Mechanical extract

This is the most basic form of ventilation acceptable under current building regulations and consists of single or a central extract fans taking stale or moist air from bathrooms and kitchens while using passive wall vents to supply fresh air.

Demand control ventilation

It is an improvement on mechanical extract. As the name suggests, it can be controlled to suit the demand in the dwelling. Moisture sensors on the extract side can increase the flow, and controllable wall vents can restrict the amount of unheated exterior ambient air allowed into the living space.

Mechanical heat recovery ventilation

• This is the most suitable system for energy efficient homes.
• The actual working principle is as simple as it is ingenious, one fan controls fresh air into the house and one pulls stale air out of the house. The air is not mixed but the heat from the extract air is transferred to the fresh air by heat exchangers.
• This means that no uncomfortably cold air is blown into the house in winter.
  Air is extracted from wet rooms, such as bathrooms and kitchens, where steam and moisture are generated. This extracted air is directed to the heat exchanger, where its heat is transferred to incoming fresh air. The preheated fresh air is then ducted from the exchanger to living spaces and bedrooms, ensuring efficient and comfortable ventilation.

Decentralised MHRV

• Works on the same principle but they are usually wall mounted single room vents. These extract for a set time period and store the heat from the outgoing air in a heat plate. They then expel that heat into incoming air for the same time period.
• This eliminates the need for ducting which makes them well suited for Retrofitting or buildings where a centralised MHRV is not possible.
• They require a power supply to each unit.