The world is now a very different place compared to 2010, the year that Building Regulations Ventilation: Approved Document F was last revised. In the intervening years, we have learnt considerably more about Indoor Air Quality (IAQ), have had to contend with a pandemic, and now have the Future Homes Standard to meet in 2025, which requires average new homes to reduce carbon emissions by 80%. Building Regulations is the method being used to achieve the Future Homes Standard.
In this context, there is no doubt that Building Regulations Part L (Conservation of fuel and power) and Part F were ripe for an update. The new versions were published in December 2021, with the immediate aim to ensure new homes built from 2022 produce 31% fewer carbon emissions compared to current standards. A further revision coming into force in 2025.
The revisions to Part F are a direct response to this requirement. So, what’s changed?
Under the previous regulations, smaller property developments were exempt from airtightness testing. However, this has now become is mandatory in all newbuild dwellings.
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 efficient 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 per the table below.
|No. of bedrooms
|Previous min. ventilation rate (l/s)
|New min. ventilation rate (l/s)
For larger properties, this increase 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.
Two key changes have been introduced with regards to background ventilation.
The first is 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 for the property as a whole.
The second change applies to extract-only systems, such as MEVs, where the background vents must now be doubled in size from 2,500mm2 to 5,000mm2. This may well impact on the property’s façade and window sizes.
Natural ventilation systems, such as background vents, remain an option, although only for less airtight homes with a design air permeability of more than five. 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.
Air pollution guidance
Thanks to air pollution now being firmly on the news agenda, as well as 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 total volatile organic compounds (TVOC).
In areas with high levels 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 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 failing 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 the rules, the reporting procedures have now 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, while householders have to be issued with a Home User Guide.
So much has changed since Building Regulations Ventilation: Approved Document F was last revised. The changes made to Part F are a reflection of this but, more importantly, look to the future at how we, as an industry, can help meet net-zero targets and provide housing fit for purpose.
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