Approved Document F sets out the minimum requirements for ventilation in residential buildings across England and Wales. It ensures that homes provide adequate airflow to maintain indoor air quality and protect the building fabric. The document applies to new builds and certain types of work in existing dwellings, covering how ventilation systems should be designed, installed and assessed to meet regulatory standards.

This guide explains the key principles, requirements and system types defined within Approved Document F, along with the latest updates and how they apply in practice. Understanding these requirements is essential for achieving compliance and delivering healthy indoor environments.

Key points

Approved Document F sets ventilation requirements for residential buildings, ensuring adequate airflow to maintain indoor air quality and protect the building fabric.
F1(1), the core requirement, states that adequate ventilation must be provided for people in the building, forming the foundation of all system design and assessment.
2026 changes to Approved Document F introduce tighter compliance and clearer guidance, including changes to implementation timelines, building control processes and ventilation system standards.
New guidance places greater emphasis on system design performance, commissioning and documentation, ensuring systems deliver consistent airflow and meet regulatory standards.
Ventilation strategies include intermittent extract fans with natural ventilation , continuous mechanical systems (MEV/d-MEV) and MVHR, each with specific performance requirements.
Ductwork and installation standards have been strengthened, with clearer rules on materials, duct lengths, insulation and system efficiency.
Commissioning is mandatory for all relevant systems, requiring airflow testing, system balancing and formal sign-off to demonstrate compliance.
Updated guidance introduces performance-based ventilation, focusing on real-world control of moisture, pollutants and indoor air quality.
Alternative solutions such as PIV, SRHR and PSV may be used where they meet Approved Document F performance requirements. The document only shows the most common ventilation solutions.

What is Approved Document F?

Approved Document F is an official document that guides on meeting the ventilation requirements of Part F of the Building Regulations.

Its core purpose is to ensure that ventilation systems are designed and installed to prevent the build-up of moisture and maintain healthy indoor environments. If ventilation is inadequate, condensation and poor air quality can negatively affect the health and wellbeing of occupants and damage the building fabric.

In both England and Wales, Approved Document F for Means of Ventilation (Volume 1: Dwellings) has one key, overarching requirement known as F1(1) stating that:

“There shall be adequate ventilation provided for people in the building."

What Are the Key Changes to Approved Document F in 2026?

Approved Document F has undergone updates for England and Wales, with the 2026 changes focusing on tighter compliance, clearer system design standards and improved installation guidance.

These updates are designed to ensure ventilation systems deliver consistent indoor air quality while aligning with modern building performance requirements, including more airtight dwellings and evolving construction practices.

Understanding these updates is essential for developers, designers and installers to ensure full compliance with current and upcoming regulations.

Implementation Dates

In England, there is a split introduction of the uplifted regulations depending on the building type. These come into force on:

24 March 2027 for works 'not in connection with higher-risk building work'.
24 September 2027 for 'building work that is in connection with higher-risk building work'.

This is outside of any works under transitional protection.

In Wales, there is a single implementation date, which is 4 March 2027, again except for works outside of the transitional protection.

Building Control and Notifications

There have been changes to the building control bodies for notification. This should either be to a local authority via Registered Building Control Approvers or Registered Building Inspectors, in line with the Manual to the Building Regulations. Sending to the regulator as an option has been removed.

Key Technical Regulations

Noise and maintenance requirements

Noise and access for maintenance sections have moved and are now further down into the main section. This includes the change of description of mechanical ventilation (in trickle/background mode) from being 'not overly noisy' to 'not unduly noisy'.

For maintenance, there has been an amendment to provide access for the general maintenance of the plant and ductwork rather than just for cleaning ductwork.

Noise consideration (Wales)

In Wales, a note has been added relating to noise levels. When locations and proximities of open windows are designed, noise-related guidelines and interactions with Approved Document F should be considered when it comes to noise from other buildings or external noise.Ventilating through adjacent rooms

Previously, when ventilating one room through another room, there should be a permanent opening. However, this no longer applies to conservatories, which are now required to be thermally separated from the rest of the dwelling.

Air permeability definitions

In relation to air permeability, the definition for 'all dwellings' has been expanded to cover both less airtight and highly airtight dwellings.

The descriptor points relating to a ‘design air permeability higher than 5m3/(h·m2) at 50Pa’ and an ‘as-built air permeability higher than 3m3/(h·m2) at 50Pa’ have been removed.

Ventilation Systems & Product Requirements

Descriptors regarding the use of centralised and de-centralised continuous mechanical extract fans (d-MEV) are established, as well as the ability to upgrade an intermittent extract fan with a d-MEV where appropriate.

Ventilation system installations should meet specific design requirements for the total dwelling airflow rates and distributed airflow rates for each room in the dwelling. These rates are typically found on a system design. If you need help with the ventilation system design for your project, find out more about envirovent’s design service.

A section has been added directed at manufacturers and suppliers of MVHR units, specifying that these should not require the use of tools or removal of the unit's main front cover to access the filters.

Ductwork and Installation Standards

The existing ducting section has been overhauled, with numerous changes now in place. These are:

Approved Duct Types

Rigid or smooth semi-rigid ducts are to be used when installing centralised mechanical extract ventilation (c-MEV) or MVHR units.

Duct Length Requirements

There is a maximum ducting length of 2m for intermittent and d-MEV fans, where practical.

If the ducting exceeds 2m for these fan types, design calculations and drawings are to be submitted to building control as proof that the system can achieve the required airflow rates and should be provided by a competent person. These should also minimise static pressure.

Flexible Ducting Requirements

Flexible ductwork is limited to 200mm and only to be used for final connections when installing c-MEV and MVHR systems. The full internal diameter is to be maintained and flow resistance within the duct minimised.

If a constant pressure system is being installed, flexible ducting is not permitted in any part of the system.

Static Pressure Requirements

All ventilation options 'should be designed and installed to minimise the system static pressure within the system' through minimising duct lengths, the number of bends/offsets and using appropriately sized ducting for the airflow rate.

When installing c-MEV and MVHR systems, there is a cap on the maximum design static pressure for ductwork installations. The capped levels are based upon the unit type and airflow rates.

Insulation Standards

Supply/exhaust insulation in conditioned areas (or a heated part of a dwelling) should be provided with the equivalent of at least 50mm of a material having a thermal conductivity of ≤0.04W(m·K).

This is in addition to the 25mm at the same thermal conductivity in unheated areas. These should be fully vapour-sealed to minimise condensation risk, and the historic use of open materials is no longer accepted.

Duct Connections and Sealing

Duct connections are to be mechanically secured and adequately sealed to prevent leaks. Mechanical fastenings are to be used for flexible ducting (i.e. rigid connectors or jubilee clips).

Condensate Drainage (Wales)

In Wales only, diagrams have been added showing the correct use of condensate drainage when installing fans, both for horizontal and vertical ducting. If the condensate trap or pipe connects to foul air, then this should be waterless to prevent smells.

Handover, Documentation & Homeowner Guidance

The details surrounding the information provided to the homeowner or resident of a new-build dwelling about the installation have been strengthened in England through the introduction of R40C.

There is a handover of a home energy guide that typically contains details of the heating source, thermostats, ventilation and other services. This should be in an appropriate format and copies sent to the local authority where applicable.

In Wales, the existing requirements under this regulation remain suitable. Both digital and paper copies of the guide should also be provided.

Installation, Commissioning and Competency Under Approved Document F

There have also been several updates relating to the commissioning of ventilation units:

Higher-Risk Building (HRB) Requirements

For England specifically, as a result of the split works for HRBs, notice of where these are taking place should be given to the Regulator, including the completion certificate.

If the Regulator of the work is [JL1] [RM2] Building Control, the local authority in which the building is located should get a copy of any notices or certificates as part of the works undertaken.

Competency Requirements

The requirement for installation and commissioning competency has been made a key area of Approved Document F for both England and Wales. Commissioning should follow a set procedure, and the person carrying out the works must be ‘suitably competent’.

This can either be by 'self-certification by a registered competent person' or 'certification by a building control body', with the works also required to meet building regulations. Further details on this and the 11F (or 11W in Wales) Requirement for general competency can be found in Approved Document L.

Certification & Compliance Documentation

Once the works have been completed, the installer or registration body must give a copy of the building regulations compliance certificate to the occupier and building control body within 30 days.

Building Control Approval

In England, if the installer or those commissioning the system are not registered competent persons and the building is not a higher-risk building, the local authority should be contacted for a registered building control approver to oversee the work. If a higher-risk building, the Regulator is to be notified.

Inspection & Final Certification

The Building Control Body (BCB) will determine the inspection/testing scheduled for compliance based upon the job and installer. Notice should be given to the BCB when the works reach set stages as set out by the BCB themselves.

Once the BCB has decided that the works meet all requirements, a completion certificate or final certificate will be issued.

Commissioning Ventilation Systems Under Approved Document F

Commissioning ventilation systems under Approved Document F ensures they are correctly installed, balanced and tested to deliver the required airflow and maintain compliant indoor air quality. In practice, commissioning confirms that systems operate as designed and meet regulatory standards.

The process varies by system type but typically includes checking installation, measuring airflow, validating performance and recording results. Understanding these principles is essential for meeting Approved Document F requirements.

Natural Ventilation with Intermittent Extract Fans

When commissioning or testing a single intermittent fan in an existing dwelling, the person carrying out commissioning must be appropriately trained.

For all other types of ventilation, they 'should be a member of an organisation that regularly and independently verifies their competence, training and performance (for example, a member of a relevant competent person scheme)'.

The commissioning checks have changed and now include requirements to show compliance with the manufacturer's requirements, that there are enough fans as per Table 1.1 and that there are no abnormal noises during operation.

ENV1633_English_TABLE 1.1 (3).jpg

Mechanical Extract Ventilation (c-MEV and d-MEV) and MVHR

Several updates have been made to the commissioning and testing requirements for c-MEV, d-MEV and MVHR systems under Approved Document F. The key changes are outlined below.

1.- c-MEV and d-MEV Requirements

c-MEV and d-MEV sections have been split in relation to needing to follow manufacturer’s requirements, the number of fans, noise, controls and balancing, as well as background ventilation.

2.- MVHR Airflow Balancing

For an MVHR, the total system balance between supply and extract airflow rates should be within 10% when operating in background ventilation mode.

3.- Airflow Measurement Requirements

Airflow rate measurements for continuous mechanical extract fans and continuous mechanical supply fans should be taken using a powered flow hood airflow measurement device or powered anemometer. A vane anemometer may be used as an alternative airflow measurement device for intermittent extract fans.

These airflow rate tests should be done in both trickle or background and boost rates, with the anemometer centred over the fan/terminal for a minimum of 10 seconds. The anemometer needs to be calibrated across a range of flow rates from at least 4l/s through to the maximum design airflow rate for the ventilation system being measured.

4.- Continuous Ventilation Commissioning Updates

For the different types of continuous ventilation and specific commissioning, there have also been updates to terminology, and some have been removed. This includes instructions for constant volume, units including duct or flow dampers and units with full variable speed controls.

5.- MVHR Summer Bypass Testing

For an MVHR unit, the automatic control of summer bypass functions should be tested as per manufacturer’s instructions.

6.- Final Commissioning Requirements

Once the unit is appropriately set up and any adjustments made, the final commissioned setting should be confirmed on the controls. These rates should be tested and recorded. Any adjustable terminals, including ceiling diffusers, should be tightened and locked off to prevent misuse.

7.- When Full Commissioning Procedures Apply

When it comes to commissioning and testing units within existing dwellings, the full commissioning procedures within Approved Document F should be followed in the following scenarios:

Where there are new centralised MEV or MVHR systems, or major changes to existing systems.
There are new mechanical ventilation fans with ductwork lengths greater than 2m in length.
There are new mechanical ventilation fans connected to ductwork with more than one 90-degree offset.

8.- Appendix C Commissioning Sheet Updates

In Appendix C, there are now six sections of commissioning sheets as opposed to the previous four. Part 3 has been split into 3a for recording details of intermittent fans, 3b for d-MEV fan details and 3c for recording centralised MEV (c-MEV) details.

Previous and 2022 Interim Key Changes to Approved Document F

From June 2022 for England, Approved Document F: Ventilation (ADF) was published in two volumes:

Volume 1: Dwellings
Volume 2: Buildings Other Than Dwellings

In Wales, as of October 2022, Volume 1: Dwellings was released. Consultations relating to the production of Volume 2: Buildings Other Than Dwellings were progressed and came into force on 29 March 2023.

For an existing dwelling, any building work (adding a room, replacing parts of a ventilation system) should meet the relevant standards of ADF. Where any energy efficiency standards are to be carried out in a dwelling, PAS 2035 is considered an adequate means of demonstrating compliance for meeting the F1(1) requirement for existing dwellings.

When inserting a new internal wall, care should be taken not to make any other matters, such as ventilation, worse. If a new room is being created as a result of the addition of an internal wall, then care should also be taken to ensure that the existing room is ventilated adequately. The general rules for ventilating a room are:

Purge

This is achieved by opening the window. A system for purge should be provided for each habitable room and should be capable of achieving 4 ACH (Air Changes per Hour) directly to outside.

If a wet room (kitchen/utility/bathroom/WC/ensuite) has no external walls and an intermittent extract fan is being used, the fan should extract at 4 ACH to provide purge ventilation. (To demonstrate compliance with Part O of building regulations for overheating mitigation, a higher purge rate than 4 ACH may be required.)

As an alternative for sanitary accommodation, the purge ventilation guidance may be used within Table 1.1, Note 3 of Approved Document F.

Infiltration

Infiltration is an uncontrollable air exchange between the inside and outside of a building. This is generally through gaps, cracks and openings in a building. For older buildings that are typically leaky in terms of air permeability, the infiltration levels are higher than in a modern new build or retrofit.

This is in contrast to purpose-provided ventilation, which is a controlled exchange of air between the inside and outside of a building.

What are the Main Ventilation Strategies Under Approved Document F?

Approved Document F: Volume 1: Dwellings looks at different strategies for ventilation. The performance rates for each of the ventilation approaches are the minimum requirements needed to ensure adequate air quality is provided for people indoors.

The following systems are outlined which satisfy the performance standard. The former numbering of Systems 1-4 has ceased.

Natural Ventilation (Background Ventilation & Intermittent Extract Fans)

This ventilation option was previously referred to as Intermittent Extract Fans and Background Ventilation and involves an intermittent extract fan which is often used only when required during cooking and bathing. These are individual and found in wet rooms.

Given their intermittent nature, background ventilation such as trickle vents, which can be incorporated into the head of the window framework or by other means, are required. The requirements for natural ventilation with background ventilation and intermittent extract fans are seen below in Tables 1.1 and 1.7 and vary depending on the room being served.

ENV1633_English_TABLE 1.1 (3).jpg

ENV1633_English_TABLE 1.7.jpg

Approved Document F Requirements

To meet the requirements of this ventilation system in Approved Document F, intermittent extract fans with background ventilation (i.e. trickle vents in the windows) will need to be installed. The extractor fans are located in wet rooms, including the bathroom, en-suite, kitchen and utility room. These fans must comply with intermittent airflow rates as per Approved Document F as well as the total background ventilator area in mm2.

envirovent offers the Silent, Classic, Profile and EBB fan ranges that are intermittent, as well as the Silent MV inline fan ranges.

Understanding Background Ventilation

Background ventilation allows the introduction of fresh outside air into a room without opening a window. The purpose is to remove stale indoor air and replace it with fresh outside air. These often take the form of trickle vents in windows, through-wall vents or through natural leakage and infiltration.

The intermittent airflow rates and background ventilation requirements can be found in Approved Document F in Tables 1.1 and 1.7.

ENV1633_English_TABLE 1.1 (3).jpg

ENV1633_English_TABLE 1.7.jpg

Airtightness Requirements

It is also important to note that natural ventilation with intermittent fans and background ventilators is only recommended as a ventilation solution for use in less airtight dwellings with a design air permeability of greater than 5m3/(h.m2)@50Pa.

If there are any doubts on this, contact the specialist undertaking the airtightness test or the architect that determined the figure.

Fan Controls and Maintenance

These intermittent extractor fans can be operated with different control functions, including with a light switch, remote cable, pullcord, humidistat, PIR (presence detector) or timer.

These fans may also not be the most energy-efficient solution due to their need to power on and off fully when required, against a continuously running fan that runs at low speed in the background before being boosted when required.

In addition, if they are not switched on, the property is not being adequately ventilated. The fans must be regularly maintained to work effectively and minimise sound levels.

Continuous Mechanical Extract Ventilation (MEV & d-MEV)

Continuous mechanical extract ventilation (MEV) can be either a whole house centralised MEV system, or localised decentralised MEV (d-MEV) fan, such as envirovent's MEV 160, MEV 300, Infinity 8 and QURO®-LC fans.

Continuous mechanical extract systems typically either have integral controls, including built-in humidity sensors, as well as optional usage sensors and wireless speed controllers.

How MEV Systems Work

A centralised continuous MEV system is typically located in a loft space or hallway cupboard to run centrally within the property. Multiple ducts run from the unit to the kitchen, bathroom, en-suites and other wet rooms of a property to simultaneously draw moisture-laden air from these wet rooms to control humidity levels and expel to atmosphere.

Decentralised continuous MEV (d-MEV) fans are individually located within each wet room. These operate continuously to draw moisture from either the bathroom, kitchen, utility room or WC.

Approved Document F Ventilation Rates

The minimum extract rates for continuous extract systems are shown in Table 1.2 (Boost rate) of Approved Document F. The minimum whole dwelling ventilation rates by the number of bedrooms are also shown in Table 1.3 (trickle rate for the whole dwelling).

ENV1633_English_TABLE 1.2.jpg

ENV1633_English_TABLE 1.3.jpg

Background Ventilation Requirements

Background ventilators are required for Continuous Mechanical Extract Ventilation. However, these are at a much lower level than with intermittent fans, as these fans are continuously running. These should not be in wet rooms and are to provide a minimum equivalent area of 4000mm² for each habitable room. The minimum total number of background ventilators must equal the number of bedrooms plus two additional background ventilators.

Mechanical Ventilation with Heat Recovery (MVHR)

Mechanical Ventilation with Heat Recovery (MVHR) extracts stale, moist air out of the wet rooms of a property, typically via a centralised system. However, the heat is retained within a heat cell in the centre of the unit.

External filtered air is simultaneously supplied into the habitable spaces (living rooms, bedrooms, etc.), taking the retained heat back into the property, which helps to reduce heating costs.

Features and Benefits

MVHR systems include a variety of features, including enhanced speed controls, frost protection, a summer bypass for periods of hot weather, constant volume technology and increased filtration. They are also the mandatory ventilation solution for Passivhaus compliance.

envirovent’s energiSava® 260 and Slimline 300 are examples of MVHR systems.

Approved Document F Ventilation Requirements

MVHR systems should always provide the minimum whole building ventilation rate seen within Table 1.3, which is the trickle or background rate.

Due to the ability of the MVHR unit to extract stale, moist air and supply fresh, filtered air into the dwelling, there is no requirement for background ventilation. This ventilation solution works particularly well if there are acoustic, pollution or overheating concerns.

ENV1633_English_TABLE 1.3.jpg

Alternative Ventilation Strategies Under Approved Document F

Alongside the most common ventilation strategies, Approved Document F also considers other options to be acceptable, provided they meet the requirement F1(1), including the airflows listed within the documents.

Positive Input Ventilation (PIV)

PIV units are sophisticated, whole house ventilation systems usually located within a loft space where appropriate. If installed in an apartment, then wall-mounted units are also available. envirovent offers the ATMOS® range, as well as the AirSource and Inline units for a variety of different specifications.

The loft-mounted units take air that naturally enters the loft space, which is slightly warmer thanks to solar gain, and positively pushes the air into a central area of the property, which is usually the landing ceiling, via a diffuser. Thanks to the positive pressure, this dilutes, displaces and replaces stale, moisture-laden air with filtered air to control condensation and mould growth. Wall-mounted units are available that bring air in from outside the apartment or a building with a low roof apex before positively pushing the airflow around the dwelling.

PIV System Variations

There are several types of PIV available, from standardised units, with integral speed controls to meet the different requirements of a property, to wireless or app variants. AirSource units provide a permanent ducting feed to the exterior of a property for specific targeted areas and where there are high levels of Radon.

Background Ventilation Requirements

Background ventilation may be required, but this depends on the air permeability of the property, as PIV needs a good crossflow of air to work effectively and to replace and renew the air.

Generally, if air permeability is tighter than 3m3/(h.m2)@50Pa, there is a requirement for background ventilation.

Supplementary Extract Fan Requirements

Depending upon the property layout, supplementary fans may not be required in each wet room, as the PIV unit will cover each wet room directly off the landing/hallway from where the diffuser is located.

For remote wet rooms, which are those in which you need to walk through a room between the hallway/landing to access (i.e. an en-suite within a bedroom or a kitchen that is located through a living room in a separate space), there is a requirement for supplementary continuously running extractor fans.

Although there is no standardised requirement for extract fans directly off the hallway or landing, these are often installed as good practice to assist the PIV unit and help ventilation rates of the whole house.

Installation Benefits and Applications

PIV ventilation is a whole house, year-round system that also has the benefit of being suitable for retrofit properties. Little additional works are required for installation and, most often, no duct runs.

Even for AirSource units, these require a single duct run to atmosphere within the loft space, so again these do not require significant works.

Most PIV units come with a form of heater to temper the incoming air in colder months and benefit from increased filtration, as with envirovent’s ATMOS and other PIV systems.

Single Room Heat Recovery (SRHR)

Single Room Heat Recovery, or SRHR, is a localised form of MVHR, such as envirovent's heatSava® range. Often installed through the wall in a wet room, these provide both extract and supply ventilation, whilst recovering some of the energy that would normally be lost through extraction.

Some solutions are also ducted, but generally these are best installed through the wall and can have two motors similar to an MVHR unit. There are alternative units known as push-pull, extracting for a set period and then supplying air for a set period, often with a ceramic heat exchanger in the centre.

Passive Stack Ventilation (PSV)

Passive Stack Ventilation or PSV is a natural ventilation solution relying upon buoyancy and wind.

Ducts are located in wet rooms such as kitchens and bathrooms that run up to the roof ridge, or height of the ridge. These can have up to two 45-degree bends to reach the required heights, but do not have any mechanical solutions within the ducts.

This is quite a niche ventilation option and comes with specific stipulations regarding the location and height of the building due to the reliance on wind and buoyancy.

As with natural ventilation with intermittent extract fans, background ventilation is required if using this ventilation solution.

Compliance and Commissioning Under Approved Document F

Compliance with Approved Document F ensures ventilation systems meet the required standards. Systems must be properly commissioned, tested and signed off to confirm they deliver adequate airflow and indoor air quality.

Recent updates place greater emphasis on demonstrating compliance through documented checks and full system commissioning, rather than partial sampling. Alongside this, performance-based approaches focus on how effectively a system controls moisture and indoor pollutants in real conditions.

Together, these elements define how ventilation systems are assessed against regulatory requirements and long-term performance expectations.

Compliance Requirements

Within the updated Approved Document F, there is greater focus on compliance and commissioning, with elements from the previous Domestic Ventilation Compliance Guide (DVCG) now amalgamated into Approved Document F.

When commissioning new-build dwellings, all properties must be fully commissioned, not just a set percentage. There is a new commissioning checklist for the system declarations, inspection and commissioning. As well as this, there is now a checklist for commissioning units within existing properties included for retrofit works.

Ventilation is a controlled service, in a similar way to gas and electrical work. Building Control must be notified on completion of works if the installer is not part of a competent persons scheme.

Performance-Based Ventilation

Within Appendix B of ADF: Volume 1 is a section on performance-based ventilation and the criteria to meet this standard. There is a further table showing guidance values for indoor air pollutants.

This section looks at the control of moisture levels, indoor pollutants (VOCs) and harmful chemicals. It provides infiltration levels dependent on the air permeability linked to the performance-based ventilation. This area is set to be broadened in the future by Public Health England and other specialist teams.

Get Expert Ventilation Design Support with envirovent

Approved Document F sets the standards needed to ensure ventilation systems deliver safe, compliant indoor air quality. By applying its principles and requirements, developers and installers can design and assess systems that meet regulatory obligations while supporting healthier, more durable buildings.

If you need support with ventilation system design, envirovent's specialist team can help simplify compliance and ensure your project meets current regulations. Our experts provide detailed, compliant system designs tailored to your development, helping you achieve the required standards efficiently and with confidence.

Feel free to get in touch with our team for a consultation.

Approved Document F Building Regulations