There are four types of ventilation systems, which are:  

•  System 1 back ground ventilation and intermittent extractor fans  

Extract fans are a quick way to extinguish moist from a space, such as kitchens, toilets, and utility rooms for fast intermittent air extraction.  

•  System 2 passive stack ventilation  

Passive stack relies on a natural buoyancy instead of active fans to move the air. This can give a better air movement and efficiency than air bricks or trickle vents.  

•  System 3 continuous mechanical extract ventilation (mev and dmev)  

This can be an entire build centralised system (MEV), or a localised decentralised fan system (dMEV). 

•  MEV  

Typically located in a loft space or hallway cupboard. Multiple ducts run from the unit to the kitchen, bathroom, ensuite and other wet rooms of a property to simultaneously draw moisture laden air from these wet rooms to control humidity levels. 

•  dMEV 

Individual room fans, which operate continuously to draw moisture from either the bathroom, kitchen, utility room or other wet room.  

•  System 4 Continuous Mechanical Extract Ventilation with Heat Recovery 

 MVHR is an entire dwelling ventilation system that supplies and extracts air continuously at a low rate, with the facility to be boosted as required. 

An MVHR ventilation system provides fresh, filtered air, energy efficiency and a comfortable all year round climate. Stale, moist air is extracted from the wet rooms of a home, like system 3, and fresh filtered air is injected into habitable rooms such as bedrooms, lounges, etc. Some systems also have Heat Recovery. 

The heat from the extracted stale air is drawn through an air-to-air heat exchanger located within the heat recovery ventilation unit itself, and is used to warm the incoming fresh filtered air for the habitable rooms in your property, for example living rooms and bedrooms. In some cases, around 96% of the heat generated within your property can be retained.