Installers – Do You Need to Install Trickle Vents?


The long-awaited revisions to Building Regulations have arrived and there are a number of updated regulations that are going to have a direct impact on the fenestration industry.

The changes to Approved Document F – Background Ventilation require the majority of replacement windows and doors to be fitted with trickle vents. 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 (

Why are trickle vents important? 

All buildings must include ventilation to ensure the health and well-being of everyone inside. Rapid ventilation can be achieved by opening a window but trickle vents play an integral part in providing constant, background ventilation.

Using trickle vents in every room to provide background ventilation is never a bad thing. However, there are rooms in a home where they are of particular use. These are areas such as kitchens, bathrooms, utility rooms etc, where appliances, showers and baths produce large amounts of moist, damp air which needs to be expelled from the room.

When a window is not well ventilated this can result in a build-up of condensation, which when left can lead to an increase in potentially harmful mould spores.

What Do You Need To Consider On Trickle Vents?

It will be up to every installer to comply with the Approved Document and the following questions should be considered at every sale and/or survey. FENSA have issued the following checklist:

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

When are the changes coming into effect? 

These changes to Approved Documents F come into effect from the 15th June 2022. It is important to note that the date on which the contract was signed by the customer has no bearing on the registration of the work with FENSA. If the installation takes place from the 15th June 2022 onwards it will be expected to comply with the new building regulations. 

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Have a questions about trickle vents? Contact us.

If you have any questions about trickle vents or any aspect of windows and doors please contact us and we can help.

Tradeglaze are specialists in double glazing, working directly with installers, commercial clients and with new build project managers throughout the Lincolnshire region.

We have been operational within the double glazing industry for more than 25 years, supplying direct to the trade and manufacturing in-house for a significant portion of that. We are FENSA registered, local, reliable and trusted, and have an outstanding rating from our customers. You can read what our customers say about us here.

For a free, no-obligation estimate simply start your online quote below or you can call us on 01522 539578 and one of our friendly advisors will be happy to help you with your options. While our showroom is currently closed, our team of specialists are available to ready to help you, wherever in your home improvement journey you are.

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