Demand Control Ventilation
Demand Control Ventilation
In our series of plain English pieces we explain all about Demand Control Ventilation (DCV)
Demand control ventilation (DCV) is an intelligent ventilation method that ensures good indoor air quality and saves energy. DCV systems consist of sensors, controllers and ventilation fans. The sensors continuously measure and monitor indoor air quality and provide real time feedback to the controller.
The controller conveys the sensor information to the fans, adjusting the rate of ventilation according to what is happening in each room.
The extract fans, which are barely audible, are placed in attic spaces or utility rooms and are connected via ducts to extract grilles in wet rooms (kitchen, bathroom, utility).
Air comes into the house through humidity sensitive wall inlets in the dry rooms (bedrooms, living rooms). The system constantly varies its operation to match the usage of the house.
How do the sensors work?
There are two types of sensors used in DCV systems: humidity sensors and motion sensors. When a room is occupied its relative humidity increases. Humidity sensors detect theincrease in humidity, prompting the controller to increase airflow, which evacuatesstaleair.
Activity in kitchens, bathrooms and toilets usually increases water vapour levels, requiring fast evacuation removal of moist air. Motion sensors, which detect that someone is in a room, as well as humidity sensors, are often installed in these rooms, to ensure good ventilation.
What are the advantages of DCV?
A DCV ensures adequate, but not excessive, ventilation in the rooms that need it. It adapts, moment-by-moment, to occupants’ needs.
If a room is being used a lot the DCV ensures good ventilation. If a room is not being occupied the DCV automatically reduces air flow. By intelligently ventilating a house a DCV reduces the amount of air that needs to be warmed, thus saving heating costs. Another advantage of a DCV is that the build up of condensation and the potential for mould-growing conditions are avoided.
Do DCVs work for retrofits?
Yes. Reducing unwanted draughts is one of the key steps to making a home more energy efficient. With careful sealing around windows, doors and vents, and installation of new glazing, uncontrolled air-changes can be greatly reduced. However with effective air tightness it is vital to ensure sufficient fresh air. Our standard ventilation method of holes in the walls and some additional fans in bathrooms is unlikely to be successful at ensuring high indoor air quality. DCV guarantees this. DCV systems are easily installed in a retrofit. The DCV fans inlets can be slotted into standard ventilation holes, replacing internal and external vent covers. The DCV fans can be installed in roof spaces or utility rooms. One householder who installed a DCV as part of his SuperHomes retrofit says: ‘The demand control ventilation is very good because even though the house is air tight it is very fresh. It’s not stuffy.’