Complete Guide to Trickle Vents

In recent years, the focus in window manufacture and installation has been on energy efficiency.

This has led to windows being more airtight than ever before, thereby reducing heat loss and the carbon emissions.

However, the airtightness has presented additional concerns around ventilation which is required to maintain a healthy internal environment.

Trickle vents have been used as one solution around this.

What is a trickle vent? 

Also known as a head vent, night vent or slot vent, a trickle vent is a small vent at the top of the window unit which can be opened to allow air to slowly trickle into the home.

There are a number of options for a trickle vent: 

  • Through Frame Design: where the vent is positioned through the head of the frame
  • Over Frame Design: where the ventilation is routed above the frame of the window
  • Glazed In: where the vent is fitted into the glazing itself 

Why install trickle vents? 

Without proper ventilation, the air quality in your home will deteriorate.

Lack of air circulation will also lead to additional problems such as internal condensation.

There are a number of ways to ventilate your property.

This includes purging, in which we open a window to rapidly clear out the bad air and let fresh air enter the home; extraction, such as you might find in the bathroom; and background ventilation, where the air is gradually circulated.

Trickle vents provide background circulation. One of the key benefits to this type of ventilation is that, unlike opening a window or switching on an extractor fan, you don’t have to think about it. You just leave the vent doing its thing while you enjoy a fresh internal environment. 


Trickle vents also have the benefit of keeping your home more secure.

Leaving a window open to allow air into your home is a major security risk, even during the day while trickle vents can keep your air circulated without compromising on your home security. 


There’s no need to install a complete set of new windows as trickle vents can be installed retrospectively into uPVC window frames.

It can be a time-consuming job, but if you’re concerned about background ventilation, it could be a preferred solution to the full replacement of your windows. 

MLI Building Products are able to supply uPVC window frames complete with trickle vents, as well as trickle vent units for retrospective installation. Book an appointment to find out more.