Continuous Mechanical Extract Ventilation Systems

By connecting a remote central fan to multiple extract valves via ductwork, continuous mechanical extract ventilation (MEV) systems constantly remove moisture-laden air from the kitchen and wet rooms. This air is then expelled from a single 125mm diameter outlet such as an external wall louvre or roof vent. As well as clearing polluted air, the system causes a drop in pressure within the property that draws fresh air in through the window ventilator.

To save time and effort, continuous MEV systems can be linked to various switches or sensors that instruct the system to boost when necessary. These include humidistats, lighting circuits, shower circuits, passive infrared motion sensors and boost switches.

These systems are simple to install during new builds or major refurbishments. They offer whole-dwelling ventilation that delivers a constant supply of fresh air at a low rate for a cleaner and more comfortable property.

How do continuous mechanical extract ventilation systems work?

Continuous MEV systems consist of three main components:

Background ventilators, such as trickle vents in windows, that provide ventilation throughout the whole building
Ducts that run from moisture-producing rooms such as the kitchen or bathroom
A centrally located mechanical extract fan that draws in wet and polluted air, expels it from the building and replaces it with fresh air from outside

The extractor fan is typically situated in a remote space such as the attic or eaves. This serves to mute the sound of continuous extraction, making continuous MEV essentially silent.

These systems are designs to operate continuously, providing a constant low level of extraction. They can also boost when necessary to provide rapid extraction, such as during cooking, showering or bathing.

One of the major advantages of continuous MEV systems is that occupants don’t need to remember to switch the ventilation on or off. They provide convenient access to clean air and also help to maintain a comfortable inside temperature in all weather and seasons.

Due to the need for ductwork throughout the building, continuous MEV systems are most commonly found in new build dwellings. This is particularly true for those with single façades or that are airtight. However, these systems can be added to existing buildings during major refurbishments.

How do continuous mechanical extract ventilation systems work?

Quickly removes wet and polluted air to purify living environments
Far more efficient that separate fans due to comprehensive ductwork reaching each wet room
Low energy requirements, allowing residents to save on their energy bills
Minimal noise disturbance, as the extraction fan operates remotely
Continuous operation means there’s no need to switch the extraction on or off
Cools the environment in hot weather by extracting hot air and drawing fresh air in
Allows for compliance with the latest building regulations, including the Homes (Fitness for Human Habitation) Act 2018 Document F