FAQ – What are trickle vents and are they necessary?

A trickle vent is a small opening at the top of a window or door to allow for secure ventilation.

All new builds since the early 1990’s require passive ventilation and the easiest and simplest form of achieving this is by using trickle vents in windows and doors.

The requirements were introduced due to increased performance in glazed units. It is important that properties have controlled ventilation for good indoor air quality. For health and well-being and to protect the fabric of the building from the harmful effects of moisture and mould.

There is a common misconception that trickle vents are required in all new openings for windows and doors but this is not technically true. If you have trickle vents in your existing windows or shown on your new plans then you will need to cater for a form of background/passive ventilation.

Trickle vents can affect the acoustic performance of high performance windows allowing airborne sound to travel through the frame. If you are looking for low u-values and thermal performance it is worthwhile investigating other solutions; one of which is a Positive Input Ventilation system, or PIV system.

If your project is a new build (extension, alteration or complete new building)

It is important that you consult with your Building Control Inspector to make sure that your requirements have been fully specified within your window and door quote. The total requirement for ventilation being based on floor area, number of bedrooms and the air permeability of the building.

Replacement of existing windows

FENSA certified installers like Aspect Windows will adhere to the requirements of the Building Regulations for replacement windows and the FENSA governing body. We will therefore assess the existing ventilation and if deemed inadequate suggest options to improve.

If the windows being replaced contain a trickle ventilator, the new window must also contain a trickle ventilator to the same level of performance as a minimum.

If the outgoing window does not have a trickle vent, it is not mandatory to provide a trickle ventilator. FENSA however, recommend that owing to the health benefits of trickle ventilators, they are offered to customers.

In some circumstances where security is not compromised (e.g. 1st floor and above) two stage locking (espagnolette) locks on casement windows are an acceptable form of background ventilation.

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