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Which ventilation principle to choose?

To achieve the optimum indoor climate for your building, it is important to start planning at an early stage which type of ventilation is best for you. Each installation has different needs. Here are some principles to consider.

One of the first choices you should make when planning a ventilation system is which principle to use. The two most common principles are: mixing and moving air (also called thermal control).

Ventilation by air mixture

For air mixing, the air diffuser is placed high in the room, near the ceiling. The blown air enters at a relatively high speed. The air is distributed throughout the room and is in principle mixed homogeneously with the ambient air. By carefully choosing the supply air diffusers, it is possible to obtain completely draft-free ventilation.


Air mixing

Air displacement ventilation

For displacement ventilation, the air diffuser is placed low in the room, at floor level. The cold supply air enters at a relatively low rate and spreads over the soil surface. As the blown air heats up, it rises upwards and pushes the ambient air which is exhausted via the exhaust air at the ceiling.


Air displacement

Adapt the ventilation according to the design of the room and the use

Which of these techniques to choose depends on many factors, for example:

  • Room size
  • Ceiling height
  • Furnishing
  • What activities are carried out in the premises

One of the most important aspects to keep in mind is that ventilation should provide good comfort in the zone of occupancy, which in layman's terms is the area in which people usually carry out their activities - from 0.1 2.0 meters above the ground.


Occupation zone

Mixture ventilation is well suited for rooms with low or medium ceilings that have high demands on comfort, for example classrooms, small restaurants and offices. As we have already explained, the blown air must enter at the level of the ceiling. Mixing ventilation can, if necessary, give a high cooling effect. On the other hand, it is less suitable for large premises with a high ceiling height where the blown air may have difficulty reaching the occupied area. It is also less suitable for activities where there is a need to exhaust ambient air instead of mixing it with the blown air, for example in operating theaters.

Displacement ventilation, on the other hand, is often a better choice for premises with medium to high ceiling heights, such as industrial premises, airports and large cafeterias. As the blown air enters at ground level, the occupied area is ventilated quickly and the existing ambient air is pushed upward. Displacement ventilation is best suited to rooms with limited cooling needs and where there are locally large heat sources, for example, restaurant kitchens. It is less suitable for use in heavily furnished rooms, where the air flow is easily blocked, and for rooms in need of heating, because the supply air is colder than the ambient air.

Choose the right ventilation principle for your project to ensure the best indoor environment quality!