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Controlled Ventilation on Demand

Controlled ventilation on demand is most probably the most energy efficient and comfort centric of all ventilation method is executed correctly. In theory, the design of the system is similar to pay per use, this meaning that ventilation is constantly adjusted based on use.

It is estimated that a great deal of our office, residential and commercial ventilation is designed based on constant flow ventilation, simply said, ON/OFF system.

In most cases the ventilation is running on constant flow during the day and peak hours and partial or complete shutdown during evenings or time when the building is not being used.

In controlled ventilation on demand, the comfort and conditioning of each occupied zone is adjusted based on required volume air flow, temperature and pollution level of each zone/room.

Ventilation on demand means an individual regulation of the airflow in every occupied zone, either manually or via some form of building automation system.

Regardless of what airflows that are supplied or extracted, there must be a balance between the fan-controlled supply and exhaust airflows. This is important, among other things in order utilize the heat exchanger in an optimal way and thereby minimize the energy consumption.

This is a more energy efficient method than to let fans run all the time with constant speed.

The reason for this is that one does not use more air than necessary to get a good air quality and that one during periods when nobody stays in the dwelling only uses as much air as is needed to air out the emissions from the building. So, there are two great advantages with ventilation on demand, lower energy consumption and better air quality.

Ventilation on demand means that the design of the system changes as compared with traditional system solution. The fan speed control must be based on the principle of electronic speed control with signal from a pressure sensor placed in the duct system. The diffusers in the occupied zone must also be designed so that a change in airflow is possible. Thanks to the fact that a demand regulated system builds on a pressure being possible to maintain, we also get a third great advantage. It also helps us to avoid noise problems. Regardless of the adjustment of supply and exhaust diffuser, the pressure drop will not change and thereby we eliminate one of the prerequisites for the occurrence of sound problems.

To control the ventilation so we get the right air volume at any given moment will improve the comfort considerably. At the same time the energy will be saved as the ventilation goes down when it is not needed.

Demand ventilation can be a simple system based on time and temperature requirements of an occupied zone. To a multi sensor installation within a zone in combinations of CO2, VOC, temperature, humidity, presence and light sensors. In such systems compete room is automated to adequacy adapt to the single or multi user requirements in each zone. Such systems most commonly combine the work process of cooling, heating, ventilation and air distribution system to adapt to the use requirement and building room automation has the task to optimize the settings to reduce the needs and pressure to accommodate the right environment and reduce the energy cost per zone. In this way the maximum comfort is combined with maximum energy saving potential.


Ref: Svensk Ventilation hand book “shortness of breath”