Frånluffventilation

Frånluffventilation, often translated as displacement ventilation, is a method of room ventilation where fresh air is supplied at low velocity at the floor level and rises as it becomes warmer due to heat sources in the room, such as occupants and equipment. This creates a natural stratification, with cooler, cleaner air at the bottom and warmer, contaminated air rising towards ceiling exhaust vents.

Unlike mixing ventilation systems that aim to dilute contaminants throughout the entire room, frånluffventilation focuses on supplying clean air directly to the occupied zone, which is the area from the floor up to a height of approximately 1.8 meters. This approach is particularly effective in spaces with significant heat loads and localized sources of pollution, as it can lead to improved indoor air quality and thermal comfort in the breathing zone.

The design of frånluffventilation systems typically involves diffusers or grilles located near the floor, often along walls or in raised floor systems. These diffusers are designed to introduce air gently, preventing drafts and ensuring the air spreads across the floor before rising. Exhaust air is usually removed from high-level grilles or diffusers near the ceiling.

Key advantages of frånluffventilation include its energy efficiency, as it can often operate with lower fan power compared to mixing systems, and its ability to provide superior air quality in the occupied zone. However, successful implementation requires careful design to ensure proper air stratification and to avoid short-circuiting of air, where supply air is prematurely drawn into the exhaust. It is often used in applications such as offices, auditoriums, and industrial settings.