Trickle vents explained: why new windows have them
If you last bought windows more than a few years ago, the small vent strip along the top of a new frame is probably unfamiliar, and plenty of customers ask us to leave it off. Most of the time we cannot, and the reason is worth understanding before you order rather than on fitting day.
What a trickle vent is.
A trickle vent is a small closable slot built into the window frame that lets a steady trickle of fresh air through even when the window is shut. It has a flap or slider inside so you can close it down, and a cowl outside that keeps rain out.
It is not a draught, or at least it should not be. A working vent moves a small, controlled amount of air. If you can feel wind through a closed vent, the vent is open, and closing the flap is the fix.
Why the rules require them.
Since June 2022, the building regulations in England expect replacement windows to provide at least as much background ventilation as the windows they replace, and in most homes to add it where there was none. The logic is simple: modern windows seal far better than old ones, and a house that used to breathe through its leaky frames stops breathing when they are replaced.
Without background ventilation, the moisture from cooking, showers and sleeping has nowhere to go, and it shows up as condensation and mould. The vent is the regulation answer to a problem that better windows genuinely create.
Can you refuse them?
There are limited situations where vents are not required, and a survey is where that gets decided rather than a preference expressed at the quote stage. If another compliant ventilation route exists, the surveyor can take it into account.
What we will not do is leave required vents off to win an order. The installation gets certified for building regulations compliance, and the certificate matters when you sell the house.
How to live with them.
Leave bedroom vents open overnight; that is when a room generates the most moisture with the least ventilation. Close them when it is windy or cold enough to notice, and open them again after. They are there to be used, not taped over.
If a room with open vents still streams with condensation every morning, something else is going on, and it is worth a proper look rather than more gadgets.
Replacing windows?
Get the ventilation answer at survey, not after fitting.
Vent requirements are decided by the room and the regulations, and our surveyor confirms them before anything is made. Price your windows first and ask us anything at survey.
From the blog
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What actually happens when you replace windows: quote, technical survey, manufacture and fitting day, and what each stage decides. No mystery, no hard sell.
Draughty windows: repair or replace? An honest checklist
Not every draughty window needs replacing. A straightforward checklist of what can be fixed, seals, hinges and locks, and the signs the window is done.
Condensation on the outside of your windows? That's good news
External condensation on new double glazing is the glass insulating well, not a fault. What causes it, when it clears, and the one misting that is a problem.
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