Should Trickle Vents Be Open or Closed in Winter?

Should trickle vents be open or closed in winter?

The answer is open, in almost every home.

Trickle vents are designed to stay open all year round, and winter is when they matter most. They can be closed for short spells in a storm or a bitter wind, but should be opened again once the bad weather has passed.

It's an easy one to get wrong. When the heating goes on, shutting every gap feels like common sense. But closing the vents for the whole season is a quick way to end up with wet windows and mouldy spots in the corners.

Most People Set Them Once and Forget Them

If you can't remember the last time you touched yours, you're in good company. In a YouGov survey in 2025, people with trickle vents were asked how often they change them:

• 31% never change the position
• 29% change them only when the seasons change
• 11% change them every day

Plenty of people open their vents in summer and close them in autumn, which is the wrong way round. In summer, you'll have the windows open anyway. In winter, the windows stay shut, so the trickle vents are often the only fresh air a room gets.

Why Do People Close Their Trickle Vents?

When the survey asked what stops people from using their trickle vents, these were the top answers:

Heat loss and draughts top the list. Both are fair concerns, and each has a better fix than shutting the vent for months.

Do Trickle Vents Waste Heat?

A little, yes. Warm, damp air has to leave for fresh air to come in, so some heat goes with it. But trickle vents are sized to let in a small, steady trickle of air, hence the name.

Compare that with what happens otherwise:

• Opening a window swaps far more air, far more quickly, and it's easy to forget to close it.
• A worn window seal leaks cold air around the sash all day and night, and you can't close it.
• Shutting everything keeps the heat in, but it keeps the moisture in too. Damp walls feel colder and take more heating, and mould is a pain to get rid of.

If cutting heat loss is the aim, start with the gaps you don't want. Replacing worn gaskets is usually the bigger win, and our Seal Centre helps you find the right profile. Then leave the trickle vents open to bring in the air you do need.

Why Is My Trickle Vent Draughty?

A working trickle vent shouldn't feel like a draught. It sits high up, so the incoming air mixes with the warm air, making any air you feel more like room temperature than a chill. If you can feel a cold blast, work through these.

What to look for:

• Is it actually the vent? Hold the back of your hand by the vent, then run it slowly around the edge of the opening sash. If the cold air is coming from the sash edge or the corners, the seal has worn, not the vent. Learn how: our winter window draught guide shows you how to track it down.
• Is the cover broken? If the slider won't close fully or the plastic has cracked, you can't control the airflow. A replacement vent costs a few pounds and takes 15 to 20 minutes to fit.
• Is it a windy side of the house? On an exposed wall, slide the vent part-way closed on rough days rather than shutting it for months.

When Is It Fine to Close Them?

• During storms, or strong winds blowing straight at that side of the house
• On the coldest nights, if a room feels chilly, as long as you open them again the next day
• While you're decorating or doing dusty work outside
• If the outside air is poor for a short time, such as smoke from a bonfire or nearby roadworks

The key word is "short". Closing them for an evening is fine.

Which Rooms Need Them Open?

• Bedrooms. You spend seven or eight hours breathing in a closed room, and 42% of people in the survey never open their bedroom window on winter nights. The vent is often the only air coming in.
• Kitchens and bathrooms, where cooking, baths, and showers produce the most moisture.
• Any room where you dry clothes.
• Rooms that already have condensation or mould. Of the people who described where their mould was, half mentioned the bathroom and 45% a bedroom.

How to Keep Trickle Vents Working

Trickle vents only work if air can get through them. Once or twice a year:

1. Slide the cover open and closed to check it moves freely.
2. Brush or vacuum out dust, cobwebs, and dead insects from the inside slot.
3. Check the outside grille isn't clogged with paint, dirt, or a spider's nest.
4. Make sure curtains and blinds aren't pressed up against the vent.

If a vent is cracked, missing its cover, or won't slide, it's time for a new one. Learn how: our step-by-step guide to fitting a trickle vent covers the whole job.

Shop Trickle Vents with GB DIY

We stock the RW Simon Premium Trickle Slot Vent for everyday rooms, the RW Simon Hi-Flow+ 525mm for rooms that steam up a lot, and the RW Simon Acoustic Trickle Vent if outside noise is the reason you keep yours shut. Have a browse through our full trickle vents range, with same-day dispatch on orders before 3 pm.

We're here to help. If your old vent is broken and you're not sure what to replace it with, send us a photo through our Part Finder, and we'll help you identify a suitable replacement. You can also give us a ring on 01623 622205 to chat through which vent suits your windows.

FAQs

Should trickle vents be open all the time?

Yes, in most homes. They're designed to give constant background ventilation, which is what keeps condensation down. Close them only for short spells in bad weather.

Do trickle vents make a room cold?

They shouldn't. Because they sit high up, the incoming air mixes with warm air before it reaches you. If a room feels cold, check the seals around the opening sash first, as worn gaskets are a more common cause.

Is it better to open a window or a trickle vent in winter?

Use both, for different jobs. Keep trickle vents open for steady background airflow, and open a window wide for a few minutes after a shower or cooking to clear the steam quickly. Our guide on how to reduce condensation on windows has more tips.

I've just had new seals fitted. Do I still need the trickle vents open?

Yes, even more so. New seals stop the draughts that used to bring fresh air in, so the vents have more work to do. Find out why you might need a trickle vent after replacing your window seals.