What is ventilation
If the natural ventilation is not sufficient for the necessary air exchange, mechanical or machine ventilation is used. With targeted air flow and one or more fans, it ensures the required air exchange rate in the room, in the apartment or in the building regardless of external influences (wind pressure / temperatures). Because of the increasingly airtight construction method, mechanical ventilation is on the advance. Modern, energy-saving ventilation systems adapt the air exchange to the respective requirements. In the German-speaking world, the term "Mechanical ventilation"Mainly used in industrial construction, while in residential construction of"mechanical ventilation " is spoken.
Central ventilation systems
A central ventilation system supplies several rooms, building wings or an entire building with fresh air via a duct network with at least one fan. It takes up a considerable amount of space and requires special measures with regard to noise and fire protection. In the Exhaust air systeme a central ventilation device sucks the stale air out of the rooms. Application examples are kitchens, guest rooms or laboratories. At the central Ventilation system on the other hand, one fan each transports the outside and exhaust air. The fans are either arranged in a compact ventilation device or separately in a supply air and an exhaust air device.
Decentralized ventilation systems
Decentralized ventilation devices such as individual fans or fan convectors only ventilate individual rooms. They can also be combined with central exhaust air systems and heat recovery via circuit systems (KVS). Decentralized devices enable a variable room design, as they are arranged on a grid. By eliminating an air duct system, lower room heights are possible.
Here the ventilation takes place naturally, without a fan. Under the influence of wind, thermal buoyancy or the weight difference of the air with temperature differences between inside and outside, the fresh outside air flows into the interior through leaky openings in the building envelope (e.g. joints or roller shutter boxes). The forces generate a volume flow of air that flows through the building and exchanges the air in the process.
Joint ventilation is the natural flow of air through gaps, holes and cracks in the building structure as well as through leaky windows and doors. This form of free / natural ventilation is also known as self-ventilation. The intensity of the joint ventilation depends on the weather conditions, especially the wind, and cannot be regulated; an even exchange of air is not guaranteed. In strong winds, the air exchange can increase fourfold. In old buildings, the hourly air change in the rooms in winter is about 0.3h⁻¹
As the name suggests, the air is exchanged by opening a window. If the window is in the tilted position for a longer period of time, it is referred to as permanent ventilation, if it is opened briefly and completely, it is called burst ventilation. Although this quickly secures the hygienically required minimum air requirement, it is associated with heat losses in winter and requires being on site. The duration of ventilation depends on the outside temperature: the colder it is outside, the less moisture there is in the outside air and the shorter the ventilation time can be. A strong ventilation effect is achieved through cross ventilation, where opposite windows and / or doors are opened. Equipped with an electric drive, the rooms can also be ventilated regularly or cooled down overnight in summer. Natural ventilation of the building without ventilation and air conditioning systems is also possible via double facades with permanently ventilated spaces. The windows or ventilation flaps must be arranged opposite one another for rapid night-time cooling.
The natural air exchange can be increased with the air flow from a duct over the roof. The shaft ventilation uses the natural buoyancy (chimney effect). An application example is the ventilation of windowless bathrooms and toilet rooms without a fan (DIN 1946-6 Ventilation technology - Part 6: Ventilation of apartments - General requirements, requirements for dimensioning, execution and labeling, handover / acceptance (acceptance) and maintenance). Each room to be ventilated must have its own air duct over the roof. The one used in old buildings in the past Berlin ventilation (Supply air through leaky window and door joints) is no longer permitted because the EnEV requires airtightness.
Roof top ventilation
The shaft ventilation can be improved by arranging ventilation attachments (suction cups) or short shafts, roof racks or roof lanterns at the highest point on a roof. This type of ventilation is mainly used in buildings with industrial use. There are usually higher temperatures in the interior, so that fresh air has to be constantly provided. In order to avoid excessive cooling in winter and excessive warming in summer, the exhaust air openings should be designed so that they can be adjusted or closed by means of adjustable flaps or blinds. A special form of shaft and roof top ventilation are systems for the natural extraction of smoke and heat (RWA).
Expertise on the subject
Air and ventilation
Room (ventilation) and indoor air quality
The main tasks of room ventilation are to ensure comfort in the rooms and to prevent structural damage from ...
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