Replace trickle vent covers

Swap old trickle vent covers for new ones on your window frame in under an hour, no drilling into walls needed.

TV-01Identify your vent type and take it apart mentally firstTrickle vents sit in a slot in the window frame, not the wall, so this job needs no drilling into brick, block or stud. Open the window and look at the vent: uPVC ones usually clip in and out, timber-frame ones are often screwed. Note the length in mm (common sizes are 300mm and 400mm) and any brand name moulded into the plastic, so you buy a matching replacement.

TV-02Buy the right replacement ventMatch the old vent's length, colour and airflow rating (shown in mm² or as a code like 5000mm² equivalent area) so the room keeps the same background ventilation. This matters most in kitchens and bathrooms, where Building Regulations Part F sets a minimum background ventilation area — do not fit a smaller or lower-rated vent than the one you're removing in these rooms.

RULES

1 each · Replacement trickle vent (external hood + internal slider, 300mm or 400mm)

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KNOW THE RULES

Building Regulations Part F sets minimum background ventilation for habitable rooms, kitchens and bathrooms. Replace like-for-like or better; don't downgrade the airflow rating.

TV-03Lay out your tools and protect the sillWork with the window open so you can reach both sides of the vent. Lay a cloth or dust sheet on the inside sill to catch old screws, clips and grime. Have a small flat screwdriver and a Phillips screwdriver ready, plus a cloth and mild detergent for cleaning.

1 each · Dust sheet or old towel

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1 each · Small flat screwdriver

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1 each · Phillips screwdriver

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TV-04Remove the external vent hoodFrom outside (or by leaning out if the window opens fully), find the small tabs or screws holding the hood on. Clip-in types release with a flat screwdriver gently pressed against the retaining tabs; screwed types just need the screws backed out. Keep the old screws in case the new vent doesn't come with its own.

TV-05Remove the internal slider or coverInside, the vent usually has a sliding louvre or a hinged flap that opens and closes the airflow. Slide it to the open position, then unclip or unscrew it from the frame the same way as the outer hood. Set both old parts aside for disposal.

TV-06Clean out the vent slotWipe out the channel in the frame with a damp cloth and mild detergent to remove dust, dead insects and old sealant crumbs. Let it dry fully before fitting the new vent, so any clips or screws grip properly.

1 bottle · Mild detergent

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1 each · Cleaning cloth

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TV-07Fit the new internal sliderClip or screw the new internal part into the cleaned slot, checking it slides or hinges smoothly between open and closed. Don't overtighten screws in uPVC — snug is enough, as overtightening can crack the plastic.

TV-08Fit the new external hoodClip or screw the outer hood into place, lining it up with the internal slider so airflow passes straight through. Check the hood sits flush against the frame with no gaps that could let rain in.

TV-09Test and weatherproofOpen and close the internal slider a few times to check it moves freely. If there's a small gap between the vent body and the frame, run a thin bead of clear silicone sealant around the outer edge only — never seal the vent slots themselves, or you'll block the airflow.

1 each · Clear silicone sealant (small tube)

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TV-10Tidy upBin the old vent parts and any offcuts of sealant. Wipe down the sill and give the window a final wipe with glass cleaner so there's no residue.

1 bottle · Glass cleaner

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