Trickle Vents: An Essential Guide

8 min read Windows

Window trickle vents, also known as trickle ventilators, are small openings in windows that allow a restricted flow of air into a home. While often overlooked, these vents play an important role in maintaining indoor air quality and preventing issues like mould growth and condensation. This comprehensive guide will explain everything homeowners need to know about trickle vents.

Firstly to answer a few common questions:

Are trickle vents a good idea? Yes, they will help in improving the air flow and its quality within your home

Should they be left open in the winter? By preventing condensation build up and keeping fresh air circulating in your home, especially when you’d rather not open a window in winter, it would be a good idea.

What is the law on trickle vents? From June 2022 all new homes are required to have them fitted as standard and also any new replacement windows to existing properties are required to have them fitted as mandatory to the new windows.

Do trickle vents stop damp? Yes, they can help dry out any damp and mould build ups and also assist with reducing condensation on the windows.


Now, what Are Trickle Vents and Why Are They Used?

Window trickle vents are small, unobtrusive openings fitted into window frames that allow a limited amount of ventilation. They typically have covers to keep out drafts and insects. The vents continuously allow a trickle of fresh air to flow in, hence the name.

The main purpose of installing trickle vents, is to provide background ventilation that helps remove moisture and pollutants from indoor air. They work together with mechanical ventilation systems and extraction fans to create a whole-building strategy. Trickle vents bring fresh air in, while fans expel stale, humid air out. This constant air exchange regulates humidity and prevents condensation from forming on cold surfaces.

Trickle Vents

How Do Trickle Vents Work?

Trickle vents utilise the natural movement of air to bring in fresh outdoor air. As warm, stale air rises and escapes through extraction vents, it creates a slight vacuum. This pulls in replacement air from outside through any available trickle vents.

Even a tiny opening makes a surprising difference. Although the airflow is restricted, opening just a few vents per room provides enough fresh air for a whole building. The vents generally stay open at all times, with covers to limit drafts. This maintains continuous ventilation.

The small inlet size serves an important function. Large openings would allow air to rush in too quickly, creating uncomfortable drafts. Restricting the size controls air speed while still permitting ample air flow. The vents are carefully engineered to optimise venting performance.

Trickle Vents

Understanding the Different Types

There are a few common types of trickle vents to choose from:

  • Glazpart has three trickle ventilation systems, the Standard Tricklevent, the Slimline Tricklevent and the Link Vent.
  • The Link Vent system is a NFA 2022 Winner and NFA 2023 Finalist!
  • Designed for use on all window types (UPVC, Aluminium and Timber), Excellent UV colour stability and with 1000’s of colour decoration options, delivered in any combination or packaging requirement.
  • With standard colours:White, Dark Brown, Black and Oak Brown.
  • Stock colours: Cream, Anthracite Grey, Chartwell Green.
  • Wood grain print effects for Irish Oak, Golden Oak, Mahogany and Rosewood.
  • Developed in 2 sizes the vents performance will be 5000 EQA and 2500 EQA. Equivalent area (EQA) is used instead of free area for the sizing of trickle ventilators as it is a better measure of a ventilators air flow performance.
  • The vents are designed to meet the requirements of building regulations, Approved document F1 2010 (Means of ventilation) whilst delivering a product to meet the needs of today’s ventilation and window markets.
  • Paint spraying of ventilators from our stock to ANY RAL, BS colour a colour swatch matching service is also available Link Vent.
  • In addition to position and size, vents differ in material. Plastic and metal are common options. Each has pros and cons regarding durability, aesthetics, and ventilation performance.
Trickle Vents

What Are the Benefits?

Trickle vents offer several advantages that make them a smart addition to any home.

Improved Air Quality

The primary benefit is improved indoor air quality. Trickle vents dilution pollutants like VOCs, radon, and excess humidity. This creates a fresher, healthier living environment. Stale, polluted air is constantly replaced with new air.

Preventing Condensation and Mold

By regulating indoor humidity, trickle vents help prevent condensation from forming on windows, walls, and other surfaces. This condensation can lead to mold growth and damage like peeling paint or plaster. Trickle vents are an important tool for controlling condensation.

Unobtrusive Background Ventilation

Unlike noisy, drafety windows, trickle vents provide subtle, draft-free ventilation. They generally go unnoticed while working away in the background. Homeowners don’t have to remember to open windows or manually turn on fans.

Trickle Vents

What Are the Potential Drawbacks?

While very useful, trickle may vents also have some potential disadvantages to consider:

  • Improper Installation – If placed improperly, the vents can allow vehicle exhaust or other outdoor pollutants to enter. Proper placement is important.
  • Provide Minimal Security – The openings may allow bugs to enter if not covered properly. Covers help prevent this.
  • Possible Source of Drafts or Noise – Poorly designed or placed vents can create annoying drafts or noise from the airflow. Careful engineering is required.
  • Require Ongoing Maintenance – The openings need occasional cleaning, and covers/filters may need replacing over time. Maintenance is required to keep them working well.

When and How Should Trickle Vents Be Used?

Trickle vents should be incorporated into any whole-house ventilation strategy. They are recommended for nearly all buildings, including homes, schools, offices, and municipal buildings. Specific applications include:

  • New construction projects to maintain a healthy living environment and air quality.
  • Renovations of older homes to reduce humidity and refresh stale air.
  • Any space prone to condensation or mold growth due to excess moisture.
  • Bedrooms, bathrooms, kitchens, and other high-humidity areas.

For optimal performance, vents should generally be left open at all times to create constant airflow. Covers prevent drafts but sometimes vents may need closed during extremely cold or windy weather. Otherwise, the subtle air exchange should run continuously.

Vents should be positioned where replacement air is needed most, like moisture-prone areas. They can be placed high on walls or discretely fitted into window frames. Proper placement is critical to prevent backdrafting or drawing in contaminants. Professional installation is recommended.

Trickle Vents

Key Design Considerations

Several factors go into engineering an effective trickle vent:

Size: The inlet holes must balance adequate airflow against draft prevention. Around 8000 mm2 is typical for domestic spaces.

Position: Vents should be placed where fresh air is needed most, while avoiding outdoor pollutants.

Noise Reduction: Internal baffles and exterior hoods minimise noise from rushing air.

Filtration: Filters block dust, pollen, and bugs without restricting airflow.

Appearance: Vents should blend in discreetly with minimal visual impact.

The careful canopy design optimises air quality and functionality while minimising drawbacks. Expert engineering is recommended.

How Trickle Vents Integrate with Overall Window Ventilation

Trickle vents play an integral role in a building’s overall ventilation strategy. While mechanical systems and extractor fans expel air, trickle vents provide the crucial inlet capacity.

For windows, a trickle vent offers subtle background ventilation, while the window frame itself provides supplemental venting. For example, a bathroom window may have an integrated vent for continuous humidity control. Opening the window widely provides a temporary boost in air exchange as needed.

They also help make opening windows more effective. Without inbound replacement air from vents, open windows tend to push indoor air out without pulling much outdoor air in. The combination creates an effective push-pull system.

Trickle Vents


Case Study: Trickle Vents in a Passive House Retrofit

Sheerwater Glass constantly undertakes renovations of all shapes, ages and sizes of homes across Surrey, Hampshire and Berkshire. Installing Glazpart trickle vents throughout to reduce condensation and improve air quality.

One such house suffered from high humidity and persistent condensation. With its tight envelope, the home required ventilation strategies. Trickle vents provided continuous, draft-free air exchange to control moisture.

Strategically placed vents reduced condensation within the first weeks. The client also noticed improved air freshness and indoor comfort. By preventing moisture buildup, the retrofit also protects the home from mold growth.

Do You Need Trickle Vents?

Trickle vents provide an easy way to maintain healthy indoor air in any home or building. They naturally dilute pollutants and humidity without the need for occupant intervention or energy consumption.

If your home suffers from stuffiness, lingering odours, condensation, or signs of mold, trickle vents are likely a smart addition. They naturally complement mechanical ventilation to create a robust air quality system. New-build homes benefit from incorporating vents from the start.

Be sure to have vents professionally installed for optimal placement and noise reduction. With proper setup, trickle vents offer set-and-forget whole-building ventilation. Contact us today for a free quote on installation or replacements for your home.


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