Approved Document F - Do I Need To Fit Trickle Vents? 

Dear FENSA Approved Installer,

The changes to Approved Document F were published on the 15th December 2021.

The changes, which require the majority of replacement windows and doors to be fitted with trickle vents, contradict regulations which will come into force at the same time that require such products to be more energy efficient.

Despite numerous meetings with the relevant government departments, where we have highlighted the negative impact this will have on people’s homes, they have informed us the changes will proceed as planned and come into effect on the 15th June 2022.
We would recommend you read the Approved Document in full to make sure that you understand all of the changes and requirements. Approved Document F: Volume 1 applies to dwellings (
Please note that these changes are for England ONLY. There are no current changes to the Building Regulations in Wales. When there are, we will keep you updated.

What Do You Need To Consider On Trickle Vents?

It will be up to every FENSA Approved Installer installation company to comply with the Approved Document and the following questions should be considered at every sale and/or survey:

Does The Property Already Have Trickle Vents?

  • Yes – The replacement windows and doors must also have trickle vents (or another method of background ventilation), and the size of these vents must not be smaller than those installed in the previous windows.
  • No – go to the next question

Are You Replacing Less Than Or Equal To 30% Of The Windows & Doors In The Property?

  • Yes – No trickle vents are required provided that no more than one other minor energy efficiency measure has been completed at the property such as cavity wall insulation. 
  • No – Go to the next question
Please note that windows installed post June 2002 are an energy efficient measure in the same way as cavity wall, draft proofing, loft insulation top up or external wall insulation. 

Is There A Mechanical Ventilation With Heat Recovery System Installed At The Building Or Any Other Ventilation Provisions That Can Be Demonstrated To A Building Control Body That They Comply With The Requirements Of Paragraph 3.2?

  • Yes -  No trickle vents required
  • No –  Go to next question
Paragraph 3.2 reads as follows;

When other building work is carried out that will affect the ventilation of the existing dwelling, for example:

a. replacing a window or door
b. doing energy efficient work

the ventilation of the dwelling should either:

a. meet the standards in the relevant approved document
b. not be less satisfactory than before the work was carried out

NOTE: Ventilation through infiltration should be considered to be part of the ventilation provision of a dwelling. Reducing infiltration might reduce the indoor air quality of the dwelling below the standards given in Appendix B.

Does The Property Have Continuous Mechanical Extract Ventilation (a ducted system where a single fan draws air continuously from each room constantly or individual room extract fans)?

  • Yes – No trickle vents required in wet rooms (kitchen, utility, bathroom, WC), but you must fit 4000mm² Equivalent Area in all other rooms.
  • No – Go to next question

Are There Any Other Ventilation Provisions That Can Be Proven Will Not Make The Previous Air Infiltration Of The Property Worse?

  • Yes – Record these provisions and save to the work file, they will be required to be assessed at time of inspection of this property.
  • No – Fit trickle vents

Can You Feasibly Adopt The Minimum Equivalent Vent Sizes Set Out In Table 1 In Each Window?

  • Yes – Install the vents as per the table below 
  • No – Install vents as close in size to the table below as possible


Room Minimum equivalent area of background ventilators Minimum equivalent area of background ventilators when the property has continuous mechanical ventilation
Habitable Rooms 8000mm² 4000mm²
Kitchen 8000mm² Should not be installed
Bathroom with or without a WC 4000mm² Should not be installed
Utility Room No Minimum Should not be installed

New Training Course

The FENSA Academy will be running an updated course on Building Regulations, including the new requirements, from the 30th March. This will be a 1 hour online course at a discounted cost to FENSA Approved Installers of £35 + VAT per person. 

To book on the course for this date or on the 12th April, 28th April or 20th May please either book directly here or email with your Name, FENSA ID and contact phone number and a member of the team will be in touch shortly.

The above information we will put into a guidance document for all FENSA Approved Installers that will be available to download from the FENSA Installer Portal. We will also make the above questions available on a page on the FENSA website for the FENSA community to refer to when speaking to potential customers about replacing their windows and doors.
Please keep an eye out for future emails on the changes being made to the Building Regulations over the coming months. We will ensure you’re ready to go for the 15th June.

All the best,

Lis Clarke,
Operations Director

Have a question about your FENSA account or membership? Contact our Installer Team at
Need technical help? Email our Technical Team direct at
Resources for your business:
Practical safety precautions when installing windows & doors during the COVID-19 pandemic (PDF)
Guidance on completing a risk assessment (PDF)
Risk assessment template (DOC)
Resources for your customers:
Homeowner guide to having windows & doors installed during COVID-19 (PDF)
What to ask your window fitter
Condensation on the outside of a window - explained (PDF)
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