A good ventilation system is important in any home to keep air quality high, prevent overheating, and regulate moisture levels in the air. Before installing energy efficiency measures that increase the airtightness of the home, such as insulation or draughtproofing, care must be taken to ensure that there is an adequate ventilation system in place, to prevent unintended consequences such as condensation and damp. A decentralised Mechanical Extract Ventilation system (dMEV) uses fans running continuously at a low level in the kitchen and bathrooms, to help maintain a healthy level of humidity in the home. Sensors in the fans trigger a boost, so that the fans work a little harder as required. These sensors can monitor humidity, carbon dioxide or other indoor air quality metrics. It is crucial to empower residents with information that enables them to lead healthy lives. Some form of app display of indoor air quality, with a manual boost button, can help to close this feedback loop.
Please see MVHR for a more in-depth whole house ventilation strategy.
Mechanical extract fans are installed in each wet room and exhausted to the exterior, either directly or via a short duct to an external terminal. This system is to operate continuously (24/7) without intervention from occupants and include a relative humidity (RH) sensor to automatically invoke temporary ‘boost’ facility. At least one air inlet is to be provided in each living space and bedroom, to balance the dwelling pressure, and air flow through the dwelling is to be facilitated by 10mm undercuts beneath all internal doors (or an equivalent area of ventilators installed in the doors at low level).