Changes to Building Regulations, Part F Ventilation

The current Building Regulations Part F, which covers ventilation, has been in place since 2010 but over the years key issues have been identified and concerns voiced over the failure of homes to comply.  Furthermore, new guidance from Public Health England on selected VOCs indoors and World Health Organisation (WHO) recommendations for indoor pollutant levels have meant Part F, as it stands, is out of date.

‘The Future Homes Standard: changes to Part L and Part F of the Building Regulations for new dwellings’ consultation, which closed in February of this year, is the first stage of a two-part consultation about proposed changes to the Building Regulations.  The consultation sets out the government’s plans for the Future Homes Standard, which will be introduced by 2025, and focuses on increasing the energy efficiency requirements for new homes.  This is one of the measures being taken to reduce all greenhouse gas emissions to net zero by 2050, which has been set in law.  The expectation is that an average home will have 75-80% less carbon emissions than one built to current energy efficiency requirements, so it’s a big leap and will require big changes.

Increased Ventilation

Part L (Conservation of fuel and power) and Part F of Building Regulations are very closely linked.  If we are to achieve the type of low energy buildings laid out in the Future Homes Standard, new homes will need to become even more airtight than they are now to reduce energy wastage. 

Without sufficient ventilation though, these homes can become overheated and the air uncomfortable and unhealthy to breath.  Consequently, Part F will also need to change to ensure the right level of ventilation is supplied to ensure good indoor air quality and user comfort.  And that change means increasing the level of ventilation.

Mechanical ventilation, in the form of intermittent extract, continuous extract (MEV systems) or supply & extract (MVHR systems), are recognised as the most proficient means of ventilating a modern property.  The revised Building Regulations are expected to increase the minimum airflow through these systems to each bedroom by 6 l/s.  This has been introduced in concern over insufficient ventilation in bedrooms overnight if doors are kept shut.  The other expected change here is an increase in the background ventilation from 2500 mm2 to 5000 mm2 in extract-only systems.

Natural ventilation systems, i.e. background ventilation, will remain an option under the new regulations, but only for less airtight homes with a design air permeability of ≥ 5.  This is disappointing as it’s not an energy efficient way of ventilating a home as natural heat will be lost to the outside whilst there is no guarantee of moisture or pollutants migrating outside.  If housebuilders aren’t put off by this and are still considering relying on natural ventilation, then hopefully they may be put of by the likely requirement for much larger grilles which are far from aesthetically pleasing.  That’s because the revised regulations require the size of the background ventilation grille to be determined on a room by room basis, rather than based on the whole property.

One expected change in the new regulations that has surprised a number of people is the removal of Positive Input Ventilation (PIV) as an alternative approach.  Whilst MEV and MVHR remain the better option, PIV can provide a good solution in new build applications where ducted systems are difficult to incorporate into the build.  However, Approved Document F 2020 does make allowance for other systems, such as PIV, ‘provided it can be demonstrated to the building control body that they meet Requirement F1(1)’; a BBA Certificate supplied by the manufacturer will suffice here.

Simplification of the Regulations

A number of studies, including the government’s ‘Ventilation and indoor air quality in new homes’ paper, have shown a large proportion of homes simply do not comply with the current Building Regulations requirements and poor indoor air quality has been observed in several sample homes tested.  So, Building Regulations are either being flouted or are not being understood and implemented. This is something we identified a number of years ago and launched a Domestic Ventilation Installer training course in partnership with BPEC, which is a recognised qualification for relevant Competent Person Schemes. 

Clearly, if Building Regulations are being deliberately ignored then action needs to be taken to address this through Building Control.  However, feedback from industry and building inspectors has indicated that what’s more likely is confusion and a lack of understanding of the regulations leading to failure to comply.  They have expressed a need for simplified guidance, which would assist designers and help with inspections and sign off. 

The result is a simplification of ventilation standards in relation to a property’s air permeability through the recommended use of continuous Mechanical Extract Ventilation (MEV) and continuous supply & extract ventilation (e.g. Mechanical Ventilation with Heat Recovery – MVHR) for properties with any level of air tightness.  Furthermore, whole house ventilation design calculations, will now only require the number of bedrooms and floor area to be taken into consideration, removing the need to predict occupancy rates, which removes guess work. 

For some, the changes to Parts L and F of the Building Regulations don’t go far enough in reducing carbon emissions and energy consumption.  For now though, these changes are heading your way and, when it comes to ventilation, it’s a carrot and stick approach: it’s easier to understand and implement, as the industry has asked; but ventilation rates are increasing and you must supply a copy of the checklist and commissioning sheet to the building owner to prove you’ve done what is required of you. 

Domus Ventilation is a manufacturer of market-leading ventilation systems that save energy and improve indoor air quality.

Revised Building Regulations Part F: what you should be doing differently and why

The world is a very different place since 2010, the year that Building Regulations ‘Ventilation: Approved Document F’ was previously revised.  In the years that have elapsed we have not only learnt considerably more about Indoor Air Quality (IAQ), and pollutants and their impact on our health, but we have also had to contend with a pandemic that has changed our relationship with our home environment.

During this timeframe, albeit more recently, the drive towards the 2050 Net Zero goal has become more intense.  To reduce emissions as close to zero as possible, we must decarbonise all sectors of the UK economy, including housebuilding.  The Future Homes Standard, which will be introduced by 2025, is the housing sector’s strategy to achieve this.  It requires new homes to be considerably more energy efficient, with average homes having 80% less carbon emissions than those built to current energy efficiency requirements.  Building Regulations is the method being used to achieve the Future Homes Standard.

Set amongst this context, it is without doubt that Building Regulations Part L (Conservation of fuel and power) and Part F were ripe for an update.  After some delay, these were published in December 2021.  The aim is to ensure new homes built from 2022 produce 31% less carbon emissions compared to current standards.  A further revision will take place to come into force in 2025 to bring that figure to the 80% reduction.

Who Needs to Comply?

If a building notice, initial notice, or full plans for building work have been submitted to a local authority before 15th June 2022 and the building work commences by the same date the following year, the new standards do not apply. For building works after those key dates, the revised Part L and Part F must be followed. 

Furthermore, there are no exemptions based on the size of the new build.  Under the previous Regulations, smaller developments were exempt from air tightness testing.  Now, air tightness testing is mandatory in all new build dwellings.  So, when it comes to Part F, all new dwellings have to comply with this aspect.  This is necessary if we are to produce the type of airtight low energy buildings laid out in the Future Homes Standard. 

But of course, the more air tight we make our homes, the greater the need for sufficient ventilation to maintain a healthy and comfortable atmosphere.  The revisions to Part F are a direct response to this requirement.  So, what has changed?

Mechanical Ventilation Systems

Mechanical ventilation systems in the form of Mechanical Extract Ventilation (MEV) and Mechanical Ventilation with Heat Recovery (MVHR) are recognised in Building Regulations as the most proficient means of ventilating a dwelling.  To ensure incoming air reaches all parts of a home – especially the bedrooms – the minimum ventilation rates have been increased as follows:

No. bedroomsPrevious min. ventilation rate l/sNew min. ventilation rate l/s

For larger properties, this increase is substantial and will mean choosing mechanical systems with greater fan power.

In a much welcomed move, predicted occupancy rates have been removed from the ventilation calculations, making them far more straightforward.

Background Ventilation

Two key changes have been introduced here. 

The first is the guidance on sizing background ventilators, including intermittent extract fans, trickle vents in windows and airbricks in the wall.  These are to be done on a room-by-room basis rather than the whole property.

The second applies to extract only systems, such as MEVs, where the background vents must be increased in size from 2500mm2 to 5000 mm2.  This may well impact on the property’s façade and window sizes.

Natural Ventilation

Natural ventilation systems, such as background vents, remain an option although only for less airtight homes with a design air permeability of ≥ 5.  However, with the background ventilation to be determined on a room by room basis, rather than based on the whole property, this will probably mean much larger grilles are required. No matter how well designed the grille is, it is likely to compromise the aesthetics of the property from both inside and out. 

Ultimately, natural ventilation isn’t an efficient means of ventilating a home as heat will be lost and there is no guarantee of moisture or pollutants migrating outside. 

The other change here is that Passive Stack Systems have been removed as an option.

Positive Input Ventilation (PIV)

Also essentially removed as a practical option under the revised regulations are PIV systems.  The only circumstance under which they can be used is if their effectiveness can be clearly demonstrated against the pollutant guidance values and criteria provided.  For the majority of people, the extra work required to do this and the uncertainty will effectively rule out PIV as an alternative to MEV and MVHR systems. 

Air Pollution Guidance

With air pollution now firmly on the news agenda, and our increasing understanding of its dangers to our health, the revised Part F addresses both internal and external air pollutants more thoroughly. 

Useful indoor air pollution guidance has been added, covering exposure limits and times for Carbon monoxide (CO), Nitrogen dioxide (NO2), Formaldehyde (CH2O) and TVOC.

In areas with high level of outdoor pollution, advice has been provided on the location of intake grilles, primarily away from the direct impact of the sources of local pollution. Where urban traffic is a source of pollution, the air intakes for dwellings next to busy urban roads should be as high as possible and located on the less polluted side of the building.  Ventilation intakes should not be located in courtyards or enclosed urban spaces where air pollutants are discharged.


With many homes unable to comply even with the previous Building Regulations Part F requirements, either through confusion and a lack of understanding of the requirements or through deliberate flouting of them, the reporting procedures have been tightened up under the 2021 revisions.

Now a new style commissioning sheet featuring a compliance report and photographic evidence must be provided to Building Control Bodies and the building owner, along with a Home User Guide specifically for householders.

So much has changed in the eleven years since Building Regulations ‘Ventilation: Approved Document F’ was last revised; some of it predictable, others out of the blue.  The changes made to Part F are both a reflection on this, but more importantly look to the future and how we as an industry can meet Net Zero and provide housing fit for purpose. 

Fire Safety in Ventilation: what’s changed?

Building Regulations Fire Safety Approved Document B has been revised and has a direct impact on ventilation systems.  Paul Williams, Domus Ventilation Product Manager, explains the new regulations and what you need to do to comply.

For those working in the ventilation sector, Part F is the go-to section of Building Regulations that you will be all too familiar with; it provides guidance on building ventilation, including building air quality and preventing condensation. 

However, it’s not the only relevant part of Building Regulations: Building Regulations Fire Safety Approved Document B should be a vital piece in your jigsaw when it comes to understanding, designing and installing a ventilation system in a domestic property.  Under Document B, where holes are made in a compartment wall for plastic ventilation ducting to pass through, those walls need to be fire-stopped to restore the walls’ fire rating.  There are a range of methods to achieve this, but dedicated products made from intumescent material are by far the best option and the easiest to install.  Domus, for example, offers a full range of Fire Sleeves and Fire Collars tested to BSEN 1366-3: 2009. 

Post Grenfell, Building Regulations came under close scrutiny, looking at all aspects of fire safety, including ventilation products and systems.  Now, Fire Safety Approved Document B has been revised with one specific important change for those in ventilation that came into force in November 2020: “Ductwork penetrating through the external cavity including termination to be non-combustible” when above 18m in England and 11m in Scotland.

What does this mean in practice?  It means using air bricks made of plastic is no longer an option above those heights.

An air brick is a basic, but important part of a building’s ventilation, as it allows fresh air to enter the property, helping to keep it cooler and reducing humidity which can lead to condensation and mould.  Air bricks can be used passively, i.e. in a standalone capacity, or with a mechanical ventilation system where they are connected to ducting to assist the air flow both in and out of the premises.

Most air bricks are made from plastic, but plastic is combustible and can contribute to a fire.  The compliant alternative is to use an air brick made from non-combustible metal.  We have introduced the Solis Air Brick™ range of low resistance, non-combustible metal air bricks that are fully compliant with the revised Building Regulations Fire Safety Approved Document B. They are made from 1.5mm galvanized steel (fire class A1) non-combustible material are suitable for use with all external wall types. 

In England, you can continue to use plastic air bricks below the 18m mark, but we would urge you to think twice before doing this and consider the safety of the inhabitants as the number one priority.  Furthermore, we expect the more stringent 11m rule that applies in Scotland will eventually be applied throughout the UK, which we see as a positive step.  After all, a good ventilation system should improve quality of life, not endanger it.

Domus Ventilation add two new CIBSE Accredited Residential Ventilation CPD Courses

Following the release of its newly updated and revised Continuing Professional Development (CPD) CIBSE accredited course on ‘Residential Ventilation Principles and Building Regulations’ last year, Domus Ventilation has launched two further complimentary courses: ‘MVHR Design & Best Practise’ and ‘Pre Planning Conditions & Ventilation’.

‘MVHR Ventilation Design & Best Practice’ takes an in-depth look at how to design an MVHR system and best practice based on real world ‘dos and don’ts’ examples.  This detailed course covers air flow rates for different types of properties; sizing & selecting of ductwork; how to ensure the correct MVHR unit size is used and where to site it; minimising noise; and the importance of good system design for energy efficiency.  Installation & Commissioning are also addressed.  The course includes a range of MVHR system drawings to help illustrate best practice, along with common mistakes to avoid.

‘Pre Planning Conditions & Ventilation’ focusses on ventilation strategies, why they are important and how to achieve planning compliance, as well as providing the best indoor air quality for occupants.  It looks at ventilation in relation to Approved Document F (Ventilation), the new revision of Part F due this year, Part L1A, SAP Assessments, and the Domestic Building Services Compliance Guide.  Two real world case studies are covered in-depth to illustrate how ventilation system design can be adapted early on in the build process to meet planning conditions.

These two new CIBSE accredited CPD courses join the existing Domus Ventilation ‘Residential Ventilation Principles and Building Regulations’ course which looks at the importance of ventilation in the residential new build industry, and lays clear the considerable changes to Part F – Ventilation of the Building Regulations.  The aim of this course is to clearly explain why ventilation is so important, not only for the health of the occupant but also for the fabric of the building.  Topics covered include why ventilation is necessary, with an increased emphasis on pollutants and indoor air quality; the types of ventilation available, along with supporting ductwork and installation practices; and the pertinent regulations / directives.  New Mechanical Ventilation with Heat Recovery (MVHR) guidelines and best practice also features within the course.  Part B – Fire Safety is addressed for the first time in this recently revised course, looking at the changing requirements, which differ across the nations, when it comes to the use of combustible material in cavities. 

The three CIBSE accredited CPD courses have been written by the Domus Ventilation Specification team, using their breadth of experience and in-depth knowledge of the residential ventilation sector.  They have been produced specifically for Chartered Engineers, Energy Consultants, Engineering Technicians, Incorporated Engineers, Mechanical & Electrical Consultants, Mechanical Consultants, and Specifiers.

Each course runs for a maximum of one hour and can be held at a customer’s premises or online via Microsoft Teams.  To book a course, contact

For information on Domus ventilation, go to

Domus Ventilation Revit® BIM Files Now Available as Direct Download from

Domus Ventilation, manufacturer of market-leading mechanical ventilation systems that save energy and improve indoor air quality, is pleased to announce that its full range of Revit BIM (Building Information Modelling) files can now be downloaded directly from its website,, free of charge.

BIM is a government driven shared knowledge resource, providing all of the information about every component of a building, in one easy to access place.  Autodesk Revit is a BIM software for architects, structural engineers, mechanical, electrical, and plumbing engineers, designers and contractors.  It is used to create co-ordinated, consistent and complete model-based designs that drive efficiency and accuracy across the project lifecycle, from conceptual design, visualisation and analysis to fabrication and construction.  Using BIM data reduces the risk of mistakes or discrepancies at an early stage, making for more cost-effective, safe construction.

The Domus Ventilation BIM library features an extensive array of products, including energy saving, whole house Mechanical Ventilation with Heat Recovery (MVHR) appliances, as well as award winning Radial semi-rigid duct systems and its full range of rigid ducting and accessories, which incorporates Domus Thermal duct insulation and duct sound attenuators.

BIM ‘Object’ data on Domus Ventilation products includes detailed information such as product properties, geometry, visualisation data and functional data that enables the ‘object’ to be positioned and behave in the same manner as the product would in-situ.  Airflow rates, for example, can be set at each grille or air valve, allowing engineers to easily and more accurately estimate pressure losses and velocities within the ductwork, which isn’t possible using other design packages, such as AutoCAD.  Product dimensions are automatically calculated to ensure it fits into the desired design space and even the correct amount of product required is calculated within BIM to prevent product wastage.  In addition, BIM enables parts to be automatically scheduled during the design process, for speed and maximum convenience.

To access Domus Ventilation’s Revit BIM files go to  For further information please contact

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