In the case of decentralised ventilation systems with heat recovery (heat recovery), the ventilation unit is usually located in the room from which it is to supply fresh air or from which it is to extract the stale air.
In contrast to centralized systems, there are several individual devices that take over the air transport. A pipe system is not necessary, the air volume is either exchanged room-by-room or transported from one outer wall via an overflow area to the other outer wall.
A major advantage of decentralised ventilation systems is their room-by-room installation, which also allows for easy retrofitting in the course of an energy-efficient renovation. In most cases, a core hole is enough to integrate the device into the wall. Since, in contrast to central systems, no cable network is necessary, the maintenance and cleaning effort is limited to the device itself. This creates a cost advantage, especially for apartments and small buildings where only a few individual devices are required.
of ventilation stages according to DIN 1946-6: for better controllability of the air exchange, four different ventilation levels are defined in DIN 1946-6:
These ventilation stages offer the user the possibility of adapting the flow volume to the respective use.
Pre-temperature control of the outside air: on particularly cold winter days, the heat exchanger must be protected from icing. In the case of decentralised ventilation units, pre-heating of the outside air is only possible by means of an electric preheating coil, which creates a primary energy disadvantage compared to central systems with ground heat exchangers, for example.
Air distribution: in combined supply and exhaust air units, the air is blown in or extracted from a combined valve in different directions. To avoid short-circuit currents, it is particularly important that the device and the valve opening are correctly adjusted and have sufficiently high flow velocities. Otherwise, devices set up room-by-room can lead to poor ventilation of the more remote room areas.
When using units with reversible heat exchangers, overflow rooms are also supplied with fresh outside air due to the opposite position of the individual units on the building. It must be noted that the changeover intervals take place at sufficiently large intervals, otherwise the charging of the heat exchanger will not work optimally on the one hand and short-circuit currents may occur on the other.
Hygiene/cleaning/maintenance: due to the omission of a pipe system, cleaning is limited to the device itself. The device is pulled out of the wall for cleaning purposes, filters can be easily replaced and the WT can be cleaned.
Filtering: most filters in ventilation systems are fine dust filters, but they can also be supplemented with finer filters such as pollen filters. The filters should be inspected by the user regularly by visual inspection and changed about 1 time a year. Most systems have filters that can be changed by the user. When selecting the device, it should be noted that not too short maintenance intervals are required, otherwise there is a risk of neglecting maintenance, which means that contamination of the system is inevitable. It is important that not only the fresh outside air is filtered, but also that a filter is used on the exhaust air side in front of the heat exchanger, otherwise the WT will be polluted by house dust entered. This can lead to hygiene problems, especially with enthalpy heat exchangers.
Parallel operation of ventilation systems and fireplaces: If a ventilation system and a fireplace for solid fuels (e.g. stoves) are operated at the same time, it must be ensured that the combustion air is not taken from the room air. At the same time, it must also be prevented that flue gases from the stove are introduced into the room. Leaks in the fireplace or its supply air duct can allow these smoke gases to enter the room and, in the worst case, lead to poisoning of the users.
Regulations on this can be found in §4 of the Model Combustion Ordinance (FeuVO), which have been adopted in the combustion ordinances of the individual federal states and can be looked up there for the respective building site.
One possibility is room-air-dependent fireplaces with an external combustion air supply. In these devices, the combustion air must be supplied directly from the outside via an on-site supply air duct and at the same time a safety device with general building authority approval from the DIBT (e.g. vacuum monitor) must be installed, which monitors the air pressure conditions in the room and switches off the ventilation system in the event of negative pressure. This device configuration must be coordinated with the ventilation system manufacturer and the local chimney sweep.
Alternatively, air-independent fireplaces can be used that meet increased requirements for tightness and have a general building authority approval from DIBT. These devices are marked with a so-called "Ü mark" (conformity mark). During installation, however, attention must also be paid to the tightness of the supply air duct and the transitions to the chimney. Although a safety device to monitor air pressure is not mandatory, the tightness of the furnace must be checked regularly, which results in maintenance costs. There is a certain residual risk that leaks will occur between test intervals that go unnoticed if there is no vacuum monitor.
Sound insulation: Quiet operation of the ventilation system is crucial for user satisfaction, which is why the minimum building law requirements according to DIN 4109 are not sufficient. However, most devices fall well short of this minimum requirement, so that this does not automatically result in a restriction in the choice of product.
Protection of neighbouring residential units:
DIN 4109 regulates minimum requirements for noise from third-party residential units, whereby a sound pressure level of up to 35 dB(A) is permissible for ventilation systems without conspicuous individual tones in living and recreation rooms. It should be noted that sound pressure levels from ventilation systems of 30 dB(A) and more are not accepted by a significant number of people, so it makes sense to agree on increased sound insulation levels for the sound insulation of noise from ventilation systems both in one's own and in other residential units.
Notes onsound insulation within the residential unit:
A sound pressure level of about 25 dB(A) creates good conditions for the protection of living and recreation rooms of your own residential unit and can also be easily achieved technically.
However, sound insulation is the interplay of several factors that play a different role depending on the system design. Outside the house, noise emissions must be limited to protect the neighbors, and the local municipalities provide information on this in addition to the VDI guideline 2058. It should be noted that the requirements in residential areas are much higher than in industrial areas. Of course, the sound from outside must also be limited into the building so that the interiors are not polluted by external noise sources such as busy roads.
In the case of decentralised ventilation systems, care must also be taken to ensure that in the event of increased sound insulation requirements for the outer wall, which result from the development plan, for example, the necessary sound insulation dimensions are complied with by the installation of the device and that the device does not create too large sound bridges. If the requirements are high, a central system can be used if necessary.
rFire protection: decentralised ventilation systems may not be installed in walls that have a fire protection requirement as a room-enclosing component to the outside, in particular in fire walls and in walls that are permissible instead of fire walls.
: Both DIN and EnEV require the ventilation system to be adjusted by the specialist company carrying out the work in order to check the projected values and to be able to make any adjustments. The adjustment protocol is also an important proof of certification by the Passive House Institute.
DIN 4109: Sound insulation in building construction
DIN 4719: for ventilation of dwellings – requirements, performance tests and marking of ventilation units
DIN V 18599-6, calculation of the usable, final and primary energy requirements for heating, cooling, ventilation, domestic hot water and lighting
DIN EN 1946-6, Ventilation of apartments. Regulations and technical specifications for free ventilation, decentralised and centralised systems for exhaust air and supply and exhaust air systems.
DIN EN 12779, Ventilation of non-residential buildings - General principles and requirements for ventilation and air conditioning systems and room cooling systems
DIN EN 13779: Ventilation of non-residential buildings - General principles and requirements for ventilation and air conditioning systems and room cooling systems.
EEWärmeG 2011, Renewable Energies Heat Act (EEWärmeG 2011)
VDI Guideline 2081:Noise generation and noise reduction in ventilation and air-conditioning systems.
Source: bauwion
