EPISODE: 022 - APPROVED DOCUMENT F - VENTILATION VOLUME 1 AND VOLUME 2
- Piotr Bytnar BEng (Hons) MSc CEng MIStructE
- Nov 5, 2024
- 18 min read
Updated: 10 hours ago
BYTNAR - TALKS
EPISODE 022 - APPROVED DOCUMENT F - VENTILATION VOLUME 1 AND VOLUME 2
This episode is for people who want to know more about Approved Document Part F – Ventilation Volume 1 and Volume 2
You should like this episode if you ask yourself questions like:
What are the ventilation requirements for dwellings and non-dwelling buildings according to Approved Document F?
How should mechanical ventilation systems be commissioned to meet building regulations?
What are the exemptions from ventilation requirements in Approved Document F, and which types of buildings are excluded?
What is the difference between Volume 1 and Volume 2 in Approved Document F?
How do you ensure adequate extraction and supply of fresh air in a building while preventing the infiltration of external pollutants?
What is purge ventilation, and how can it be achieved using natural or mechanical methods?
How does upgrading the building envelope affect natural ventilation, and what holistic approaches should be considered?
What are the testing and commissioning standards for ventilation systems in new or renovated buildings?
What are the special ventilation considerations for car parks, offices, and large congregation spaces?
This is Bytnar Talks: The Engineer Takes on Construction – Episode 22
Hi, I'm Piotr Bytnar. Each day, I help my clients plan and design building projects through Bytnar Limited – a consulting Chartered Structural Engineers practice. My biggest passion, and the cornerstone on which I've built my business, is finding clever solutions for construction projects.
I am a Chartered Structural Engineer and a budding software developer, so you can rest assured that I will strive to talk about the best practices and the use of new technologies in the industry. And if you're embarking on a construction project, or are involved in planning, designing, and building the world around us, you'll find this podcast useful.
Approved Document F: Ventilation – Volume 1 and Volume 2
Hi, and welcome to Bytnar Talks, your favorite podcast on all matters of architecture, engineering, and construction. It is Friday, the 28th of June 2024, and I am here back with you with the 22nd episode and information on Approved Document F: Ventilation, Volume 1 and Volume 2.
Before we dive deep into this week's episode, let us recap the last episode for reference. Last week, I talked about the Approved Document D and E – toxic substances and resistance to sound.
To recap quickly:
Requirement D1 is all about cavity insulation and the potential of insulation polluting the indoor air by off-gassing of Urea Formaldehyde.
Approved Document E – Resistance to the Passage of Sound – comes with four requirements and Regulation 4:
Requirement E1 deals with sound from other parts of the building and adjoining buildings. It basically sets that the design must provide reasonable resistance to sound from adjacent parts of the building and adjoining buildings.
Requirement E2 deals with sound within a dwelling house. It says internal walls and floors must resist sound transmission, particularly between bedrooms and living rooms.
Requirement E3 deals with reverberation – oh, that's a horrible one – reverberation in common internal parts. We need to prevent excessive reverberation in common areas like corridors and stairwells in residential buildings.
Requirement E4 then goes on to deal with acoustic conditions in schools. Well, it actually does not really, as it refers us to follow standards set by the Education Act 1996 and the Department for Education.
Regulation 41 deals with sound insulation testing. It tells us that sound performance testing is required for new buildings and certain material changes, with results submitted to Building Control. Some exemptions apply if using Robust Details – pre-approved methods.
In this episode, I will move to the Approved Document F and the considerations for ventilation in dwellings and buildings other than dwellings. So without further ado, let's dive into the text of the Approved Document.
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In this episode, I will talk about the statutory guidance contained within the Approved Document F – Ventilation. The episode will follow its standard format for the material talking about the Approved Documents. I will first read you the text of the actual regulation, and then we go section by section, giving you a little bit of a commentary, or including auxiliary information where appropriate.
Well, knowing me, it may be inappropriate information from time to time – but don't worry, most of it is good information anyway.
The document consists of two volumes:
Volume One deals with dwellings
Volume Two with buildings other than dwellings
Both volumes deal with the requirements through five sections: Section 0 to 4, and reference Regulations 39, 42, and 44.
Volume One adds Regulation 42.
Regulation 39 puts an obligation on the provision of information regarding the ventilation system and its maintenance.
Regulation 42 puts an obligation on testing of the mechanical ventilation efficiency in new dwellings – so-called airflow rate testing.
Regulation 44 puts an obligation on notification of commissioning of the mechanical ventilation system to the appropriate Building Control Authority – unless the work carried out cannot be tested.
All right, we've got the flavor of the topic now, so let's get into the nitty-gritty of the Approved Document.
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So, starting with the text of the legislation:
Part F – Ventilation: Means of Ventilation
Requirement F1(1): There shall be adequate means of ventilation provided for people in the building.
Requirement F1(2): Fixed systems for mechanical ventilation and any associated controls must be commissioned by testing and adjusting, as necessary, to ensure that the objective referred to in sub-paragraph (1) is met. Requirement F1 does not apply to building or space within a building:
A) into which people do not normally go,
B) which is used solely for storage, or
C) which is a garage used solely in connection with a single dwelling.
So, simple reading—that is followed by a wide interpretation, as usual. In the gist the air within the dwelling needs to be refreshed and cleaned of vapour and pollutants. Internally generated vapour and pollutants need to be removed, and the exterior pollutant infiltration minimized.
This generally means the provision of trickle ventilation, mechanical ventilation in the rooms where vapour and pollutants are released, and purge ventilation throughout.
Starting with Section 0, which eases us into the document, its structure, and understanding, we are straight up being told that Volume One is for dwellings, and that dwellings means self-contained units—no sharing toilets or kitchen with anyone.
There are a number of circumstances where Requirement F does not apply, including:
Schedule 2 buildings
Crown buildings
Statutory undertakers
Airports
Certain small additions
Police and some small building extensions
There are, naturally, expectation rules—some certain rules and limits applicable to all these cases, as may be the case with historical buildings too.
Note that emergency repair work does not need to be notified prior to work taking place, and some minor works do not require notification also. But in any case, the requirement needs to be met.
As ever, the interpretation of the requirement contained within this document may interact with other requirements, and in such cases, the higher expectation guidance should be followed.
Section 1 informs us of the required ventilation rates in the situation of reasonable external air quality. It is important to provide the right level of ventilation, but equally so to maintain a habitable level of noise within the dwellings.
And this point concerns the ventilation units themselves, the ducting, but also the noise outside. The levels should be low:
30 dB for noise-sensitive rooms
45 dB for less noise-sensitive rooms
Measured to BS EN 8233 standard, or BS EN 13141 in case of MVHR (Mechanical Ventilation with Heat Recovery) systems.
There is no point in having a system that cannot be maintained, but the requirements state that they need to provide sufficient access for maintenance—so we are safe and sound on this occasion, aren’t we?
Typically, the ventilation will be provided by targeted extraction of the air from kitchens, bathrooms, and utility rooms—or any other room where elevated levels of pollutants or water vapour can be present. Whole dwelling ventilation and purge ventilation need to be provided as and when needed.
All types can be provided by natural means, using stack effects, mechanical means, or a mixture of both. Departures from the guidance can be made, just as long as the performance is justified.
The performance criteria of pollutant and moisture concentration are given in Appendix B of the document. But the guidance goes as far as prescribing the performance forms of ventilation systems, which correlate with the achievable air quality standards.
Background ventilators:The standard references equivalent area in mm² and requires conspicuous marking of the figure on the ventilator itself for verification purposes.
Extract ventilation is required in all typical circumstances, like kitchens, bathrooms, utility rooms, and sanitary accommodation. The performance is given in litres per second, and there are different figures for continuous systems and those for intermittent systems. These should generally be fitted at the highest point, but not lower than 400 mm below the ceiling.
This does not include cooker hoods, which should be generally installed to manufacturer specifications—or between 60 to 75 cm over the hob surface.
The requirements for ventilation of kitchens are:
Either 60 L/s if there is no cooker hood or a recirculation filter hood used in the kitchen
Or, if extracted to the outside, then 30 L/s capacity extractor is needed
30 L/s also applies for continuous ventilation in such cases
Utility rooms should either go by:
30 L/s (intermittent) or
8 L/s (continuous)
Bathrooms:
15 L/s (intermittent) or
8 L/s (continuous)
Sanitary accommodation:
One figure of 6 L/s, or
Purge ventilation otherwise
The dwelling should be supplied with air by either supply fans or background ventilators at the minimum of:
0.3 L/s per m² of internal floor area
or
A minimum rate based on the number of rooms, starting at:
30 L/s for studio apartments
Up to 43 L/s for a five-bedroom unit
Plus 6 L/s for every additional room
So, calculate either by m² or by prescription of bedrooms—whichever is greater. That’s the requirement for air ventilation.
To allow for the air circulation, doors should be undercut by a minimum of 10 mm when there are finishes on the floor. When there's no finish on the floor, it should be 20 mm to allow for the finishing to be put in at a later date.
Purge ventilation is required for all habitable rooms, allowing for four air changes per hour, but it may need to be greater. The window or door opening needs to be at least 1/20th of the floor area if openable to 30% or more, and below that range of opening, it needs to be at least 1/10th of the floor area.
Naturally, a mechanical option is always on hand if we need it. We are directed by the guidance to BS EN 13141 for determination of performance of the components of the system we intend to use.
The requirement assumes the background ventilation remains open, and that we can control the ventilation either manually or automatically. The background ventilation is to be placed at least 1.7 m above the floor level to reduce cold drafts—but not too high to inhibit manual operation.
Basements may require additional consideration, depending on whether they are connected to the house and allow continuity of ventilation or not, as well as depending on the number of exposed facades of that basement. In any case, the basement may be treated as a single dwelling above ground, with a consideration for ventilation of at least one room—even if there are no habitable rooms in that basement whatsoever. Mechanical ventilation may be required.
Ventilation of inner rooms can be done through another room via a permanent opening between the rooms of at least 1/12th of the combined area of the rooms, provided that purge ventilation is possible in the access room, or the room is serviced by 10,000 mm² of equivalent background ventilation.
Depending on the system of ventilation we choose for our dwelling, the requirement will follow different levels of performance. For less airtight dwellings, we can follow requirements for natural ventilation. For all dwellings, we may use either:
Continuous mechanical extract ventilation, including natural background ventilation, or
Mechanical ventilation with heat recovery (MVHR)—that means no natural background ventilation.
What is a less airtight dwelling, you ask? It is a dwelling that leaks air at more than 5 m³/hour/m² at 50 Pascals of pressure as designed, or 3 m³/hour/m² as built.
For highly airtight dwellings, mechanical ventilation may be the only solution.
Depending on the ventilation approach you take, there are different minimum ventilation limits prescribed by the guidance. Certain situations may require Bespoke (BPO) specifications and specialist input.
It goes without saying that the installation needs to be done to appropriate standards and commissioned in accordance with an approved procedure. You will find a completion checklist and commissioning sheet within Appendix C of this Approved Document. This information should be completed by the installer.
Section 2 now deals with ingress of external pollutants, which needs to be kept to a minimum—while at least within the boundaries of the Air Quality Standards Regulations 2010.
The sources of pollution will vary, from:
being next to the street,
close to exhausts of combustion from other dwellings,
construction sites,
or any other such example.
A table showing typical pollutants, exposure limits, and exposure time is included within the guidance.
For the best solution, we need to consider:
the location of the building,
type of pollutant,
inlets and outlets positions,
prevailing winds, and so on.
The provision of mechanical and filtered solutions may be the ultimate answer in the worst-case scenario, but no specific mention of such is given within the guidance.
When it comes to relative humidity, we talk about the measurements taken during colder months. The limit for a new dwelling house is:
65% relative humidity at 1-month average,
75% at 1-week average,
and 85% at 1-day average.
For existing buildings, measurements at the internal plaster (pH) of the external wall should show the surface water activity levels at the same time intervals as:
0.75,
0.85,
or 0.95, respectively.
This parameter allows determination of the condition for mould growth in the wall by checking if the material is rather drying, or rather getting more moisture—which mould needs to grow.
Section 3 refers to work on existing dwellings, which should not change the building for worse, but try to improve the quality wherever and whenever possible. So, for change of use, we look into upgrading to the standard as well, when we create new rooms. We ought to be in line with the standard.
Now, making changes or otherwise improving on the envelope of the building may inadvertently bring the ventilation level of the building below the standard required. Remember—we need to get rid of bad air, but bring some good air in. And any improvement very often seals the envelope, inhibiting that access—that trickle of air—to within.
Guidance comes to aid with simple methods to assess the impact of improvement, and gives us a checklist in Appendix D for the identification of possible requirements for bringing the property in line with the regulations. The checklist will likely go over and above the expectations of the regulation, but it's very handy, and a starting point to consider.
Replacement of windows should ensure sufficient background ventilation, at least matching the one in existing windows—but preferably, that of the guidance, or as close to the requirement as possible.
Addition of rooms, bathrooms, wet rooms will have standard repercussions, requiring the provision of enough ventilation, but refurbishment to these rooms will not automatically trigger such requirements. And if we are using the existing cabling, we will not need to inform Building Control of the work.
Section 4 goes on to talk about the Requirement F1.2, and the Regulations 39, 42, and 44. The system needs commissioning, testing, and recording according to standard procedures. That’s it—end of story.
Although, the document goes on to describe the inspection standards for:
background ventilators
intermittent extract ventilation
ducted systems
airflow rate tests of all extract fans
cooker hoods
continuous extract and supply fans
and all terminals and controls of the systems too
The commissioning should end up with the preparation of operating and maintenance instructions, transferred to the building owner together with the complete commissioning.
The manual suggests cleaning and maintenance intervals, and all the auxiliary information that can assist in the operation and maintenance of the system. Some of the information should end up in the Home User Guide for new dwellings—treating on the system in layman’s terms.
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Now off to Volume Two, and consideration for ventilation in buildings other than dwellings.
Section 0 of the document and the text of the legislation remain the same for both volumes, so I will head straight to the Interpretation ("In the G") section of the episode, and follow Sections 1 to 4, with a sneak peek into appendices.
In the G’s, the Secretary of State considers the requirement fulfilled where:
the high water vapour or polluting rooms are well ventilated,
occupants of the building can enjoy minimum levels of outdoor air supply,
and are given an option for purge ventilation of occupied rooms and sanitary accommodation.
Some occupiable rooms may need air quality monitoring. The entry of external pollutants should be minimized, and as as ever, the system should be serviceable and maintainable—not too noisy, nor allow for drafts, ingress of rain, or be risky to health.
Section 1 lays down the provisions for ventilation in different types of buildings—be it specific types of occupiable rooms, offices, car parks, and others.
(Not offices and car parks—it’s all about the pesky miasma that can come about from too much vapour or pollutants, which can be wide on the spectrum—from stinky socks through flu, to carbon monoxide.)
The ventilation system should be designed and installed properly:
to avoid noisy scenarios,
and to allow due maintenance and service.
Ventilation generally follows the principles of:
extraction,
supply of fresh air,
purge ventilation, and
monitoring of indoor air quality.
The requirement can be achieved by means of natural or mechanical ventilation, but should we choose to go the natural route, the guidance refers us to the Chartered Institution of Building Services Engineers (CIBSE):
Applications Manual 10, and
Manual 13.
The consideration of performance level of the system is stated in Appendix B, and includes considerations of bio-effluence, as well as measurement of exposure limits for:
Carbon Monoxide (CO),
Nitrogen Dioxide (NO₂),
Formaldehyde,
Total Volatile Organic Compounds (TVOCs), and
Ozone.
We are also guided to use CO₂ monitors to verify the efficiency of ventilation in the given room. Naturally, the approach will vary from room to room and may not always give the right reading. But for offices, and where people breathe a lot, being under 400 parts per million (ppm) is considered a well-ventilated space, and readings over 1500 ppm will require improvement.
Again here, the installation of the system needs to be good and needs to pass the commissioning stage.
The rooms that will need monitoring of their air quality will be:
offices
walk-in fridges
assembly rooms
restaurants
concert halls
…and on and on—basically, wherever people spend their time and/or congregate—those are the rooms where monitoring will be needed.
The preferable method of monitoring is by non-dispersive infrared (NDIR) CO₂ monitors, but there are exceptions.
Rooms that are small or large:
A small room is considered one with a volume of 125 m³ or 50 m² of floor area.
A large room is considered to be over 800 m³ in volume or 320 m² of floor area.
These do not fall under the requirement of monitoring.
Extract ventilation in offices should be provided in typical places of heightened pollution:
sanitary accommodation
bathrooms
washrooms
food and beverage preparation areas
and printer rooms
Printer rooms should be created for heavy use of printers, which means at least 30 minutes per hour of use, and serviced with extraction of 20 litres of air per second per machine, while still ensuring the whole building ventilation rate is met.
Sanitary accommodation and bathrooms should have intermittent air extraction at the following limits:
15 L/s per shower or bath
6 L/s per WC pan or urinal
However, the sanitary accommodation extraction should have an option to work continuously.
Rules for remote kitchens are similar to those of domestic kitchens, with a 15 L/s requirement if microwave and kettle are in use only.
Rooms without openable windows should have extraction working at the time of use and for a minimum of 15 minutes thereafter.
Naturally, specialist buildings and commercial kitchens will follow their own requirements.
The requirement of “as high as possible but not lower than 400 mm from the ceiling” for ventilators in naturally ventilated premises is also applicable here, but passive stack ventilation terminals should be located in the ceiling.
Air supply for offices should be at least:
10 L/s per person,
or
1 L/s per m² of floor area.
Common areas in the office will need 0.5 L/s per m² of the common area.
All natural ventilation should involve openings of at least 2% of the floor area.
In more complicated scenarios, or in cases of higher levels of pollutants, the document refers us to CIBSE Guide A – Environmental Design.
Purge ventilation is a must for all offices, and ventilation should be controlled either manually or automatically.
The system generally should not recirculate air into other rooms, unless it does so through:
UVC germicidal irradiation systems,
or HEPA filters.
When it comes to car parks, the onus is to limit carbon monoxide concentration to maximum levels of:
30 parts per meter in an 8-hour period,
or 90 parts per meter in a 15-minute period—especially at ramps and exits.
For naturally ventilated car parks:
Each level needs to have an equivalent area opening of 5% of the total floor area at that level,
with the opposite side receiving at least 1.25% of area each.
For car parks with mechanical ventilation:
The opening can be reduced to 2.5%,
with ventilation capable of delivering 3 air changes per hour,
with a caveat for exits and ramps where cars can queue,
where the performance should be increased to 10 air changes per hour.
Other ventilation will need to be capable of:
6 air changes per hour in general,
and 10 air changes at the position of car queuing.
It would be unnatural for the guidance not to refer us for further information to CIBSE, HSE, AA, and ASHRAE guidances.
For other buildings, we are generally referred to CIBSE Guide A, and to a two-page long table describing:
type of the room,
expected performance of the ventilation system,
or reference to further guidance.
You know—things like:
for prisons, go with the Ministry of Justice publication PSI 17-2012: Certified Prisoner Accommodation
or for schools and education, refer to the Education (School Premises) Regulations 1999, among others.
Section 2: Minimising the ingress of exterior pollutants is verbatim to that of dwellings, so I will not go through this here again.
Section Three: Work on Existing Buildings—follows the logic of the dwellings, but without consideration of typical dwelling-like buildings and additions of habitable rooms or conservatories.
Section Four is also similar, but without Regulation 42, and regards commissioning and providing information. The commissioning process is required to be according to CIBSE Commissioning Code M, with additional guidance from BESA for ductwork, and forms part of the energy consumption assessment for Part L requirements, and must be done together on one form.
The information about the system should be provided in the building logbook, and a copy of the commissioning sheet handed over to the building owner.
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So this is it, folks—Approved Document F: Ventilation, Volume 1 and 2. Let’s sum it up:
🔹 General Overview:
Buildings must have adequate means of ventilation for occupants.
Mechanical ventilation systems must be commissioned to ensure they meet the required objectives.
Exemptions include:
Spaces where people do not normally go,
Buildings used solely for storage,
And garages for single dwellings.
🔹 Volume One – Dwellings:
Goes on for five sections.
Section 0:
Applies to self-contained dwellings, meaning units with no shared kitchens or bathrooms.
Certain buildings, including historical structures and small extensions, can have specific exemptions or additional considerations.
Emergency repair work and minor works may not need prior notification—but must still meet requirements.
Section 1:
Deals with ventilation provisions:
Ensure adequate ventilation while maintaining low noise levels:
30 dB for sensitive rooms,
45 dB for other rooms.
Extra ventilation is generally required in:
Kitchens, bathrooms, utility rooms, and sanitary accommodations.
Minimum ventilation rates are specified per room type.
Purge ventilation should enable four air changes per hour, with specific window/door opening sizes.
Both mechanical and natural ventilation methods are addressed, with different requirements depending on the building's airtightness.
Section 2:
Focuses on external pollutants:
Minimize ingress within boundaries of the Air Quality Standards Regulations 2010.
Consider location, pollutant type, inlets/outlets, prevailing winds, and more.
Relative humidity limits are set to control mould growth.
Section 3:
Existing dwellings:
Any changes should improve ventilation quality wherever possible.
Guidance includes assessing the impact of improvements and using the checklist for compliance.
Replacement windows should maintain or improve current background ventilation levels.
Section 4:
Commissioning and Information:
System must be commissioned and tested to standard procedures, with results recorded.
Inspection standards are outlined for various components.
🔹 Volume Two – Buildings Other Than Dwellings:
Section 0:
Describes what the Secretary of State considers acceptable to fulfill the requirements.
If rooms with high moisture or pollutants are well ventilated, occupants have adequate outdoor air supply, and purge ventilation is available—that’s good enough.
The system must also be:
Maintainable,
Not too noisy,
And should avoid draughts or rain ingress.
Section 1:
Similar to Volume One but applies to various building types:
Includes offices and car parks, which have tailored requirements.
Ventilation must avoid mould and pollutants, be properly designed, and allow maintenance.
Extract, supply, purge ventilation, and indoor air quality monitoring are required for key spaces.
Section 2:
External pollutants:
Mirrors that of dwellings—focusing on minimizing the ingress of pollutants.
Section 3:
Existing buildings:
Similar to dwellings, but without reference to home-specific additions like habitable roofs or conservatories.
Section 4:
Commissioning and provision of information:
Same structure as dwellings, but uses a different commissioning standard.
Commissioning should follow CIBSE standards and be part of Part L energy assessment.
System information should be included in the building logbook and handed over to the owner.
In the next episode, we will move on to Approved Document G – Sanitation, Hot Water Safety, and Water Efficiency.
🎵 [Music] 🎵
I hope you enjoyed this episode and that the considerations of Approved Document F: Ventilation are more friendly to you now.
If you have any questions, reach out to me on LinkedIn or send me an email—I'm more than happy to help you out.
At Bytnar, we deal with planning, designing, and managing your projects, and we are always glad to facilitate a free initial consultation to steer you in the right direction.
Visit www.bytnar.co.uk and reach out to us—whether your question is “Can you help me with my project?” or “What should I do?”—we will be able to give you a piece of non-obligatory advice.
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See you next week!
Remember: Bytnar Designs the World Around You.
Toodloo! 🎤

Piotr Bytnar BEng (Hons) MSc CEng MIStructE
Chartered Structural Engineer who deals with the Architecture of buildings. His Master's Studies led him to an in-depth understanding of risk and contract arrangements in construction as well as specialist knowledge in soil mechanics.
He and his team help homeowners and property developers to design and deliver construction projects reducing waste in time and the cost. He believes that the construction project is an iterative process that can be well managed and it is best managed if all the aspects of the project definition and management are dealt with in-house or coordinated by one organisation. His team works to all stages of RIBA and ISTRUCTE stages of work and enables contractors to deliver projects on-site providing risk evaluations, methodologies for execution of works and temporary works designs.
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