2021 Update to Part F Building Regulations – Approved Document F: Ventilation

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The 2021 update to the Part F Building Regulations is due to take effect from 15th June 2022.

Approved Document F covers the requirements for ventilation in both dwellings and buildings other than dwellings, this is split into two separate volumes and we have linked to the official versions of the Approved Documents on the Government website below:

Part F of the Building Regulations is very closely linked with Part L (conservation of fuel and power) as both are being improved to meet the Governments Future Homes Standard.

One way of improving energy efficiency is to reduce the heat loss through air permeability, this means building more air tight homes. However, an increased air tightness leads to reduced ventilation and therefore Part F has been updated to ensure that sufficient levels of ventilation are still provided.

Changes Under the New 2021 Part F Approved Document

Here we wanted to highlight some key differences and similarities between the current 2013 Part F Approved Documents and the new 2021 Part F Approved Documents.

Intermittent Extract Rates

The required extract rates for intermittent extract systems will remain the same under the 2021 Part F Approved Document. Kitchens will still require 30 l/s extract if adjacent to the hob or 60 l/s if located elsewhere. Utility rooms will still requires 30 l/s, bathrooms will still require 15 l/s, and Toilets will still require 6 l/s.

Continuous Extract Rates

The required continuous extract minimum high rates also remain the same under the 2021 Part F Approved Document. Kitchens will require 13 l/s, Utility Rooms and Bathrooms 8 l/s, and Toilets will require 6 l/s. The sum of all extract ventilation also known as the minimum low rate should also at least meet the required whole dwelling ventilation rate.

Whole Dwelling Ventilation Rate

Although both the current and new Part F Documents ask you to meet the whole dwelling ventilation rates, these are actually now different.

The table below shows the whole dwelling ventilation rate required under the current 2013 Part F Approved Document.

The next table shows the new whole dwelling ventilation rate required under the new 2021 Part F Approved Document.

As you can see there is now a much higher minimum whole dwelling ventilation rate required under the new 2021 Part F Approved Document, therefore the air quality in new homes going forward is going to be significantly improved.

Background Ventilators

Under the new 2021 Part F Approved Document the use of intermittent extract fans and natural ventilation through background ventilators is only recommended for less airtight dwellings. These are dwellings that will aim to have a design air permeability of greater than 5 m3/(h.m2).

Due to the new Part L Building Regulations, having such a high design air permeability will make achieving the carbon reduction targets extremely difficult and therefore it is expected that all newly design dwellings will be classified as Highly airtight dwellings with an air permeability of less than 5 m3/(h.m2).

Nevertheless, if a dwelling is classified as less air tight the minimum equivalent area of background ventilators required has been changed in the new 2021 Part F Approved Document.

Under the current Part F document there was a minimum ventilator area required for the whole dwelling depending on its total floor area and number of bedrooms.

Whereas, under the new 2021 Part F Approved Document the minimum required area for background ventilators is now taken over a room by room basis.

For continuous mechanical extract systems the current Part F requires a minimum equivalent area of 2500mm2 to be fitted in each habitable room, except wet rooms. Under the new 2021 Part F Approved Document this has been increased to 4000mm2.

Purge Ventilation

The requirement for purge ventilation remains pretty much the same between the two documents.

A purge ventilation rate of at least 4 air changes per hour directly to outside is still required. This can be achieved by opening hinged or pivot windows with an opening angle of 15 to 30 degrees having a minimum total open area of at least one tenth of the room floor area.

If the opening angle is greater than 30 degrees then the  minimum total open area can be one twentieth of the room floor area.

The Purge ventilation rates can also be met through mechanical means if required. Also, although 4 air changes per hour is the minimum required rate, higher ventilation rates may be required to meet the new overheating requirements of Part O of the Building Regulations.

To determine this we can carry out calculations such as a CIBSE TM59 overheating assessment.

Buildings Other Than Dwellings

The ventilation requirements for offices under the new 2021 Part F Approved Document also remain largely unchanged.

Toilets still require 6 l/s extract per WC/urinal, showers or baths still require 15 l/s extract, and kitchen areas still require 15 l/s where there is only a microwave present to 30 or 60 l/s where a cooker is present and the fan is located adjacent to it or not.

On the supply ventilation side there is still a required fresh air supply rate of 10 l/s per person. However, added under the new regulations is also a requirement to provide at least 1 l/s per m2 of floor area, whichever is the higher rate should be provided.

Common areas such as corridors or lift lobbies etc. also require either natural ventilation openings equal to at least one fiftieth of the floor area, or if provided by mechanical ventilation provide at least 0.5 l/s per m2 of floor area.

Summary

There a few other small changes between the current 2013 Part F Approved Documents and the new 2021 Part F Approved Documents that may be worth reading up on but we wanted to just highlight the main ones within this article for easy reference.

The new Part F Regulations take effect from 15th June 2022 so any development applying for planning permission after this time will be required to meet the latest guidance.

If you require a ventilation design under either the current 2013 Part F Approved Document or the new 2021 Part F Approved Document please contact us using our details below.

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