A good ventilation system is important in any home to keep indoor 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.
An Intermittent Extract Ventilation (IEV) system uses extractor fans in the kitchen and bathrooms which turn on and off. The fans can be controlled by a timer, light switch, or sensor. Because the fans don't run continuously, an IEV system doesn't always work hard enough to ensure that a healthy home is maintained. Either a Decentralized Mechanical Extract Ventilation (dMEV) system or a Mechanical Ventilation with Heat Recovery (MVHR) unit is recommended over an IEV system wherever possible. When energy efficiency measures are planned for a home, this can also be a good time to consider upgrading existing IEV systems.