Do I need trickle vents?

In most homes with extract fans or natural ventilation, yes: background ventilators let replacement air in so fans can work. The exception is whole-home MVHR, where trickle vents should not be installed.

What do trickle vents do?

They let a small, controlled amount of outside air into habitable rooms so moisture and stale air can be replaced.

What does Part F say for replacement windows?

Replacement windows in England should keep background ventilators at least as large as the old ones; where there were none and no ducted system, guidance gives 8,000 mm² for habitable rooms and kitchens and 4,000 mm² for bathrooms.

Do I need them with continuous extract?

Yes. With MEV or dMEV, habitable rooms still need background ventilators so replacement air can enter.

And with MVHR?

No. MVHR supplies its own fresh air and trickle vents should not be installed.

Can I just keep them closed?

Closed vents defeat the purpose, and condensation often follows. Keep them open, especially in bedrooms.

Sources

• BEAMA guidance on Part F for dwellings in England

Related services

Extractor fan installation

Bathroom, kitchen and utility fans sized to the Part F rates, ducted outside and tested.

From £175 inc VAT per fan

Ventilation for new builds, extensions and lofts

Part F designs, MVHR or extract installs and the commissioning paperwork building control needs.

From £4,950 inc VAT per home