 l/s utility room, 8 l/s bathroom, 6 l/s sanitary accommodation.
• Purge ventilation: each habitable room should be able to extract at least four air changes per hour directly to outside, usually through openable windows sized using Table 1.4.

The guidance also gives indicative noise levels for mechanical systems: 30 dB L_Aeq,T in noise-sensitive rooms such as bedrooms and living rooms on minimum low rate, and 45 dB L_Aeq,T in less sensitive rooms. It states that noise testing is not required.

How Part F interacts with Parts L and O

Ventilation decisions sit between energy and overheating, so the three Approved Documents need to be read together. The two common traps are an airtightness figure that rules out the chosen system, and purge openings mistaken for Part O compliance.

Part L airtightness. Approved Document L Volume 1 (2021, incorporating 2023 amendments) sets a limiting air permeability of 8.0 m³/(h·m²) at 50 Pa for new dwellings. Most SAP compliance routes need far better than that, which often pushes a dwelling into the highly airtight category and rules out natural ventilation. The airtightness figure in the SAP model and the ventilation strategy need to agree.

Pollutant ingress. Section 2 of Volume 1 asks designers to limit intake of outdoor pollutants near significant sources such as busy roads. Intakes should be kept away from those sources, and exhaust outlets placed so air does not re-enter. Approved Document O points back to this section when assessing whether windows can realistically be opened.

Non-domestic buildings and work to existing dwellings

Volume 2 covers offices, schools, healthcare, shops and other non-domestic buildings, and also rooms for residential purposes such as hotels, hostels and halls of residence. Hotel rooms and halls are not dwellings in the Building Regulations, so they follow Volume 2, not Volume 1; purpose-built student flats should be checked against the definitions in the Regulations.

Two provisions introduced in 2021 still catch people out:

• Indoor air quality monitoring: in new offices, occupiable rooms should have a means of monitoring indoor air quality, for example a CO₂ monitor. Rooms up to 50 m² and over 320 m² are excluded. Appendix C notes that an average of 1,500 ppm CO₂ over the occupied period indicates poor ventilation.
• Recirculation: systems that recirculate air between spaces should be able to run in a mode that reduces the risk of airborne infection, by supplying 100% outdoor air, using UV-C in the recirculated air, or accepting HEPA filters.

For offices, the outdoor air supply rate is the higher of 10 l/s per person or 1 l/s per m² of floor area.

Existing dwellings

Part F applies when other work affects ventilation. The guidance says ventilation should meet the standard or be "not less satisfactory than before the work was carried out". Insulation and draught-proofing may reduce infiltration enough to need additional ventilation, so an assessment is needed. Volume 1 is specific about replacement windows:

• ✓Record whether the existing windows have background ventilators.
• ✓If they do, the new ones have ventilators that are no smaller and are controllable.
• ✓If they do not, specify at least 8,000 mm² for habitable rooms and kitchens and 4,000 mm² for bathrooms, or an equivalent shown to comply.
• ✓Assess whether related insulation or draught-proofing work needs extra ventilation.

Where Avoice fits

Ventilation requirements are spread across Part F, regulations 39, 42 and 44, and cross-references in Parts L and O. With two editions of Volume 1 live at once, quoting the wrong one is easy.

The Avoice Regulations library holds the full Approved Documents for England, Wales, Scotland and Northern Ireland, including both editions of ADF Volume 1, with AI search that says whether an answer comes from legislation or statutory guidance. On live projects, the Building Regs Tracker in Avoice Practice records how each Part, including F, is being met and what evidence is still outstanding.

Software can retrieve, compare and flag. The services engineer, the energy assessor, the architect and building control still decide what the project requires.